Wastewater in the USA & WWTP in the City of Norman, Oklahoma State

Prepared by : Ahmed H. Hilles Supervisor : Prof. Khalil Tubail

Institute of Water and Environment, Al-Azhar University, P.O.Box1277, Gaza City, Palestine

2011

Master of Water and Environment Science

Course of Wastewater Treatment

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Table of Contents Page

Table of Contents………………………………………………………. IList of Figures………………………………………………………….. IIList of Tables…………………………………………………………... IIList of Acronyms………………………………………………………. IIIPreface…………………………………………………………………. 1

1. Introduction ……………………………………………………………. 21.1 About the United States ……………………………………………. 21.2 Climate ………………………………………………………………. 3

2. History of the Water supply and sanitation in the USA……………….. 32.1 Sanitation until 1948…………………………………………………. 42.2 After 1948: Enter the federal government…………………………… 5

3. Technical and environmental overview of sanitation in the USA ……. 63.1 Water Sources ……………………………………………………… 63.2 Water Use…………………………………………………………… 73.3 Water scarcity and climate change ………………………………….. 83.4 Pollution ……………………………………………………………... 83.5 Access ……………………………………………………………….. 83.6 Water Supply and Sanitation in the USA……………………………. 93.7 Recycling of wastewater in USA…………………………………….. 10

3.7.1 Water recycling drivers and in the USA……………………………... 113.7.2 Typical Recycled Water Uses………………………………………. 113.2.3 Wastewater as source of pollution in the USA ……………………… 113.7.4 Contamination and Impacts………………………………………….. 11

4. Treatment of Municipal wastewater in the USA……………………… 124.1 Electricity consumption GHGs, and Related Emissions……………. 124.2 Social and Economic Impacts……………………………………….. 13

5. Norman City WWTP in Oklahoma State:……………………………... 135.1 General Information ………………………………………………… 13

5.1.1 Geography…………………………………………………………… 135.1.2 Topography………………………………………………………….. 135.1.3 Climate………………………………………………………………. 145.1.4 Demographics and Income…………………………………………. 14

5.2 Wastewater Treatment Plant in the City of Norman ………………... 155.2.1 Existing liquid Processes units ……………………………………... 165.2.2 Solids Handling Units:………………………………………………. 19

5.3 Existing Wastewater Treatment Facility Evaluation………………... 205.3.1 Liquid Processes Units ……………………………………………… 215.3.2 Solid Handling Processes……………………………………………. 235.3.3 Existing Solid Handling Facilities …………………………………. 245.3.4 Sludge Storage and Disposal………………………………………… 25

5.4 Future wastewater Treatment Alternatives ………………………… 255.4.1 Alternatives for Wastewater Treatment…………………………….. 255.4.2 Expansion of Existing WWTP………………………………………. 265.4.3 Construct New WWTP to Discharge to South Canadian River…….. 265.4.4 Expand WWTP and Construct New WWTP with Effluent Reuse ….. 26

6. ACKNOWLEDGMENTS.……………………………………………. 277. References ……………………………………………………………. 27

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List of FiguresPage

Figure 1.1: Map of the 50 states of the United States ………………………………… 3 Figure 3.1 : Potential For water recycling in USA…………………………………….. 10 Figure 3. 2 : Projected water recycling growth in USA……………………………….. 10 Figure 5.1: Oklahoma State and Norman WWTP location…………………………... 14 Figure 5.2 : Norman City WWTP with All Facilities …………………………………. 15 Figure 5.3.: Biotowers in WWTP………………………………………………………. 17 Figure 5.4 : Primary Clarifiers………………………………………………………….. 17 Figure 5.5: Aeration basins on the left and final clarifiers on the right ……………... 18 Figure 5.6 : Layout of the WWTP in Norman City…………………………………….. 20

List of TablesPage

Table 5.1 : City of Norman WWTP OPDES Permit Limitations………………………. 16 Table5.2: Major Plant Components……………………………………………………... 18 Table 5.3 Major Solid Handling Component …………………………………………... 20 Table 5.4 Sludge Generation Rates………………………………………………………. 24 Table 5.5 Solids Handling Component Capacity and Condition ……………………… 24

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List of Abbreviation

WWTP wastewater treatment plantUSA United States of America D.C. District of Columbiakm2 square kilometerGDP gross domestic productEPA Environmental Protection Agency CWSRF Clean Water State Revolving Fund m³ cubic meter l/c/d liter per capita per day CSO combined sewer overflows POTWs Publicly Owned Treatment Works CWA Clean Water Act UV ultravioletGHGs Greenhouse gases Tg teragrams Gg gigagrams WWTF wastewater treatment facility MGD million gallons per dayODEQ Oklahoma Department of Environmental Quality OPDES Oklahoma Pollution Discharge Elimination System DMR discharge monitoring reportsCBOD5 carbonaceous biochemical oxygen demand TSS total suspended solids NH4-N ammonia nitrogen DO dissolved oxygen BTs biotowers RBCs rotating biological contactorsRAS return activated sludgeWAS waste activated sludge scfm standard cubic feet per minute HP horsepower SWD side water depth IAWQ International Association on Water Quality lb/day/ft³ pound mass per square foot per day WRF water reclamation facility AWT advanced wastewater treatment

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Preface: The greatest challenge in the water and sanitation sector over the next two decades will be the implementation of low cost sewage treatment that will at the same time permit selective reuse of treated effluents for agricultural and industrial purposes” (Looker, 1998). It is crucial that sanitation systems have high levels of hygienic standards to prevent the spread of disease. Other treatment goals include the recovery of nutrient and water resources for reuse in agricultural production and to reduce the overall user-demand for water resources (Rose, 1999).

In order to achieve ecological wastewater treatment, a closed-loop treatment system is recommended. Many present day systems are a “disposal-based linear system”. The traditional linear treatment systems must be transformed into the cyclical treatment to promote the conservation of water and nutrient resources. Using organic waste nutrient cycles, from point-of-generation to point-of-production, closes the resource loop and provides an approach for the management of valuable wastewater resources. Failing to recover organic wastewater from urban areas means a huge loss of life-supporting resources that instead of being used in agricultural for food production, fill rivers with polluted water or other surface eater resources and even the groundwater. The development of ecological wastewater management strategies will contribute to the reduction of pathogens in surface and groundwater to improve public health. “The goal of ecological engineering is to attain high environmental quality, high yields in food and fiber, low consumption, good quality, high efficiency production and full utilization of wastes”(Rose, 1999).

In the Palestinian Territories the situation is more devastated and deteriorated particularly in Gaza Strip, the water and wastewater sector suffers from many constrains and faces an enormous amount of challenges that make it more and more complicated.

The absence of clear responsible and qualified body to organize this sector in the time of the Israeli siege and the low awareness among the Gazans, the wastewater problem become the most important issue want an immediate solutions.

There is a clear lack of financial and experiences support in this sector in Gaza Strip, which will put a new load on the Gaza Strip environment and its purification capacity in a side, and in another side the Gazans suffer from access to healthy and abundant water resources, the suitable wastewater treatment work will provide a sufficient resource of water for at least the agricultural activities and will mitigate the excessive pumping and overexploitation of the groundwater as a lone source of drinking water in Gaza Strip.

This report will shed the light on the wastewater sector in the biggest example in all over the world, it is very important issue to see how the Americans deal with their wastewater, the report will illustrate a general view about the overall situation in the USA, and will explain the wastewater treatment technique in the City of Norman within Oklahoma State in details.

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1. Introduction:

1.1 About the United States The United States of America (also referred to as the United States, the U.S., the USA, or America) is a federal constitutional republic comprising fifty states and a federal district as it shown in the figure 1.1 (US Map/ hist-geo.co). The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to the east and Russia to the west across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country also possesses several territories in the Caribbean and Pacific.

At 3.79 million square miles (9.83 million km2) and with over 310 million people, the United States is the third or fourth largest country by total area, and the third largest both by land area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries (Adams ,2001). The U.S. economy is the world's largest national economy, with an estimated 2009 GDP of $14.3 trillion (a quarter of nominal global GDP and a fifth of global GDP at purchasing power parity ( International Monetary Fund, 2010).

Indigenous peoples of Asian origin have inhabited what is now the mainland United States for many thousands of years. This Native American population was greatly reduced by disease and warfare after European contact. The United States was founded by thirteen British colonies located along the Atlantic seaboard. On July 4, 1776, they issued the Declaration of Independence, which proclaimed their right to self-determination and their establishment of a cooperative union. The rebellious states defeated the British Empire in the American Revolution, the first successful colonial war of independence (Dull, 2003). The current United States Constitution was adopted on September 17, 1787; its ratification the following year made the states part of a single republic with a strong central government. The Bill of Rights, comprising ten constitutional amendments guaranteeing many fundamental civil rights and freedoms, was ratified in 1791.

In the 19th century, the United States acquired land from France, Spain, the United Kingdom, Mexico, and Russia, and annexed the Republic of Texas and the Republic of Hawaii. Disputes between the agrarian South and industrial North over states' rights and the expansion of the institution of slavery provoked the American Civil War of the 1860s. The North's victory prevented a permanent split of the country and led to the end of legal slavery in the United States. By the 1870s, the national economy was the world's largest (Cohen, 2004). The Spanish–American War and World War I confirmed the country's status as a military power. It emerged from World War II as the first country with nuclear weapons and a permanent member of the United Nations Security Council. The end of the Cold War and the dissolution of the Soviet Union left the United States as the sole superpower. The country accounts for 40% of global military spending and is a leading economic, political, and cultural force in the world(USA Today, 2007).

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Figure 1.1: Map of the 50 states of the United States (USA)/ US Map/ hist-geo.co

1.2. Climate � The U.S. climate is temperate in most areas, tropical in Hawaii and southern Florida, polar in Alaska, semiarid in the Great Plains west of the 100th meridian, Mediterranean in coastal California and arid in the Great Basin. Its comparatively generous climate contributed (in part) to the country's rise as a world power, with infrequent severe drought in the major agricultural regions, a general lack of widespread flooding, and a mainly temperate climate that receives adequate precipitation.

Following World War II, the West's cities experienced an economic and population boom. The population growth, mostly in the Southwest, has strained water and power resources, with water diverted from agricultural uses to major population centers, such as Las Vegas and Los Angeles. According to the California Department of Water Resources, if more supplies are not found by 2020, residents will face a water shortfall nearly as great as the amount consumed today ( International Monetary Fund, 2010).

2. History of the Water supply and sanitation in the USA

In the 19th century numerous American cities were afflicted with major outbreaks of disease, including cholera in 1832, 1849 and 1866 and typhoid in 1848 (Lubowsk, 2009). The fast-growing cities did not have sewers and relied on contaminated wells within the city confines for drinking water supply. In the mid-19th century many cities built

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centralized water supply systems. However, initially these systems provided raw river water without any treatment. Only after John Snow established the link between contaminated water and disease in 1854 and after authorities became gradually convinced of that link, water treatment plants were added and public health improved. Sewers were built since the 1850s, initially based on the erroneous belief that bad air (miasma theory) caused cholera and typhoid. It took until the 1890s for the now universally accepted germ theory of disease to prevail.

However, most wastewater was still discharged without any treatment, because wastewater was not believed to be harmful to receiving waters due to the natural dilution and self-purifying capacity of rivers, lakes and the sea. Wastewater treatment only became widespread after the introduction of federal funding in 1948 and especially after an increase in environmental consciousness and the up scaling of financing in the 1970s. For decades federal funding for water supply and sanitation was provided through grants to local governments. After 1987 the system was changed to loans through revolving funds.

2.1. Sanitation until 1948

Most of the first sewer systems in the United States were built as combined sewers (carrying both storm water and sewerage). They discharged into rivers, lakes and the sea without any treatment. The main reason for choosing combined sewers over separate systems (separating sanitary sewers from storm water drains) was a belief that combined sewer systems were cheaper to build than separate systems. Also, there was no European precedent for successful separate sewer systems at the time (Lubowsk, 2009). The first large-scale sewer systems in the United States were constructed in Chicago and Brooklyn in the late 1850s, followed by other major U.S. cities (Lubowsk, 2009).

Few wastewater treatment facilities were constructed in the late 19th century to treat combined wastewater because of the associated difficulties. There were only 27 U.S. cities with wastewater treatment works by 1892, most of them "treating" wastewater through land application. Of these 27 cities, 26 had separate sanitary and storm water sewer systems, thus facilitating wastewater treatment, because there was no need for large capacities to accommodate wet weather flows. Furthermore, there was a belief that the diluted combined wastewater was not harmful to receiving waters, due to the natural dilution and self-purifying capacity of rivers, lakes and the sea (Lubowsk, 2009). In the early 20th century a debate evolved between those who thought it was in the best interest of public health to construct wastewater treatment facilities and those who believed building them was unnecessary. Nevertheless, many cities began to opt for separate sewer systems, creating favorable conditions for adding wastewater treatment plants in the future (Lubowsk, 2009).Where wastewater was being treated it was typically discharged into rivers or lakes. However, in 1932, the first reclaimed water facility in the U.S. was built in Golden Gate Park, San Francisco, for the reuse of treated wastewater in landscape irrigation.

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2.2. After 1948: Enter the federal government

In the first half of the 20th century water supply and sanitation were a local government responsibility with regulation at the state level; the federal government played almost no role in the sector at that time. This changed with the enactment of the Federal Water Pollution Control Act of 1948, which provided for comprehensive planning, technical services, research, and financial assistance by the federal government to state and local governments for sanitary infrastructure. The Act was amended in 1965, establishing a uniform set of water quality standards and creating a Federal Water Pollution Control Administration authorized to set standards where states failed to do so (Lubowsk, 2009).

Comprehensive federal regulations for water supply and sanitation were introduced in the 1970s, in reaction to an increase in environmental concerns. In 1970 the Environmental Protection Agency (EPA) was created. In 1972, the Clean Water Act was passed, requiring industrial plants to proactively improve their waste procedures in order to limit the effect of contaminants on freshwater sources. In 1974, the Safe Drinking Water Act was adopted for the regulation of public water systems. This law specified a number of contaminants that must be closely monitored and reported to residents should they exceed the maximum contaminant levels allowed. From then on, drinking water systems were closely monitored by federal, state, and municipal governments for safety and compliance with existing regulations ( Hanlon and Larry, 2007).

The Clean Water Act set the unprecedented goal of eliminating all water pollution by 1985 and authorized massive expenditures of $24.6 billion in research and construction grants. The funds initially provided an incentive to build centralized wastewater collection and treatment infrastructure instead of decentralized systems (Lubowsk, 2009). However, the 1977 amendments to the Clean Water Act required communities to consider alternatives to the conventional centralized sewer systems, and financial assistance was made available (Lubowsk, 2009).

In the mid-1990s decentralized systems served approximately 25 percent of the U.S. population, and approximately 37 percent of new housing developments (Perkins, 2007).There were disagreements between the federal government and local government about the appropriate level of wastewater treatment, with the former arguing for more stringent standards. For example, in the late 1980s, the City of San Diego and the Environmental Protection Agency (EPA) were involved in a legal dispute over the requirement to treat sewage at the Point Loma Wastewater Treatment Plant to secondary standards. The City prevailed, saying that it saved ratepayers an estimated $3 billion and that process had proved successful in maintaining a healthy ocean environment. The city’s Point Loma Wastewater Treatment Plant uses an advanced primary process (Morin, 2008). The requirement to perform secondary treatment on wastewater before ocean discharge was waived by the EPA in 1995, "taking into account the city's unique circumstances" (SDI Group, 2001).

In 1987 Congress, through the Water Quality Act, passed an amendment of the Clean Water Act, abolishing construction grants and replacing them by a system of subsidized

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loans using the Clean Water State Revolving Fund (CWSRF). The intention at the time was to completely phase out federal funding after a few years. Funding peaked in 1991 and continued at high levels thereafter, despite the original intentions. New challenges arose, such as the need to address combined sewer overflows for which EPA issued a policy in 1994. In 1997 Congress established the Drinking Water State Revolving Fund, building on the success of the CWSRF, in order to finance investments to improve compliance with more stringent drinking water quality standards.

3. Technical and environmental overview of water supply and sanitation in the USA (Infrastructure):

The centralized drinking water supply infrastructure in the United States consists of dams and reservoirs, well fields, pumping stations, aqueducts for the transport of large quantities of water over long distances, water treatment plants, reservoirs in the distribution system (including water towers), and 1.8 million miles (2.88 million km) of distribution lines (Smithsonian Institution, 2009). Depending on the location and quality of the water source, all or some of these elements may be present in a particular water supply system. In addition to this infrastructure for centralized network distribution, 14.5% of Americans rely on their own water sources, usually wells (McClure, 2008 and Wilson, 1993).

The centralized sanitation infrastructure in the U.S. consists of 1.2 million miles (1.92 million km) of sewers - including both sanitary sewers and combined sewers, sewage pumping stations and 16,024 publicly-owned wastewater treatment plants (National Park Service, 2006).In addition, at least 17% of Americans are served by on-site sanitation systems such as septic tanks (Republican Study Committee, 2005)

Publicly owned wastewater treatment plants serve 189.7 m people and treat 32.1 billion gallons (122 million m³) per day, 9,388 facilities provide secondary treatment, 4,428 facilities provide advanced treatment, and 2,032 facilities do not discharge, There are 176 facilities that provide a treatment level that is less than secondary, these include facilities with ocean discharge waivers, and treatment facilities discharging to other facilities meeting secondary treatment or better, 880 facilities receive flows from combined sewer systems (National Park Service, 2006). About 772 communities in the U.S. have combined sewer systems, serving about 40 million people (Smithsonian Institution, 2007).

3.1. Water sources About 90% of public water systems in the U.S. obtain their water from groundwater. However, since systems served by groundwater tend to be much smaller than systems served by surface water, only 34% of Americans (101 million) are supplied with treated groundwater, while 66% (195 million) are supplied with surface water (Maddison, 2006).

For a surface water system to operate without filtration it has to fulfill certain criteria set by the EPA under its Surface Water Treatment Rule, including the implementation of a

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watershed control program. The water system of New York City has repeatedly fulfilled these criteria (Meltzer, 1992).

3.2. Water use Public water supply used 43 billion gallons (163 million m³) per day in 2000 serving 242 million people, corresponding to 21% of total water use in the same year (Xinhua News Agency,2009; Shah and Anup, 2009).

Residential water use accounts for 66% of publicly supplied water in the United States, (Air Force Magazine, 2009), with the remainder being used by offices, public buildings, businesses and industry that does not have its own water sources. Residential end use of water in the United States is equivalent to more than 1 billion glasses of tap water per day. Total water use was 161 gallons (608 liter) per capita per day in 1996–1998, excluding leakage. Fifty-eight percent is used outdoors for gardening, swimming pools etc., corresponding to 101 gallons (382 liter) per capita per day, and 42% is used indoors, corresponding to 60 gallons (226 liter) (The World Factbook, 2009). The arid West has some of the highest per capita residential water use because of landscape irrigation (Department of Defense, 2008).

Indoor use falls into the following categories:

• body cleanliness: o 31% Toilets o 2% Baths o 19% Showers

• washing: o 25% Clothes Washers o 2% Dishwashers

• 18% Faucets • 3% Other Domestic Uses (The World Factbook, 2009).

Per capita residential water use in the United States is more than four times as high as in England (150 l/c/d) (Department of Defense, 2010) and five times as high as in Germany(126 l/c/d) (Ikenberry, 2004).

� Only a very small share of public water supply is used for drinking. According to one 2002 survey of 1,000 households, an estimated 56% of Americans drank water straight from the tap and an additional 37% drank tap water after filtering it (Department of Defense, 2010). 74% of Americans said they bought bottled water (Department of Defense, 2010). According to a non-representative survey conducted among 216 parents (173 Latinos and 43 non-Latinos), 63 (29%) never drank tap water. The share is much higher among Latinos (34%) than among non-Latinos (12%). The study concluded that many Latino families avoid drinking tap water because they fear it causes illness, resulting in greater cost for the purchase of bottled and filtered water (Hennessey et al., 2010).

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3.3. Water scarcity and climate change

With water use in the United States increasing every year, many regions are starting to feel the pressure. At least 36 states are anticipating local, regional, or statewide water shortages by 2013, even under non-drought conditions (Department of Defense, 2009).

According to the National Academies, climate change affects water supply in the U.S. in the following ways:

• Rising water demands. Hotter summers mean thirstier people and plants. In addition, more evaporation from reservoirs and irrigated farmland will lead to faster depletion of water supplies.

• Increased drought. Scientific evidence suggests that rising temperatures in the southwestern United States will reduce river flows and contribute to an increased severity, frequency, and duration of droughts.

• Seasonal supply reductions. Many utilities depend on winter snow pack to store water and then gradually release it through snowmelt during spring and summer. Warmer temperatures will accelerate snowmelt, causing the bulk of the runoff to occur earlier and potentially increasing water storage needs in these areas (Dull$2003).

3.4. Pollution

Sewer overflows, Combined sewer overflows (CSO) and sanitary sewer overflows affect the quality of water resources in many parts of the U.S. About 772 communities have combined sewer systems, serving about 40 million people, mostly in the Northeast, the Great Lakes Region and the Pacific Northwest (Smithsonian Institution, 2007). CSO discharges during heavy storms can cause serious water pollution. A 2004 EPA report to Congress estimated that there are 9,348 CSO outflows in the U.S., discharging about 850 billion gallons of untreated wastewater and storm water to the environment (World Bank, 2006).

EPA estimates that between 23,000 and 75,000 sanitary sewer overflows occur each year, resulting in releases of between 3 and 10 billion gallons of untreated wastewater (World Bank, 2006). The increased frequency and intensity of rainfall as a result of climate change (Conference Board, 2010) will result in additional water pollution from wastewater treatment, storage, and conveyance systems(Conference Board, 2010). For the most part, wastewater treatment plants and combined sewer overflow control programs have been designed on the basis of the historic hydrologic record, taking no account of prospective changes in flow conditions due to climate change(Conference Board, 2010).

3.5. Access

More than 99% of the U.S. population has access to "complete plumbing facilities", defined as the following services within the housing unit:

• Hot and cold piped water,

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• Bathtub or shower, and • Flush toilet.

However, more than 1.7 million people in the United States, 670,986 households, still lack basic plumbing facilities. More than a third of them have household incomes below the federal poverty level. They are spread across all racial and ethnic categories, but they are more prominent in the minority groups. Most of the people who lacked plumbing services were elderly, poor, and living in rural areas. Alaska has the highest percentage of households without plumbing 6.32 percent of all its households (Starr and Paul, 2008).

3.6. Water supply and sanitation in the United States Issues that affect water supply and sanitation in the United States include water scarcity, pollution, a backlog of investment, concerns about the affordability of water for the poorest, and a rapidly retiring workforce. Increased variability and intensity of rainfall as a result of climate change is expected to produce both more severe droughts and flooding, with potentially serious consequences for water supply and for pollution from combined sewer overflows (Maddison, 2006). Droughts are likely to particularly affect the 66 percent of Americans whose communities depend on surface water(Cohen,2004). As for drinking water quality, there are concerns about disinfection by-products, lead, perchlorates and pharmaceutical substances, but generally drinking water quality in the U.S. is good.

Cities, utilities, state governments and the federal government have addressed the above issues in various ways. To keep pace with demand from an increasing population, utilities traditionally have augmented supplies. However, faced with increasing costs and droughts, water conservation is beginning to receive more attention and is being supported through the federal Water Sense program. The reuse of treated wastewater for non-potable uses is also becoming increasingly common. Pollution through wastewater discharges, a major issue in the 1960s, has been brought largely under control.

Water supply and wastewater systems are regulated by state governments and the federal government. At the state level, health and environmental regulation is entrusted to the corresponding state-level departments. Public Utilities Commissions or Public Service Commissions regulate tariffs charged by private utilities. In some states they also regulate tariffs by public utilities. At the federal level, drinking water quality and wastewater discharges are regulated by the United States Environmental Protection Agency, which also provides funding to utilities through State Revolving Funds (USA Today, 2007, National Archives, McClure, 2008)

Most Americans are served by publicly owned water and sewer utilities. Eleven percent of Americans receive water from private (so-called “investor-owned”) utilities. In rural areas, cooperatives often provide drinking water. Finally, up to 15 percent of Americans are served by their own wells (Wilson, 1993, Zimmer, 2005).

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Water consumption in the United States is more than double that in Central Europe, with large variations among States. In 2002 the average American family spent $474/month on water and sewerage charges (U.S. Census Bureau), which is about the same level as in Europe. The median household spent about 1.1 percent of its income on water and sewerage.

3.7. Recycling of wastewater in USA: Municipal effluent in the USA equal about 35 billion gallons (132.3 million m³) /day, only 9.8% if that amount currently recycled as it shown in figure 3.1 , (Lori, 2009).

Figure 3.1 : Potential For water recycling in USA

The wastewater recycling process in the USA will reach about 11.9 billion gallons (45 million m³ /day in 2015 as it shown in figure 3. 2 ,(Lori, 2009).

Figure 3. 2 : Projected water recycling growth in USA

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3.7.1. Water Recycling Drivers in the United States • Drought-resistant or drought-proof supply • Reliable water supply enhances economy • Population growth/increasing demand for water • Preserving limited drinking water supplies • Ecosystem and environmental protection • Wastewater disposal issues • Economically feasible • Well-established technology • Sound public policy • Integrated water planning

3.7.2. Typical Recycled Water Uses

• Landscape irrigation • Agricultural irrigation • Industrial and commercial • Non-potable urban uses (toilet flushing in high-rise offices) • Environmental uses • Groundwater recharge • Potable water supply augmentation

3.2.3 Wastewater as source of pollution in the USA:

Since the early 1970s,effluent water quality has been improved at Publicly Owned Treatment Works (POTWs) and other point source discharges through major public and private investments prescribed by the Clean Water Act (CWA). Despite the improvement in effluent quality, point source discharges continue to be a significant contributor to degradation of surface water quality. In addition, much of the existing wastewater infrastructure, including collection systems, treatment plants and equipment, has deteriorated and is in need of repair or replacement (EPA, 2009).

3.7.4. Contamination and Impacts

Pollutants contaminate receiving water via many pathways: point sources; non-point sources, air deposition, agriculture; sanitary sewer overflows; Storm water runoff; combined sewer overflows; and hydrologic modifications, channelization and dredging.

A 2004 report to Congress by the EPA classifies 44% of river and stream miles, 64% of lake acres, 30% of estuarine square miles, and 93% of Great Lakes shoreline miles as impaired (unacceptable for designated uses).

Households not served by public sewers (approximately 20%) usually depend on septic tanks to treat and dispose of wastewater. Failing septic systems may contaminate surface and groundwater (Census Bureau, 2008).

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4. Treatment of Municipal Wastewater in USA: • By 2004, an estimated 21,604 POTWs were in operation treating 34.4 billion

gallons (130 mm of wastewater daily. 98% were municipally owned and provided wastewater collection, treatment and disposal service to 229 million people – 78% of the 2004 U.S. population (EPA, 2004).

• 1 billion gallons per day (3.78 l/d) of treated wastewater is reclaimed to meet nonpotable water needs, such as irrigation of golf courses and public parks (Solley et al., 1998). However, use of reclaimed water is becoming more common, particularly in the fast-growing southwest region.

• A 1998 estimate predicts that U.S. wastewater treatment systems generated nearly 8 million dry tons of sludge in 2005. This sludge requires significant energy to treat, ranging from 30-80% of total electrical energy input to a wastewater treatment system. (WEF, 2002).

• Chlorination is the most common means of disinfection in the U.S. Chlorination is usually followed by dechlorination with sulfur dioxide to avoid deteriorating ecological health of the receiving stream and the production of carcinogenic by-products.

• Ultraviolet (UV) disinfection is the most common alternative to chlorination and has comparable energy consumption .

• Chemical additions of ferric salts and lime enhance coagulation and sedimentation processes for improved solids removal as well as removal of toxic pollutants. However, their production and transport have life cycle impacts.

• Classes of unregulated organic compounds known as “emerging organic contaminants” are becoming a concern for water treatment engineers. These contaminants, including pharmaceuticals, cosmetics, hormones, nanomaterials, and others, have been shown to have adverse effects on aquatic life and may pose a potential risk for humans. Some of these chemicals are endocrine disruptors, a class of compounds that perturb the normal functioning of endocrine systems including those that affect growth, reproduction and behavior. Studies are ongoing to determine risks and potential solutions for these contaminants. Many of these chemicals pass through POTWs (SBW, 2002).

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4.1. Electricity Consumption, GHGs, and Related Emissions • Nearly 4% of the nation’s electricity use goes towards moving (80%) and treating

water/wastewater (EPRI, 2002). • In 2000, energy-related emissions resulting from POTW operations, excluding

organic sludge degradation, led to a global warming potential of 15.5 teragrams (Tg) CO2- equivalents (CO2-eq.), an acidification potential of 145 gigagrams (Gg) SO2 equivalents, and eutrophication potential of 4 Gg PO4, equivalents (EPRI, 2000).

• CH4 and N2O are mainly emitted during organic sludge degradation by anaerobic bacteria in the soil environment, wastewater treatment plant, and receiving water body.

• In 2006, an estimated 23.9 and 8.1 Tg CO2-eq. of CH4 and N2O, respectively, resulted from organic sludge degradation in wastewater treatment system, over 0.4% of total U.S. GHG emissions (EPA, 2009).

• On Average, Energy Costs Represent 7% OF Wastewater Utilities’ Operating Budgets.

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4.2. Social and Economic Impacts Population growth and urban sprawl increase the collection (sewer) system needed to move wastewater to centralized treatment plants. Although the 50-year life expectancy of a sewer system is longer than that of treatment equipment (15 to 20 years), renovation needs of a sewer system can be more costly. If there is no renewal or replacement of existing sewer systems (estimated by the American Society of Civil Engineers to be about 600,000 miles ( 960,000 km) of publicly owned pipe), the amount of deteriorated pipe will increase from 10% to 44% of the total network from 1980 to 2020. The estimates (in 2004 dollars) of U.S. clean water needs for building new and updating existing wastewater treatment plants, sewer maintenance/construction, and combined sewer overflow corrections were $69.0, $77.8, and $54.8 billion, respectively (EPA, 2008).

5. Norman City WWTP in Oklahoma State:

5.1. General Information

Norman is a city in Cleveland County, Oklahoma, United States, and is located 20 miles (30 km) south of downtown Oklahoma City as it shown in 5.1 . It is part of the Oklahoma City metropolitan area. As of 2010, Norman was estimated to have 115,876 full-time residents, making it the third-largest city in Oklahoma and the 234th-largest city in the United States. It is the county seat of Cleveland County and is the county's center for business and employment (U.S. Census Bureau, 2009).

5.1.1. Geography

Norman is located at 35°13′N 97°25′W / 35.2217°N 97.4183°W / 35.2217; -97.4183 (35.2216, -97.4182).

The city has a total area of 189.5 square miles (491 km2), of which 177.0 square miles (458 km2) is land and 12.5 square miles (32 km2) or 6.60% is water. Approximately 27 square miles (70 km2) are developed urban area.�

5.1.2. Topography

Norman and the surrounding areas are mostly flat. The terrain in the western section of Norman is prairie while the eastern section, including the area surrounding Lake Thunderbird, consists of some 6,000 acres (24 km2) of lakes and Cross Timbers forest. The lowest point within city limits is approximately 970 feet (296 m) above sea level (located at 35.20388N, 97.17735W). The highest point is approximately 1,245 feet (379 m) above sea level (located at 35.21266N, 97.39000W) (U.S. Census Bureau, 2009).

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Figure 5.1: Oklahoma State and Norman WWTP location

5.1.3. Climate

Norman lies in a temperate, sub-humid climate, with frequent variations in weather daily and seasonally, except during the consistently hot and humid summer months. Consistent winds, usually from the south or south-southeast during the summer, help temper the hotter weather. Consistent northerly winds during the winter can intensify cold periods.

The summer can be extremely hot, as was evident in 2006 with a few-weeks span of nearly 110 °F (43 °C) temperatures. The average temperature is 61.3 °F (16.3 °C), though colder though the winter months, with a 37.8 °F (3.2 °C) average in January, and warmer during the summer months, with an 82.2 °F (27.9 °C) average in July. The city receives about 35.4 inches (900 mm) of precipitation annually (Weather Base, 2009).

Norman lies within Tornado Alley and has a severe weather season lasting from March through August, with peak activity in April and May. Tornadoes have occurred during every month of the year. The Oklahoma City metropolitan area, including Norman, is one of the most tornado-prone areas in the United States. As recently as May 10, 2010, a tornado outbreak occurred in southeastern Norman that resulted in the loss of multiple homes and businesses (National Weather Service, 2009).

5.1.4. Demographics and Income

As of the census of 2009, there were 95,694 people, 38,834 households, and 22,562 families residing in the city. The population density was 540.6 people per square mile

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(208.7/km²). There were 41,547 housing units at an average density of 234.7/sq mi (90.6/km²).

The median income for a household in the city was $36,713, and the median income for a family was $51,189. Males had a median income of $35,896 versus $26,394 for females. The per capita income for the city was $20,630. About 7.8% of families and 15.0% of the population were below the poverty line, including 11.4% of those under age 18 and 5.7% of those age 65 or over (U.S. Census Bureau, 2009).

5.2.Wastewater Treatment Plant in the City of Norman (Camp&McKee, 2007) :

The City of Norman Wastewater Treatment Facility (WWTF) as it shown in figure 5.2 (Google-Imagery,2011) provides treatment to wastewater generated by a population of over 100,000. Originally constructed in 1942, the facility has undergone additional significant facility upgrades during 1957, 1963, 1972, 1986, 1990, 1999 and 2007.

Currently, the facility’s secondary treatment capacity is designed for an average flow of 12 million gallons per day (MGD)(46,000 m³/d), a sustained wet weather flows of 15 MGD (57 m³/d) and a maximum daily flow of 30 MGD (114 m³/d) .

Figure 5.2 : Norman City WWTP with All Facilities (Google-Imagery,2011)

The Oklahoma Department of Environmental Quality (ODEQ) administers the issuance and enforcement of municipal discharge permits, known as Oklahoma Pollution Discharge Elimination System (OPDES) permits. The United States Environmental Protection Agency (USEPA) however, maintains oversight rights for ODEQ’s water quality programs. �

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The City of Norman Wastewater Treatment Facilities is required, as part of the OPDES permit to routinely monitor effluent water quality and report conventional pollutant loading on Norman’s segment of the Canadian River (receiving stream). These monitoring reports are called Discharge Monitoring Reports (DMR) and are required monthly for treated effluent and annually for biosolids treatment and agricultural land application .

5.2.1. Existing liquid Processes units (Camp&McKee, 2007):

The facility receives raw influent wastewater which is treated sufficiently to meet or exceed quality standards required by an OPDES permit. The OPDES permit establishes maximum limits on carbonaceous biochemical oxygen demand (CBOD5), total suspended solids (TSS) and ammonia nitrogen (NH4-N), and a minimum limit on dissolved oxygen (DO). The permitted limits for these constituents vary by season and are listed in Table 5.1.

Table 5.1 : City of Norman WWTP OPDES Permit Limitations(Camp&McKee, 2007)

Effluent Characteristics

November – March

(mg/L)

April – May

(mg/L)

June – October

(mg/L)

CBOD5 25 13 13

TSS 30 30 30

NH3-N 12 4.5 5

DO 5 5 5

Preliminary treatment consists of an existing headworks facility and influent parshall flumes. Primary treatment is accomplished by four primary clarifiers. Secondary Treatment consists of biotowers (BTs) and rotating biological contactors (RBCs) in parallel with activated sludge treatment in aeration basins, followed by final clarifiers. Sludge produced from the various processes is thickened and stabilized with gravity thickeners and anaerobic digesters, respectively as it shown in figure 5.3 and 5.4 .

The Secondary Treatment process is operated in a parallel/series arrangement with approximately 30 percent of the primary effluent flowing through the BT/RBC treatment train, while the remaining 70 percent of the primary effluent is treated in the aeration basins as it shown in figure 5.5. Effluent from the BT/RBC train flows into the last third of the aeration basins for polishing, NH4-N removal, and toxicity reduction. The combined AS/RBC mixed liquor then flows by gravity to the final clarifiers.

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Figure 5.3.: Biotowers in WWTP (Google-Imagery,2011).

Figure 5.4 : Primary Clarifiers (Google-Imagery,2011).

There are four final clarifiers as it shown in figure 5.5, two 126 feet (38 m) diameter by 7.25 feet (2.2 m) deep, and two 125 feet (38 m) diameter by 14.5 feet (4.4 m) deep. Hydraulically, approximately one third of the total flow is diverted to the 126-foot final clarifiers and two-thirds to the 125 foot final clarifiers. Flow diversion is controlled by flow-splitting following the aeration basins. Sludge removed from the final clarifiers is categorized as return activated sludge (RAS) or waste activated sludge (WAS). RAS is returned to the head of the aeration basins and WAS is pumped back to the head of the plant for removal in the primary clarifiers(Camp&McKee, 2007).

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Figure 5.5: Aeration basins on the left and final clarifiers on the right (Google-Imagery,2011).

Table 5.2 includes an itemized listing of major plant components related to the liquid treatment process. The various components are listed by treatment stage, treatment process, and component description.

Table5.2: Major Plant Components (Camp&McKee, 2007)

Stage Process Component

Flow Equalization

1- Flow Equalization Basin; 15.8 MG Capacity (60,000 m³) 1- Blower Building; 3- 30 HP Blowers at 850 scfm 2- 75 HP, EQ Basin Mixing Pumps; 2- 20 HP Stormwater Transfer Pumps

Pump Stations 3 - 72-inch (183 cm) Screw Pumps, 20 MGD (76,000 m³)

Prel

imin

ary

trea

tmen

t

Headworks

1 - Manually-Cleaned Bar Screen 1 - Mechanically-Cleaned Bar Screen 1 - 2 HP Comminutors 2 - Aerated Grit Chambers: 40ft.x 35ft. x 12ft.Deep (12,10.5,3.6 m respectively)

Prim

ary

Trea

tmen

t

Primary Clarifiers

2- 70 ft.(21 m) Diameter Primary Clarifier, SWD -10 ft (3m) 2- 60 ft (18 m) Diameter Primary Clarifier, SWD -9.5 ft.(2.7m)

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Stage Process Component

Secondary Pump Station

2 — 50 HP, VFD Vertical Turbine Pumps 1 - 75 HP, Vertical Turbine Pump

Fixed Film Processes

2 —60 ft. (18m) Diameter Biotower, 15 ft (4.5 m)Bed Depth 2— RBC Basins! 115,000 ft³ (34,500 m³) by 6 ft (2 m)Deep

Activated Sludge Process

3- Aeration Basins at 184 ft. x 40 ft. x 18 ft. Deep (55, 12, 5.4, respectively) 1 — Blower BIdg., 4-350 HP Blowers at 6,550 scfm (2000 m³/minute)

Secondary Clarifiers

2 — 126 ft.(38m) Diameter Secondary Clarifier, SWD = 7.25 ft (2.1m). 2 — 125 ft. (37.5m)Diameter Secondary Clarifier, SWD = 14.5 ft. (4.3 m). S

econ

dary

Trea

tmen

t

RAW/WAS Pump Station 2 —60 HP, VFD. Vertical Turbine Pumps

Sludge Thickening

4— 18ft.(5.4 m) Diameter Gravity Thickeners, SWD = 10 ft. (3m)

Anaerobic Digestion

4—70 ft. (21m )Diameter Anaerobic Digesters, SWD 22. ft. (6.6m)

Sol

idH

andl

ing

Supernatant Pretreatment

2—Aeration Basins at 30ft. x 79 ft. x 14.5 ft. Deep (9, 23.7, 4.35 m respectively)

5.2.2 Solids Handling Units:

At the Norman WWTP, sludge is produced from primary sedimentation and the generation of biological sludge resulting from the conversion of organic materials to cellular mass. Influent wastewater flow is transported to the headworks by a combination of pumping and gravity flow. Biological sludge is added to the flow prior to the aerated grit chambers. The combined sludge and influent suspended solids are removed from the liquid treatment process in the primary clarifiers. Once introduced into the primary clarifiers, the solids combine and are removed by gravity forming a sludge blanket. From the primary clarifiers, sludge is pumped to gravity thickeners for further treatment.

Four gravity thickeners are used to further concentrate primary sludge. Once concentrated, primary sludge is pumped to either of the two primary anaerobic digesters. Sludge entering the digesters is stabilized anaerobically, where the volatile percentage of the sludge is broken down into CO2, methane and water. Secondary digesters are used for solid/liquid separation and storage purposes. Water generated from the process is removed from the digesters as supernatant. Gas generated, containing CO2 and methane, is used in the production of electricity with a natural gas/digester gas-driven engine and generator.

After adequate solid detention time, digested sludge is transferred to the secondary digesters for storage, prior to final disposal. The City currently disposes of its stabilized

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sludge by applying it as a liquid to agricultural land. This has been the disposal practice for years and appears to be the most economical and environmentally friendly option for disposal (Camp&McKee, 2007).

Table 5.3 includes an inventory of solids handling processes currently utilized at the facility. Additionally, the condition of each component has been rated dependant on age and condition.

Table 5.3 Major Solid Handling Component (Camp&McKee, 2007)

Process Component Condition

Sludge Thickening

4-18ft.(5.4m) Diameter Gravity Thickeners , SWD = 10ft.(3m) Poor

Anaerobic Digestion

4 – 70 ft.(21m) Diameter Anaerobic Digesters, SWD = 22 ft.(6.6m) Good

Supernatant Pretreatment

2 – Aeration Basins @ 30 ft. X 79 ft. 14.5 ft. Deep

(9, 23.7, 4.35 m respectively) Good

5.3. Existing Wastewater Treatment Facility Evaluation � As part of the current report, it is important to understand the components that make up the treatment works and the associated capacities of each unit. Figure 5.6 includes a treatment plant schematic that identifies each component of the plant The following paragraphs include a breakdown of each major plant component and the current available capacity for the component.

Figure 5.6 : Layout of the WWTP in Norman City (CDM, 2007)

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5.3.1 Liquid Process Units (Camp&McKee, 2007)

The current wastewater treatment plant consists of three overall process stages: preliminary treatment, primary treatment, and secondary treatment. Each phase of treatment acts as a removal mechanism for targeted pollutants in the influent wastewater stream, (forth process is a solid sludge handling).

Preliminary treatment at the Norman farcicality consist of mechanical bar screen, a comminutor, and a manual bar screen grit catcher. The West Side Lift Station also utilizes a bar screen. Currently the comminutor operates poorly; therefore, the bar screens are used to remove stringy materials, such as plastic bags, large wooden objects, and any other material that could damage downstream process equipment.

When referring to bar screen capacity, velocity through the screen becomes the limiting factor. According to Oklahoma DEQ (ODEQ), the maximum allowable velocity through a bar screen is 3 fps (1m/s). The design capacity should be between 1.5 fps (0.5 m/s) and 3 fps (1m/s); therefore, the current average daily flow is well within the acceptable range.

The second process in the preliminary treatment stage utilizes aerated grit chambers. The current grit chambers are retrofitted pre-aeration basins which have a volume of approximately 120,000 gallons (454 m³) and a length/width ratio of 1.75/1. ODEQ, Title 252, Chapter 655 criteria suggests a detention time of three minutes. Although the current volume and regulated detention time would allow a peak flow of 57,6 MGD (218,000 m³), the current hydraulic capacity would not allow a flow greater than approximately 24 MGD (91,000 m³) without overflowing the walls of the headworks.

Two parshall flumes separate the preliminary treatment phase from the primary treatment phase. The flumes are used to control the flow diverted to two sets of primary clarifiers (discussed below). The flumes together are rated for approximately 24 MGD (91,000 m³) in their current configuration; however, the current utilization of parshall flumes to control flow split to the primary clarifier is not a desirable method. A more reliable method of splitting flow would be the utilization of fixed length rectangular weirs. The use of weirs results in a system that provides a more reliable flow split over wider ranges of flow and results in less head loss.

Considering the current condition and hydraulic capacity of the existing preliminary treatment units, it is recommended that new facilities be constructed to replace the current bar screening facility, grit removal facility, and parshall flume flow splitting facility. At a minimum, the new facility should be sized to handle the current design capacity of subsequent treatment process units. Redesign of the preliminary process treatment units should also consider planned expansions to the subsequent treatment processes. That is, the new facilities should be expandable to meet future WWTP capacity needs over the planning horizon.

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Primary treatment at the Norman facility is accomplished in two sets of primary clarifiers that operate in parallel. One set consists of two circular clarifiers, constructed in 1964, each with a diameter of 60 feet (18m) and a depth of 9.5 feet (2.8m). The second set, constructed in 1957, consists of two 70 ft. (21m) diameter circular clarifiers with a depth of 10.7 feet (3.2m) Clarified effluent flow from the primary clarifiers overflows to secondary treatment, while the primary sludge is removed from the bottom of the clarifiers and conveyed to solids handling facilities.

The current clarifiers appear to be in fair condition and working efficiently. Typical removal efficiencies for circular primary clarifiers, under design flow conditions, is approximately 65 percent TSS removal and 30 percent BOD removal. Design criteria for primary clarifiers are based on hydraulic loading; therefore, current capacity is based on maximum overflow rates allowed by the ODEQ, the current design (based on max month flow) and peak (based on 2 hour peak flow) hydraulic capacity of the existing four primary clarifiers is 13.4 MGD (50,000 m³) and 20 MGD (76,000 m³), respectively.

To account for any loss in removal efficiency during flows in excess of 13.4 MGD(50,000 m³), the secondary treatment facility has been slightly oversized to handle excess loading that may pass through the primary clarifiers under slightly overloaded conditions. Expansion of primary treatment will be dependent on the projected increase in flow over the planning horizon.

Secondary treatment accomplishes the conversion of soluble organic material into settleable solid biomass. Organic material, which would not settle in a primary clarifier, is introduced into a biological inventory of microorganisms where the organisms uptake the organic material and convert it to cellular mass. Once the soluble organic material is converted, the mass is settled in a final or secondary clarifier. At the Norman plant two types of systems are used to convert organic materials to cellular mass; fixed film and suspended solids processes. By design, approximately 30 percent of primary effluent is pumped to the fixed film process.

The remaining 70 percent of primary effluent is conveyed to the suspended growth process. Capacity of the biological system is dependent on both hydraulic capacity and mass loading.

The current capacity of the fixed film processes (BTs & RBCs) is 5,630 lbs per day BOD. and 714 lbs per day of ammonia. In determining the fixed film capacity, ammonia is the limiting constituent. Hydraulic loading of the fixed film processes is well within ODEQ, Chapter 655 guidelines. Based on these criteria, hydraulic capacity of the fixed film process is 3.6/4.5 (Average Day/Max Month or AD/MM) MGD.

The suspended growth process, or activated sludge, is capable of handling 70 percent of the primary effluent. This is equivalent to 15,900 lbs of BOD per day and 1,736 lbs of ammonia per day. ODEQ, Chapter 655 includes criteria for detention time and mass loading. Based on the criteria, the new activated sludge process will have a hydraulic

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capacity of 105 MGD (400,000 m³)and a 21 MGD (80,000 m³)peak flow capacity. Adding the 8.4/10.5 (AD/MM) MGD hydraulic capacity of the activated sludge process with the 3.6/4.5 (AD/MM) MGD hydraulic capacity of the fixed film process results in a total AD/MM hydraulic capacity of 12/15 MGD for this section of the process flow. Expansion of these facilities will be dependent on projected future loadings to the secondary process.

The final process in secondary treatment is the removal of biomass from the treated wastewater in the final clarifier prior to discharge to the South Canadian River. Four circular clarifiers are used in the separation process where biomass settles out of the water and is pumped back to the head of the biological process for reuse.

Secondary clarifier capacity is regulated with much flexibility in the ODEQ design criteria without consideration of clarifier depth or clear water zone. As such, criteria from the International Association on Water Quality (IAWQ) were used for determining current capacity. Based on the IAWQ criteria, the secondary clarifiers have a combined design flow capacity of 18.6 MGD (70,000 m³)and a peak flow capacity of 35 MGD(132,000 m³).

5.3.2 Solids Handling Processes (Camp&McKee, 2007)

The results of successful liquid treatment yield residual sludge which must be treated and disposed in accordance with federal and state regulations. Sludge (biosolids) from the Norman WWTP is generated by the removal of combined suspended solids in the clarification process. Following clarification, biosolids produced from the liquid portion of the wastewater treatment plant is concentrated in gravity thickeners and stabilized by anaerobic digestion prior to land application. Plant production reports for the period from December 1999 through September 2004, were reviewed to determine current sludge production from the WWTP.

Data from operating reports and mass balance calculations indicate that sludge generated by the liquid process train ranges between 1,750 (787 kg) and 2,050 pounds (928 kg) dry sludge/(MGD(3780 m³) influent to the WWTP), which is typical for this type of process. For the purposes of this process review, it is recommended that an average sludge production rate of 1,900 pounds/MGD (855 kg) be used. Using this sludge generation rate in conjunction with an average volatile solids content of approximately 73 percent, a volatile solids reduction rate of 60 percent in the digesters, and taking into account the supernate drawoff, yields a sludge generation rate of 1,068 pounds (481 kg)dry sludge/(MGD influent to the WWTP) produced for land application. Table 5.4 summarizes the estimated dry tons of sludge produced for land application based on various influent flow scenarios.

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Table 5.4 Sludge Generation Rates (Camp&McKee, 2007)

Scenario Description

Annual Average Influent Flow Rate

(MGD)

Sludge Generation For Land Application (Dry

Tons/Day)

Jan 2000- October 2000 Annual average flow based on

operation reports 9.58 5.12

Existing, Approved, and Contractual 2006 13.9 7.42

Future 2012 20.5 10.95

5.3.3. Existing Solids Handling Facilities (Camp&McKee, 2007)

Primary sludge is conveyed to one of four gravity thickeners, where sludge settles to the bottom of the thickener and clarified decant is discharged to the head of the plant. Each of the four thickeners is 18 feet (6m) in diameter providing a total surface area of 1018 ft² (306 m³) . ODEQ, Chapter 655 criteria limits both mass and hydraulic loading on the basis of surface area. The mass loading and hydraulic loading to the gravity thickeners at the design annual average flow of 12 MGD (46,000 m³) are approximately 22.4 lb/ft²/d, and 120 gallons/ft²/d, respectively. The mass loading is exceeding the maximum loading allowed by ODEQ criteria at 16 lb/ft²/d. the units are below the minimum hydraulic loading (400 gallons/ ft²/d) outlined in the criteria. Future wastewater characteristics will push loadings even further beyond the allowable limit, requiring the addition of dewatering and thickening processes. Current capacity of the thickeners is. summarized below in Table5.5.

Table 5.5 Solids Handling Component Capacity and Condition (Camp&McKee, 2007)

Sludge Treatment

Phase Parameter

Hydraulic Capacity

(GPD)

Mass

Capacity

Design

Criteria

Overall condition of Facility

Thickening Gravity Thickeners 712,600 16,288٭ ODEQ Poor

Stabilization Primary Digesters 84,500 13,550٭٭ ODEG Good

Storage Secondary Digesters 50٭٭٭ - - Good

Notes:

٭ gallons / ft² / d lbs of Volatiles / day ٭٭ days ٭٭٭

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Thickened sludge is pumped to one of two primary digesters where it is held for a minimum of 15 days for stabilization. During stabilization, the volatile solids are broken down into inert material, CO2, methane and water. On average, sludge concentration from the thickeners to the primary digesters is approximately 3.5 percent with a volatile content of 73 percent. The capacity of anaerobic digesters is a function of solid retention time and the concentration of volatile solids. According to the WRF Manual of Practice Na 8.4th Edition, typical design sustained peak volatile solids loading rates range from (0.12 to 0.16 lb/day/ft³. Volatile solids loading rates less than 0.08 lb/day/ft³ result in inefficient digester operation. This manual recommends a minimum solids retention lime of 15 days. To maintain the balance of solids retention time and the proper volatile solids concentration at the future flow rates, additional thickening will be required. 5.3.4. Sludge Storage and Disposal Currently the anaerobic digestion process has in excess of 30 days of storage capacity. Available storage capacity provides a buffer when sludge cannot be applied to the land due to weather, farming operations, or mechanical breakdown. Thirty days may seem to be an excessive amount of storage; however when cumulative generation rates are compared to cumulative application rates, the storage requirements have repeatedly approached and, at times exceeded, 30 days. In fact, cold and/or wet weather periodically prevents land application of the sludge for 60 to 90 days. An increase in the needed storage versus what is currently available appears to be warranted for both the Existing and Future scenarios.

5.4. Future wastewater Treatment Alternatives Recently, several studies assume all influent flow continues to be conveyed to the plant- Although the existing plant could be expanded to accommodate future flows, the cost associated with infrastructure necessary to convey the future flows (interceptor relief lines) would require a tremendous amount of capital. Additionally, the growth in Norman is to the north, away from the existing WWTP, making the cost of conveyance for future flows even more costly. When considering the cost associated with conveying all of the wastewater to the current WWTP, it may be more cost effective to build a new wastewater treatment facility in the direction of current growth. The existing WWTP is located in the far southern portion of Norman adjacent to the South Canadian River. If a new facility were to be constructed, it would be likely that it would be built somewhere along the Little River, in the northern portion of Norman. The construction of a new facility would lead to many new options for reusing the treated effluent, rather than discharging it into the South Canadian River. 5.4.1 Alternatives for Wastewater Treatment Several feasible alternatives exist and a refined list has been developed. Development of the alternatives was based on physical constraints, such as stream loading limits of the South Canadian River, effluent discharge requirement into the Little River, as well as reuse options available to the City. The preliminary list of alternatives for future wastewater treatment follows.

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5.4.2.Expansion of Existing WWTP (Camp&McKee, 2007):This alternative includes expansion of the existing WWTP by providing the necessary

infrastructure to convey all flows to the current plant site. The current assimilative capacity of the South Canadian River is based on discharge limits associated with a maximum discharge of 16 MGD (60,000 m³). Essentially, once the flows to the existing plant reach 16 MGD (60,000 m³), the permit limits will become more stringent due to the fixed mass loading to the river. Once 16 MGD (60,000 m³) is surpassed, plant components, which provide additional advanced wastewater treatment (AWT) in the form of filtration units, would have to be constructed to meet the stringent permit limits. The cost associated with the additional AWT at the facility could run from around $1.50 to as high as $2.00 per gallon of treatment capacity. The cost for AWT does not include costs associated with construction of new facilities to increase the facility’s capacity to, or above, 16 MGD (60,000 m³). Costs associated with increasing the capacity of the current plant would include unit costs for increased sludge handling capabilities. These unit costs may be as high as $3.00 per gallon of treatment capacity. Not withstanding the cost of conveying additional flows to the plant, this alternative would be costly to implement. 5.4.3. Expand WWTP and Construct New WWTP to Discharge to South Canadian River

Instead of conveying all new flows across town to the existing plant. a new WWTP would be constructed in northern Norman to handle flows from the growing portion of the community. Discharge from the existing plant would be maintained at its current location, while discharge from the new WWTP would likely be to the South Canadian River, approximately 12 river miles upstream from the current discharge point. This alternative would include costs to expand the existing facility up to 17 MGD(65,000 m³). The new facility would be somewhat more expensive due to land acquisition requirements and the need for effluent pumping and transmission from the new plant site to the South Canadian River. This alternative would allow the City to build-out the existing WWTP to 17 MGD(65,000 m³) and begin the planning process for siting, financing, designing and constructing a new WWTP in northern Norman. It would also allow interceptor improvements to be downsized to reflect a future decrease in flows to the southern WWTP. 5.4.4. Expand WWTP and Construct New WWTP with Effluent Reuse

Instead of conveying all new flows across town to the existing plant, a new WWTP would be constructed in northern Norman. Effluent from the existing facility would be discharged to the South Canadian River in accordance with applicable OPDES permit requirements. Effluent from the new facility would be reused for industrial needs, agricultural needs, or to augment Lake Thunderbird. This alternative would include costs to expand the current facility up to 17 MGD(65,000 m³). The type of reuse or effluent limitations would determine costs for a new facility. If the effluent were discharged to the Little River to supplement the water supply in Lake Thunderbird, the WWTP would have to provide advanced wastewater treatment. However, if reuse were limited to industrial use, such as cooling water or irrigation for agricultural land, the plant would be limited to AWT requirements, which would cost less. The cost for the "two plant scenario” is

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somewhat higher than for expanding an existing plant due to additional land purchase needs. A very attractive option for this alternative would be to utilize wetlands treatment following AWT to accomplish advanced treatment in lieu of adding expensive treatment process units for AWT. This combination of reuse and treatment would allow the City to enjoy a wetlands environment, while supplementing the City’s water supply by allowing flow from the wetlands to enter the Little River and eventually reach Lake Thunderbird. The costs for wastewater treatment would be consistent with AWT costs. Costs for developing a wetlands treatment system would have to be added to the total cost; however, the costs associated with a wetlands system would be less expensive than AWT through mechanical processes. Although. technically this is an attractive option. this approach would require the approval by the Central Oklahoma Master Conservancy District and ODEQ to discharge effluent into the Little River drainage basin. To date, discharges of this nature have not been allowed. Additionally. Lake Thunderbird supplies drinking water to the citizens of Midwest City and Del City, as well as to Norman citizens. Discharges that would ultimately affect this water supply would require approval by each of these entities. 6. ACKNOWLEDGMENTS: This report was performed with sincere and heartfelt supports from the appreciated Prof. Khalil Tubail, instructor of the Wastewater Treatment, Reclamation & Reuse Course, Master of Water and Environment Science, Al-Azhar University – Gaza. All thanks and appreciation to Prof. Tubail for his great efforts in order to develop and support the water and environmental situation here in Gaza Strip. His continued support is gratefully acknowledged. �

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