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During the past two decades, increasing attention has been given to the nexus of water and energy and the maintenance of adequate supplies (Voinov & Cardwell, 2009). A key feature of sustainable urban development is minimization of the carbon footprint of the urban water cycle in order to curtail global changes in the climate (Solomon et al, 2007). Water quality cri-teria and reporting requirements are established for urban water cycle segments through use of codified regulations, guidelines, industry standards, and uniform practices (Roberson, 2011; Copeland, 2010; Marsalek et al, 2006; Iranpour et al, 2004; Pontius, 2003, 1990). Corresponding requirements for minimiza-tion of energy and associated greenhouse gas (GHG) emissions are still lacking because water-sector carbon emissions are neither regulated nor monitored in most regions of the world (GAO, 2011). However, voluntary reporting is increasing in support of internal stewardship programs and in anticipation of pending regulatory limits or carbon cap-and-trade programs. In many instances, reporting is based on use of less germane protocols, methodologies, tools, and reporting strategies developed for other sectors (McGuckin et al, 2013). The objective of GHG reporting is to determine emissions of a baseline operational performance level in order to inform future decision-making that strives to achieve reductions (WRI/WBCSD, 2005). It is therefore important that the measurement and reporting of the baseline and subse-quent operational strategies use methodologies, tools, and system controls that assess GHG emissions in a consistent and document-able manner. Comparability will also assist with benchmarking efforts. To date there is little information in the literature that collectively addresses the options available to minimize GHGs from direct-process emissions or from nonrenewable energy use within the urban water cycle. Thus the objective of this article is

to assess the availability of relevant and appropriate tools for managing segments of the urban water cycle for energy minimiza-tion and GHG emissions accountancy. A better understanding of this issue will show the remaining gaps that prevent optimized practices and will provide a better understanding of future mon-itoring and reporting needs for accurate GHG emissions accoun-tancy in support of emissions reduction strategies.

GHG REPORTING FRAMEWORK FOR THE URBAN WATER CYCLE

The urban water cycle is shown schematically in Figure 1. This cycle demonstrates the movement of water into, within, and out of defined urban boundaries that contain the engineered systems for potable water production, wastewater processing, and stormwater management. Potable water systems convey, store, and extract raw water for treatment and distribution whereas wastewater systems collect, treat, discharge, and/or reclaim wastewater. Stormwater management focuses on pollutant removal and flow reduction in order to protect water resources and minimize flooding (Daigger, 2009). Low-impact develop-ment (LID) technologies reduce urban stormwater runoff and its pollution load (Pataki et al, 2011). LIDs also reduce GHG emissions by contributing to local potable and nonpotable sup-plies using less energy for treatment and distribution. However, the majority of information on GHG reductions is focused on water and wastewater; little is available on stormwater. GHG reporting by the water sector is mandated in limited regions (e.g., Ofwat in England/Wales and Northern Ireland Authority for Utility Regulation in Northern Ireland; Prescott, 2009) or for specific portions of wastewater facilities (e.g., coverage by the US Environmental Protection Agency of municipal waste-

The water–energy nexus has motivated water industry professionals to maintain water performance goals with less energy input and fewer greenhouse gas (GHG) emissions. This article investigates protocols, methodologies, and tools for energy and GHG emissions control and tracking that are adaptable to or specifically developed for use within the urban water cycle. Although many operational energy-minimization strategies are available, real-time or near real-

time tools for monitoring and reporting of energy use and GHG emissions are not yet widely developed for the water sector. Additional study is warranted to obtain a better understanding of process-specific emission factors and real-time measurement and control of activity levels associated with emissions. It may also be beneficial for the water industry to consider a continually updated compendium of GHG emission-estimation methodologies.

Urban water-cycle energy use and greenhouse gas emissionsJOAN OPPENHEIMER,1 MOHAMMAD BADRUZZAMAN,1 ROBYN MCGUCKIN,1 AND JOSEPH G. JACANGELO1

1MWH, Arcadia, Calif

Keywords: urban water cycle, energy management tools, greenhouse gas emissions, water industry energy use, water–energy nexus, water treatment carbon emissions

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water treatment facility–operated landfills; USEPA, 2012). Although the water and wastewater treatment industry produces GHG emissions that reside below most current regulatory reporting limits, a summary of global regulations that could trigger reporting requirements for the water sector in the future is provided in Table 1.

Granularity of GHG accounting. GHG-emissions reporting for any sector derives from a protocol that provides an organiza-tional framework for the emission sources and a methodology that defines quantification processes. Tools provide software-driven algorithms that translate input parameters to the output variables needed to report in accordance with a prescribed methodology. There are three levels of granularity for GHG accounting that can be selected by a water utility. The sponsor-ing entities and features of each level and their applicability for use within the urban water cycle are summarized in Table 2. The United Nations Intergovernmental Panel on Climate Change (IPCC) has created a globally accepted top-level methodology

for country-level estimation of GHGs from major sectors of the economy that includes portions of the wastewater sector. The IPCC approach is the closest globally harmonized approach to GHG emissions, but it is a top-down approach lacking the necessary detail for application to many design and operational aspects within the urban water cycle. The underlying emissions equation in the IPCC methodology (Eq 1) uses a top-down approach of national averages for the emission factor and site estimations of the activity data.

Emission Rate = Emission Factor × Activity Data (1)

This type of accounting uses broadly generalized functions and look-up constants, and lacks the specificity and ability to trace specific facility-level changes offered by bottom-up, facility-spe-cific algorithms derived from empirical data or fundamental process modeling that a bottom-level tool specific to the water industry will provide. Mid-level methodologies provide guidance

one column �gure width on-line 20 picasor 3.5 inches

Remove this information

two column �gure width 44 pica or 7.25 inches

Raw water

Conveyance

Storage

Extraction

DrinkingWater

Treatment

Distribution

UseWastewaterCollection

Wastewatertreatment

Septic tank

Reclaimedwater

Wastewaterresiduals

Incinerated

Landfill

Surfacedisposal

Fertilizer/soilconditioner

Raw water

ChemicalsSludge

Rainfall

Irrigation

Water inputs/outputs

Drinking water system

Inputs

Solid wastes

Wastewater system

Contained in this study

Chemicals

Biosolids

Source: Adapted from McGuckin et al, 2013

FIGURE 1 Water and wastewater components of a typical urban water cycle

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on industry-specific emission factors generated from industry-supported studies for regulated or top GHG sectors.

Global warming potential and ownership contribution of GHGs. Six GHGs are required for monitoring at a national scale by the signatory countries to the Kyoto Protocol. Within the urban water cycle, emissions of hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are usually de minimus (typically < 1%) relative to carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The global warming potential of these gases, shown in Table 3, demonstrates the importance of monitoring for CH4 and N2O even when these emissions occur at much lower levels than CO2 (Forster et al, 2007). A summary of the universally accepted scope definitions for emission ownership and contribut-ing sources is provided in Table 4. GHG emissions will accom-pany almost every process in the water cycle because of the heavy reliance on pumping to move water and when higher-energy treatment processes are used. Exceptions to high pumping occur in regions that can take advantage of gravity-fed conveyance

systems to avoid energy input, particularly when additional energy can be created through installation of hydrokinetic in-conduit turbines (e.g., Riverside, Calif.; Portland, Ore.; and Weston, Mass.). Emissions associated with power for pumping or treatment processes are considered scope 1 when onsite fuel combustion is used for power generation and are considered scope 2 when grid electricity is used. Scope 1 direct-process emis-sions of CH4 or N2O occur in wastewater treatment facilities and to a lesser degree during oxidative water treatment processes using ozone generated from air or from regeneration of activated carbon. Such emissions are also associated with water and waste-water sludge–disposal practices. A breakdown of sources and type of GHG emissions from water treatment facility processes is shown in Table 5 and from wastewater treatment facility pro-cesses is shown in Table 6. Many water sector utilities that vol-untarily report emissions focus on scope 1 and 2 sources and omit scope 3 emissions that cover all other indirect sources of emission not covered by scope 2 (McGuckin et al, 2013).

TABLE 1 Regulations that may trigger reporting requirements for the water sector

Country and Agency Regulation Trigger Potential Water Sector Impact

US Environmental Protection Agency

Greenhouse Gas Reporting Program (40 CFR Part 98; 64 FR 56260)

Owners or operators of facilities where aggregate annual GHG emissions are ≥ 25,000 t of CO2e must report to USEPA under the Clean Air Act

Any water facility exceeding the threshold must report as of Sept. 30, 2011. The following USEPA tool can be used to assess whether a facility must report: http://www.epa.gov/climat-echange/emissions/GHG-calculator/index.html. USEPA does not plan to require permits for sources that emit a threshold < 50,000 t until sometime after Apr. 30, 2016.

United States: California Air Resources Board

California GHG Mandatory Reporting Program (95100-95133 Title 17, Califor- nia Code of Regulations)

Reporting threshold of 25,000 t annually of CO2 for most industrial sectors

Water facilities emitting below the threshold must report emissions if they use a cogeneration system that individually has a name-plate-generating capacity ≥ 1MW and emits > 2,500 t CO2/cal-endar year.

United States: California Department of Water Resources Grant Program

California Environmental Quality Act Guideline Amendments (Title 14 of Cali- fornia Code of Regulations)

CEQA applies to governmental action either for direct participation, whole or partial financing of activities, or approval of private activities

Any water project activity subject to CEQA must include quantita-tive accounting for GHG sources to the extent possible as part of the environmental impact report (CEQA Guidelines: Article 1, 2011).

Environment Canada Greenhouse Gas Emissions Reporting Program

Reporting threshold lowered to 50,000 t of CO2e

Any water facility exceeding threshold must report.

European Union European Union Emissions Trading System Directive 2003/87/EC plus amendments of the European Parliament and of the Council

Stationary sources > 25,000 t of CO2e/y and low emissions installations below this trigger level

Section 4, Article 47, allows stationary installations with low emis-sions to submit a simplified monitoring plan in accordance with Article 13. Tier 1 reporting (lowest accuracy requirement) is acceptable for activity data and calculation factors for all sourc-es unless higher accuracy is achievable without additional effort for the operator. Combustion process emissions include boilers, burners, turbines, heaters, furnaces, incinerators, kilns, ovens, dryers, engines, flares, scrubbers, and any other equipment or machinery using fuel exclusive of those for transportation pur-poses. Fuel emission factors were derived from IPCC 2006 GL.

United Kingdom: Environment Agency Department of Energy and Climate Change

Carbon Reduction Commitment Energy Efficiency Scheme

All public and private organizations exceeding 6,000 MW·h/y of electricity must participate

All water companies fall under this scheme, and reporting of annual GHG emissions is required in England and Wales by the water industry economic regulator, Ofwat.

Scotland Climate Change Act 2009 Not specified at local sector level Scottish Water provides GHG reporting on a voluntary basis.

Australia National Greenhouse and Energy Reporting Act

Facilities where aggregate annual GHG emissions are ≥ 25,000 t of CO2e or electricity consumption is > 25,000 MW

Any water facility exceeding the threshold must report.

Japan Kyoto Protocol Target Achievement Plan 2005

Facilities in which aggregate annual GHG emissions are ≥ 3,000 t of CO2e

The Keidanren Voluntary Action Plan specifies GHG reductions to various sectors and covers 35 industries that do not include the water/wastewater sector.

McGuckin et al, 2013

CEQA—California Environmental Quality Act, CO2—carbon dioxide, CO2e—equivalent carbon dioxide, GHG—greenhouse gas, USEPA—US Environmental Protection Agency

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URBAN WATER CYCLE ENERGY DEMAND–MINIMIZATION STRATEGIES

The energy requirement per volume of water, referred to as energy intensity or embedded energy, represents the total amount of operational energy required for use of a given quantity of water in a specific location (Wilkinson, 2000). The energy intensities for potable water cover requirements for pumping, treatment, and distribution. The intensities discussed subsequently would be higher if lifecycle issues and effects of capital construction were also included. Energy intensities of 380–2,800 k·Wh/mil gal have been reported for potable water (GWRC, 2008; NYSERDA, 2008; USEPA, 2008; Elliott et al, 2003) with 85% attributable to pump-ing in systems that are not gravity-fed (EPRI, 2002). These values can be considerably higher in water-scarce and mountainous regions. For example, California requires 9,200 k·Wh/mil gal just for pumping water over the 2,000-ft Tehachapi Mountains (Wolff et al, 2004). Typical energy intensities of 670–4,600 k·Wh/mil gal have been reported for treatment processes at wastewater facili-ties (WEF, 2009; GWRC, 2008; NYSERDA, 2008) with approx-

imately 50% attributable to the aeration needed for the biologi-cal stabilization process. Treatment-process power requirements as high as 6,000 k·Wh/mil gal are needed when membrane bio-reactors are used in place of activated sludge or extended aeration (Crawford & Sandino, 2010). Within major cities in Australia, the pumping energy for wastewater facilities ranged from 16 to 62% of the energy used for treatment, whereas pumping for water facilities ranged from 100 to 1,900% of the energy required for treatment (Kenway et al, 2008). Therefore the greatest opportu-nity for energy minimization for the potable water sector lies in source-selection alternatives and the design and operation of the pumping systems for conveyance and distribution of the water. Energy inefficiency in pumping system design typically occurs as a result of system oversizing for handling peak loading, pipeline scaling, and other performance unknowns (Senon et al, in press). Failure to perform adequate monitoring, maintenance, and replacement of pump equipment is another cause of inefficiencies that occur when operational expenditure improvements do not provide adequate payback in terms of capital expenditures.

TABLE 2 Levels of GHG standards and reporting

Level Entity Examples Key Features Applicability to the Urban Water Cycle

Top Global accounting standard WRI, ISO, ANSI Recognized protocols and certification standard for global, multisector, organizationwide manage-ment and accounting framework. Organizations may use these standards and report to almost any registry.

Framework can be used for any water utility. WRI is the foundational protocol for all orga-nizationwide reporting.

Global voluntary registrations GRI, CDP Registry with global, multisector, organizationwide protocols. Protocols dictate the methodology to be used.

Water utilities may report to these entities. Reports from utilities that have chosen to do so are on each registry’s website.

United Nations IPCC/UNFCCC, Kyoto Protocol CDM and JI

For signatories, multisector, top-down (IPCC) and project-specific (CDM/JI). Methodologies serve as the general foundation for much of the global regulation of GHGs.

IPCC methodology for wastewater and com-bustion. Several CDM and JI projects have focused on the water sector and are avail-able on the UNFCCC website.

Middle National governmental regulatory agency

USEPA Regulatory—focus on top GHG sectors, facility-specific. Methodology tailored to national needs, but equations may have top-down legacy from IPCC.

In certain countries the water sector may be covered.

Regional voluntary registries or standards

TCR, ICLEI/LGOP Voluntary—focus on the top GHG sectors. Method-ology tailored to national, regional, sectorial needs. Efforts are in process for improvement of methodologies to become bottom-up.

The LGOP has gone to great lengths to create a comprehensive methodology for wastewa-ter GHG accounting. Most voluntary report-ing bodies use LGOP.

Region- or sector-specific government agency

DEFRA Regulatory—focus on own sector, facility-specific. Methodology tailored to national and sectorial needs, equations may reflect bottom-up data & research.

Excellent precedents have been set in the United Kingdom for how to tailor a method-ology to the water sector.

Bottom Industry association standards and research papers

WRF, WEF, WERF, GWRC, IWA, UKWIR

Research efforts to understand and model bottom-up data

Wide disparities have been shown between reported data and the top-down equations put forth by IPCC and national regulators. This research may pave the way for more accurate equations and models.

Facility-specific The best single source of data. Some regulatory entities require actual monitoring for top emitters, but not in the water sector.

Actual, measured data is the best means of reporting, but often cost-prohibitive and challenging because of the fugitive nature of many GHG emissions.

McGuckin et al, 2013

ANSI—American National Standards Institute; CDM—Clean Development Mechanism; CDP—Carbon Disclosure Project; DEFRA—Department for Environment, Food, and Rural Affairs; GHG—greenhouse gas; GRI—Global Reporting Initiative; GWRC—Global Water Research Coalition; ICLEI—International Council for Local Environmental Initiatives; IPCC—Intergovernmental Panel on Climate Change; ISO—International Organization for Standardization; IWA—International Water Association; JI—joint implementation; LGOP—Local Government Operations Protocol; TCR—The Climate Registry; UKWIR—UK Water Industry Research; UNFCCC—United Nations Framework Convention on Climate Change; USEPA—US Environmental Protection Agency; WEF—Water Environment Federation; WERF—Water Environment Research Federation; WRF—Water Research Foundation; WRI—World Resources Institute

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Potable water facility energy-reduction strategies. The potable water industry, on an individual facility basis, can achieve addi-tional energy-demand reduction through four key strategies. These strategies, described in the following paragraphs, focus on achieving higher water-use efficiency, selecting lower embedded-energy water sources, optimizing distribution-system energy effi-ciency, and increasing reliance on renewable-energy production.

The first strategy is the implementation of water-use efficiency programs. These programs promote demand-side conservation through consumer education programs, rebates or supply of

water-saving devices for consumers, and tiered rate structures. Programs for supply-side conservation use leak-detection surveys, water audits, and integration of reclaimed water opportunities. Manuals of practice are available that provide methodologies and algorithms for assessing water savings (AWWA, 2009), but they cannot be linked to energy savings without an understanding of the embedded-energy values of the avoided water demand.

The second strategy is the selection of system sources with lower embedded energy. The California Public Utility Commis-sion (CPUC) is investigating the feasibility of calculating the embedded energy in water in order to drive energy efficiency through water conservation programs. Lack of granularity for the treatment input data results in wide variability among func-tional components in retail water and wastewater systems. Although the information is useful for benchmarking, algorithms for computing energy embedded in a unit of water still need to be developed (CPUC Energy Division, 2010). Embedded energy can be dramatically higher for supplies with higher pumping requirements (groundwater and imported water) or treatment requirements (desalination) as shown in Table 7.

The third strategy is to optimize energy efficiency in a distribu-tion system. Energy efficiency of a water network’s distribution system can be estimated from the ratio of the power required to meet the minimum level of service pressure to the total actual power used. A case study within eight zones of a water utility serving a large European city ranged from 31 to 59% (Boulos & Bros, 2010). Pressure reduction achieved in water networks using turbines or pumps as turbines in place of pressure-reducing valves provides a means of simultaneously reducing water and energy loss (Giugni et al, 2009). Distribution-system energy-efficiency strategies must be achieved without introducing unac-ceptable water quality risks or inappropriate pressures. Limiting water age is viewed as a major control parameter in preventing water quality deterioration within a distribution system (USEPA, 2006) whereas pressure zoning is used to achieve regulated minimum operational pressures (Boulos et al, 2006). Proper design of pressure zones will also reduce leaks, breaks, and

TABLE 3 Global-warming potential estimates of GHGs

GHG Global Warming Potential*—(dimensionless)

Carbon dioxide 1

Methane 21–25

Nitrous oxide 298–310

Sulfur hexafluoride† 22,800–23,900

Hydrofluorocarbons† 77–14,800

Perfluorocarbons† 6,500–12,200

Source: Forster et al, 2007

GHG—greenhouse gas

*For a 100-year horizon†Actual value is compound-specific

TABLE 4 Universal scope definitions

Scope Designation

Ownership Level Contributing Sources

1 Direct Fuel combustion

Process emissions

Facility-owned vehicles

HVAC and refrigeration

2 Indirect Purchased electricity or steam for owner use

3 Indirect Production of purchased materials

Employee business travel

Waste disposal

Outsourced activities

Contractor-owned vehicles

Product use

Source: WRI/WBCSD, 2005

HVAC—heating, ventilation, and air-conditioning

TABLE 5 Sources and types of GHG emissions from water treatment facilities*

Sources Scope† GHG‡

Conveyance—pumping

Extraction—pumping

Treatment—coagulation/ flocculation/sedimentation

Treatment—filtration

Treatment—carbon

Treatment—chlorine/ chloramines

Treatment—ultraviolet light

Treatment—lime softening/ recarbonation

Distribution

Power—2 or 1

Facility construction and maintenance—3

CO2 CH4 N2O

Storage Facility construction & maintenance—3

CO2 CH4 N2O

Treatment—ozone Power—2 or 1

Construction and maintenance—3

Ozone generation of N2O—1

CO2 CH4 N2O

Sludge to landfill Waste disposal—3 CH4

Sludge applied to land Waste disposal—3 CH4 N2O

Source: McGuckin et al, 2013

CH4—methane, CO2—carbon dioxide, GHG—greenhouse gas, N2O—nitrous oxide

*Excludes consideration of vehicles†Scope for power will be 2 if electricity is used and 1 if on-site fuel is used.‡CH4 and N2O generation is dependent on fuels combusted.

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pumping costs (NRC, 2006) that contribute to higher GHG emissions. Commercially available energy and water quality management systems (EWQMS) can assist in automating distri-bution-system water storage turnover in order to achieve more energy-efficient pumping strategies (Bunn, 2007). In areas with-out flat tariff rates, however, energy cost savings frequently override energy-minimization strategies.

The fourth strategy is an increased reliance on energy obtained from renewable fuel sources. Onsite implementation of renew-able energy can be purchased and operated directly or obtained through a contract with a third-party provider that owns and manages the equipment. Another alternative is to indirectly obtain renewable energy through the purchase of renewable energy certificates (RECs; USEPA, 2013). When renewable energy is directly installed onsite, careful planning and evalua-tions are needed to maximize the benefits from these systems (Lisk et al, 2012).

Wastewater facility energy-reduction strategies. The wastewater industry, on an individual facility basis, can achieve additional energy-demand reduction through five key strategies. These strat-egies, described in the following paragraphs, focus on minimizing collection system infiltration and inflow, modifying activated sludge aeration systems, optimizing ultraviolet (UV) disinfection systems, capitalizing on combined heat and power (CHP) instal-lation opportunities, and capturing additional latent energy in digested biosolids.

The first strategy relies on detection of structural failures via flow monitoring and physical condition assessment of gravity flow systems, pressure systems, and appurtenances using newer technologies. These include sewer scanner and evaluation tech-nologies, sonar, seismic resurgence testing, acoustic testing, and infrared thermographic investigations in addition to conventional closed-circuit television (Tafuri & Selvakumar, 2002). However, it is important to understand the GHG emissions from production and use of these technologies in order to properly assess the net benefit in GHG reductions.

The second strategy improves oxygen transfer efficiency in acti-vated sludge aeration systems by using off-gas monitoring with mathematical modeling. This is used to signal the diffuser cleaning frequency or when flow equalization is available (Leu et al, 2009).

The third strategy focuses on mitigating the energy require-ments of wastewater UV disinfection systems, which operate at substantially higher doses than drinking water systems. Dose-pacing via intensity-based control or on-line transmittance mon-itoring (Wood et al, 2005) avoids unnecessary energy input. Low-pressure, high-output (LPHO) UV lamps have better germi-cidal efficiency than medium-pressure lamps and for the doses used for wastewater disinfection provide equivalent protection against photoreactivation of total coliforms (Guo et al, 2009). LPHO lamps, however, may be less effective for adenovirus (Lin-den et al, 2007), which could be significant because adenovirus has been demonstrated to pass through secondary treatment with membrane bioreactors (Hirani et al, 2013). This demonstrates the importance of always ensuring that all design and operational considerations for energy savings are still capable of meeting all environmental and public health goals.

The fourth strategy focuses on implementing CHP systems that can use biogas to simultaneously generate electricity and heat with a prime mover that drives the overall system (e.g., reciprocating engine, microturbine, fuel cell). CHP systems were used at 104 wastewater treatment facilities as of June 2011. They were considered technically feasible at 1,351 additional sites and economically attractive (a seven-year payback) at 257–662 of those sites (USEPA, 2011).

TABLE 6 Sources and type of GHG emissions from wastewater treatment facilities*

Scope† Sources GHG‡

Power—2 or 1

Facility construction and maintenance—3

Methane release from sewer—1

Collection system— pumping

CO2 CH4 N2O

Power—2 or 1

Methane from untreated wastewater— 1 facility construction and maintenance—3

Treatment—headwork

Treatment—primary

CO2 CH4 N2O

Power for aeration—2 or 1

Oxygen generation—2 or 1

N2O release during N/dN treatment or effluent discharge—1

Facility construction and maintenance—3

Treatment—activated sludge

CO2 CH4 N2O

Power—2 or 1

N2O release during N/dN treatment—1

Ozone generation of N2O—1

Treatment—filters

Treatment—ozone

CO2 CH4 N2O

Power—2 or 1

Facility construction and maintenance—3

Treatment—chlorine

Treatment—ultraviolet

Treatment—reclaimed potable

Distribution—nonpota-ble reclaimed

CO2 CH4 N2O

Waste disposal—1 (onsite) or 3 (outsourced)

Biosolids§—landfill CH4

Fugitive emissions—1 Biosolids§—incinerated CH4 N2O

Waste disposal as product—3 Biosolids§—fertilizer/soil amendment

Waste disposal—1 (onsite) or 3 (outsourced)

Biosolids§—compost-ing

Fugitive emissions—1 Biosolids§—digester gas capture

CH4 N2O

Biosolids§—combined heat power

Fugitive emissions—1 Biosolids§—dewatering CH4

Biosolids§—anaerobic digestion

Source: McGuckin et al, 2013

CH4—methane, CO2—carbon dioxide, CO2e—equivalent carbon dioxide, GHG—greenhouse gas, N2O—nitrous oxide, N/dN—nitrification/denitrification

*2 if electricity, 1 if onsite fuel†CH4 and N2O generation dependent on fuels used for power‡ Biosolids power for incineration has been omitted on the assumption that it occurs outside facility boundaries.

§Excludes consideration of vehicles

Depending on fuel, CH4 and N2O emissions may also occur that are then translated to CO2e values.

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The fifth strategy of energy recovery from biosolids conven-tionally has been achieved by using the CH4 from aqueous anaerobic digestion of the wastewater treatment–facility sludge alone or in combination with additional substrates such as manure (Crawford & Sandino, 2010). Incineration of digested biosolids for electricity generation is generally a net consumer of rather than a source of energy (Wang et al, 2008), but under suitable conditions can be used to generate a portion of a plant’s annual electricity consumption (Stillwell et al, 2010).

TOOLS FOR ENERGY-RELATED GHG EMISSION MANAGEMENT Benchmarking tools assess utility performance within the context

of organizational peer performance or industry standards to inform operational improvements. Benchmarking tools applicable to the urban water cycle are summarized in Table 8. These tools provide water and wastewater facility energy metrics derived from energy-use models, pumping system operational-efficiency metrics, motor-selection metrics, and water supply portfolio-selection metrics. Energy management tools that provide automated real-time or near real-time control for improved energy efficiency of operations are limited and summarized in Table 9. These systems use demand forecasting and hydraulic modeling to reduce distribution-system water pumping, improve pumping-system efficiencies, or provide real-time relative energy-use data through system submetering. Although energy reductions simultaneously reduce carbon emissions, these tools do not presently use carbon emissions as a control param-eter (Reynolds & Bunn, 2010). There is still a heavy focus on shift-ing operations to use lower electricity tariff periods that offer cost savings but provide no reduction in GHG emissions unless low tariff periods coincide with lower GHG-emitting fuel sources.

MODELING DIRECT GHG EMISSIONS FROM WATER AND WASTEWATER FACILITIES

Water facilities have two processes that generate direct GHG emissions. N2O is released if air and not oxygen is used to gener-

ate ozone for oxidation or disinfection. An emission factor of 0.00011 Kg N20/m3 was derived from work performed at Thames Water Utilities (UKWIR, 2005). Use of air as the feed gas for ozone generation has the additional disadvantage of requiring a specific energy about twice as high as that for pure oxygen because of the lower ozone rate of production at similar power-consumption levels (Gottschalk et al, 2010). As long as high-purity oxygen is purchased and stored as a liquid for ozone generation, onsite N2O emissions will be de minimus. CO2, CH4, and N2O will also be produced when granular activated carbon (GAC) is used for treatment. The emissions occur from the fuel combusted to heat the furnace for the GAC regeneration process. GHG emissions can be calculated when the fuel consumption is directly measurable. In cases in which the direct fuel consumption is confounded by consumption for additional purposes, emitted values can be estimated using a set of equations based on a regen-eration energy of 6,000 Btu/lb GAC and use of natural gas as the fuel source (Huxley et al, 2009).

Additional CO2 emissions must be included for the oxidation of lost carbon. This is calculated by multiplying the tons of lost GAC by the molecular weight ratio of CO2/carbon (44/12).

Modeling is needed to understand direct emissions of CH4 and N2O from wastewater facilities. The protocols and tools associ-ated with different stages of granularity for modeling these emis-sions are summarized in Table 10. Stage A empirical modeling is for municipal-level reporting using methodologies supplied in NGER (2011), LGOP (2010), and IPCC (2006). Stage A model-ing assumes a single-process performance characteristic derived from minimal data and lacks consideration of variations in pro-cess design and operation, thereby falsely restricting variation in direct-process GHG emissions. Stage B and stage C modeling efforts are better attempts to capture these influences on GHG emission estimates.

Stage B modeling uses process simulations that assume steady-state operating conditions and therefore only simulate “average”

TABLE 7 Embedded energy estimates of different sources and treatment processes (excluding distribution)

Source/Treatment Energy Need Energy Variables Values—kW·h/acre ft*

Groundwater Pumping Groundwater depth 175–740

Surface water (imported) Pumping Flow, distance 2,000–3,000 (average)

Surface water (local) Pumping Flow, distance 35–500

Recycled water (irrigation) Pumping Flow, distance 500

Brackish water Pumping Salt concentration 400–1,700

Seawater Pumping Energy recovery devices, power plant colocation 4,500–5,500

Ultraviolet disinfection Lamps Flow, lamp pressure dose, reactor hydraulics 6.5–29†

Ozone disinfection Generator Flow, feed-gas system dose 6.5–52

Micro-/ultra-filtration Pumping Feed pressure 130–325

Reverse osmosis Pumping Feed pressure 163–1,560

Membrane bioreactor Aeration, pumping Pore size, air-transfer efficiency 978–2,440

Sources: Chang et al, 2008; Wilkinson, 2007; NRDC, 2004; EPRI, 2002

*Average number of kilowatt-hours required to pump an acre-foot of water through the system†Case study values for medium pressure lamps.

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plant performance characteristics. Two examples of stage B model-ing tools for wastewater facility GHG emissions are CHEApet (carbon, heat, energy assessment plant evaluation tool; Crawford et al, 2011) and BEAM (biosolids emissions assessment model; CCME, 2009). CHEApet is a steady-state, whole-plant simulator that uses solids, nitrogen, and chemical oxygen demand mass-balance equations that follow several widely accepted kinetic models and integrate them with calorific, thermal, and electrical modules to estimate overall plant energy usage, energy-associated GHG emissions, and direct N2O and CH4 emissions from process models. CHEApet also allows the integration of higher stage A protocol methodologies (LGOP, 2010) for estimating direct process emissions of N2O and is one of the only tools to allow a choice in specificity of GHG emission estimations for selected emission sources within the treatment facility. The estimation of emissions from biosolids is considerably weaker and relies extensively on the stage A guidelines in the IPCC (2006). A stage B estimation of GHG emissions from biosolids processing is available in BEAM (CCME, 2009). The algorithms used in BEAM were obtained from an extensive literature review of biosolids practices and nine Cana-dian jurisdiction facilities. Integration of CH4 emission estimations from anaerobic portions of sewer conveyance and headworks still needs further development.

Stage C modeling can simulate the effects of real-time process changes through use of mechanistic process models with dynamic simulators. Some wastewater processes are not at steady state and are more accurately predicted with dynamic stage C models. These processes include nitrification/denitrification and anaerobic digestion of biosolids for energy recovery. Stage C modeling of wastewater facilities is being developed and released by com-mercial vendors of dynamic process simulators (e.g., BioWin, GPS-X, and Aquifas). Incorporation of N2O within the Petersen matrix of these biological models and use of additional biological process model equations are being developed. Noncommercial development using shareware such as MATLAB offers another avenue of simulator development. Stage C modeling of energy recovery via solids-treatment alternatives is available with LCAMER (Life Cycle Assessment Manager for Energy Recovery; WERF, 2006). LCAMER applies systems-level life-cycle assess-ment modeling of solids-treatment energy-recovery technologies and evaluates the impact of these sludge-treatment alternatives on overall plant operations. LCAMER does not cover all aspects involved with biosolids handling, processing, and disposal, and in this respect it is less comprehensive than BEAM. LCAMER is more comprehensive than BEAM in providing systems-level assessment of optimal energy-recovery options with respect to

TABLE 8 Tools for energy benchmarking

Name of Tool Application Description

USEPA Energy Star Water and wastewater Ordinary least-squares regression across a filtered survey data set with EUI (source energy use per gallon of treatment per day) as the dependent variable

Water Research Foundation Energy Benchmarking

Water and wastewater Provided survey data analysis to the USEPA Energy Star benchmarking tool for wastewater facili-ties and contributed toward testing of the final model in coordination with NYSERDA and USEPA

NYSERDA Water and wastewater New York State energy use survey data aggregated by facility size for water and wastewater facilities

DOE PSAT Pumps Assesses efficiency of pumping system operations using achievable pump-performance data from Hydraulic Institute standards and motor performance data to calculate potential energy savings

DOE MotorMaster Version +4.0 and Ver-sion MotorMaster+ International

Motors Motor selection management tool based on motor efficiency standards. Internal version includes 50 Hz metric or IEC motors, multiple language capability, multiple currency calculations, and regional minimum full-load efficiency standards and country-specific motor repair and installation cost defaults.

Water to Air Model Water supply portfolio Emission-activity factor Excel spreadsheet calculations for input portfolio of energy mix alterna-tives and default or actual energy use for each supply portfolio option

National Water and Wastewater Bench-Marking Initiative

Water and wastewater 50 performance measures for Canadian facilities (www.nationalbenchmarking.ca)

DOE—Department of Energy, IEC—International Electrotechnical Commission, NYSERDA—New York State Energy Research and Development Authority, PSAT—pump system assessment tool, USEPA—US Environmental Protection Agency

TABLE 9 Tools for energy management

Name of Tool Application Description

Derceto Aquadapt Water-pumping and storage-scheduling interface with SCADA and telemetry systems

Uses live data collection from SCADA to predict water consumption and opti-mize energy time of use, peak demand reduction, pump efficiency, reduc-tion in water travel distance, source optimization

Innovyze IW Live for InfoWater Water distribution system control through hydrau-lic modeling in the control room inclusive of energy reduction schemes

Real-time water supply hydraulic modeling

Optima™ Energy Management Entire agency within United Kingdom Energy consumption automatic monitoring and targeting

SCADA—supervisory control and data acquisition

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life-cycle cost. BEAM lacks adequate information on N2O emis-sions during sludge handling and LCAMER provides no informa-tion on N2O emissions in evaluating energy recovery alternatives. A descriptive summary of these models, associated protocols/tools, and application sources is provided in Table 10.

TOOLS FOR LIFE-CYCLE CARBON ASSESSMENTScope 3 emissions include indirect emissions not covered in scope

2 that occur outside the boundary of the utility for the provision of needed goods and services. They occur during extraction and pro-duction of purchased materials and fuels, transport-related activities in vehicles not owned or controlled by the reporting entity, transmis-sion and distribution losses of electricity-related activities, out-sourced activities, and waste disposal. Scope 3 category reporting is less emphasized in government enterprise reporting than it is in commercial product-level reporting. For this reason, many urban water cycle agencies that voluntarily report carbon emissions focus on scopes 1 and 2 categories (McGuckin et al, 2013). Scope 3 sources, when included, can be more difficult to accurately assess because of a dearth of appropriate emission factors for water facil-ity construction or manufacture of water utility supplies. Table 11 provides an overview of protocols and tools for estimating facility-embodied carbon as well as life-cycle assessment of products and systems that support the engineered urban water cycle.

CONCLUSIONS Comprehensive GHG emissions accounting and control meth-

odologies for all segments of the urban water cycle are not fully developed. Unlike the oil and natural gas industry, which has a continually updated compendium of GHG-emission estimation methodologies (Shires et al, 2009) that incorporate peer reviews and updates on emission factors and methodologies, the water industry is still developing more accurate modeling of scope 1 process emission factors, elucidating the impact of scope 2 energy-minimization strategies (i.e., GHG emission reductions) on existing operational strategies for energy cost minimization (e.g., EWQMS) and incorporating the impact of scope 3 embod-ied carbon on capital improvement projects and chemicals/supply-chain products on routine operational emissions. Much of this information remains site-specific and dispersed because of the absence of regulatory reporting requirements or economic incentives to drive industrywide development of methodologies and emission factors.

In the United States, the California Air Resources Board (CARB) has developed a scoping plan consisting of 18 GHG emission-reduction strategies in support of the California Global Warming Solutions Act (AB 32) of 2006 that requires the state to meet GHG emission-reduction targets by 2020 and 2050. Mea-sure 17 focuses on GHG emission reductions from water through

TABLE 10 Stages of granularity for modeling GHG emissions from wastewater processes

Stage of Granularity and Model

Associated Protocol/Tool Application Sources Description

Stage A: plant empirical data

LGOP, IPCC, NGER, UKWIR workbook

Biotreatment, sludge digestion, sludge reuse, chemical usage, power consump-tion, biogas usage

Compiled literature of emission factor estimates for use in emis-sion factor–activity level calculations.

Stage B: plant static model Bridle model Biotreatment, sludge digestion, sludge reuse, chemical usage, power consump-tion, biogas usage

Stoichiometric equations described in Snip, 2010. Calculates CO2 of biotreatment, biogas, and chemicals, N2O of biotreat-ment, CH4 of biogas, calculates aeration power and converts this plus additional power use to CO2 emissions, calculates power generation credits from sludge.

Stage B: plant static simulator CHEApet Influent pumping, 1°, 2°, filtration, ultravio-let disinfection, effluent pumping, sludge pumping, sludge thickening, sludge sta-bilization, sludge dewatering, side stream treatment

Steady-state simulation model, IWA ASMN model (Hiatt and Grady, 2008), IWA ADM1 model (Batstone et al, 2002) inte-grated with mass/calorific balance, electrical consumption, thermal consumption/capture to provide carbon footprint.

Stage C: plant dynamic simula- tor (pending next revision)

Biowin, GPS-X, WEST STOAT®

Simba, Aquifas

Same processes as CHEApet minus ultra-violet disinfection

Biokinetic dynamic process models derived from IWA ASMN2d, ADM1 models. Needs extension of state variables to include N2O. Aquifas has modified IWA ASM2d biokinetic model that includes four-step nitrification and denitrification processes (Sen and Lodhi, 2010).

Stage C: plant dynamic simulator coupled with rising main sewer benchmark simulator (in progress)

IWA Task Group GHG Subgroup

Same processes as CHEApet plus collection system minus ultraviolet disinfection

BSM2 modeling platform with ASMN two-step nitrification model, ASM1, ADM1, and model of Guisasola et al (2009) for CH4 in mains.

Stage B: biosolids processing BEAM Storage, conditioning, and thickening; aer-obic and anaerobic digestion; dewater-ing, drying, alkaline stabilization, composting, landfilling, combustion, land application, transportation

Extension of IPCC guidelines using data from published literature and Kyoto Protocol Clean Development Mechanism protocols (UNFCCC/CCNUCC, 2008). Inclusion of fugitive emission estimates together with scope 1, 2, and 3 processing requirements enables assessment of solids-handling alternatives with lowest GHG emissions.

Source: McGuckin et al, 2013

ADM—Anaerobic Digestion Model; ASM—Activated Sludge Model; BEAM—Biosolids Emissions Assessment Model; BSM—Benchmark Simulation Model; CH4—methane; CHEApet—carbon, heat, energy assessment plant evaluation tool; CO2—carbon dioxide; GHG—greenhouse gas; IPCC—Intergovernmental Panel on Climate Change; IWA—International Water Association; LGOP—Local Government Operations Protocol; N2O—nitrous oxide; NGER—National Greenhouse and Energy Reporting; UKWIR—UK Water Industry Research; WEST—Water-Energy Sustainability Tool

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efficiency programs and use of cleaner energy sources to move and treat water. Local-government reduction efforts rely on CARB’s published Local Government Operations Protocol (LGOP—developed and adopted in partnership with ICLEI-Local Governments for Sustainability, The Climate Registry, and the California Climate Action Registry) for the detailed methodolo-gies and emission factor to be used for GHG inventories. The LGOP is a top-down government accounting system that still lacks accurate methodologies for some urban water cycle GHG emission sources. It could, however, be used as a foundational interface with water industry–specific methodologies under development and as a repository of more accurate emission fac-tors as they are developed within the water and wastewater sec-tors that support the urban water cycle.

This overview presents an initial snapshot of the protocols, methodologies, and tools available or under development that are appropriate for monitoring, reporting, and minimizing GHG emissions within the urban water cycle. In the absence of eco-nomic and/or regulatory drivers that promote GHG reductions within the urban water cycle, the water sector focus remains on more readily implementable energy cost–saving strategies rather than on GHG emission reduction–focused strategies. Tackling GHG reductions through energy minimization is more difficult to achieve because of the need to congruently optimize for water quality, operational needs, and asset management. Achieving GHG reductions through modification of directly emitting pro-cesses remains dependent on implementation of newly developed process-modeling tools that will provide more accurate GHG emission factor estimates.

ACKNOWLEDGMENTThis article has been made possible through funding from

the New York State Energy Research and Development Author-ity (NYSERDA), Global Water Research Coalition (GWRC), and the Water Research Foundation. The information con-tained here is based on intellectual property that is jointly owned by MWH Americas Inc., NYSERDA, GWRC, and the Water Research Foundation. NYSERDA, GWRC, the Water Research Foundation, and MWH Americas Inc. retain their

rights to publish or produce the jointly owned intellectual property in part or in its entirety.

ABOUT THE AUTHORSJoan Oppenheimer is principal scientist and vice-president at MWH, 618 Michilinda Ave., Ste. 200, Arcadia, CA 91107 USA; joan.oppenheimer@mwhglobal.com. She has 33 years of experience in water quality assess-ments and the environmental impacts of treatment solutions. Her degrees are a master of science in public health from the Univer-

sity of North Carolina and a bachelor of arts from Brandeis University. Mohammad Badruzzaman is supervising engineer, Robyn McGuckin is director of clean energy, and Joseph G. Jacangelo is director of research at MWH.

PEER REVIEWDate of submission: 06/21/13Date of acceptance: 11/18/13

REFERENCESAWWA, 2009 (3rd ed.). Manual of Water Supply Practices. M36 Water Audits and

Loss Control Programs. AWWA, Denver.

Batstone, D.J.; Keller, J.; Angelidaki, I.; Kalyuzhnyzi, S.V.; Pavvlostathis, S.G.; Rozzi, A.; Sanders, W.T.M.; Seigrist, H.; & Vavilin, V.A., 2002. The IWA Anaerobic Digestion Model No. 1 (ADM1). Water Science & Technology, 45:10:65.

Boulos, P. & Bros, C., 2010. Assessing the Carbon Footprint of Water Supply and Distribution Systems. Journal AWWA, 102:110:47.

Boulos, P.F.; Lansey, K.; and Karney, B.W., 2006 (2nd ed.). Comprehensive Water Distribution Systems Analysis Handbook for Engineers and Planners. MWH Soft Press, Broomfield, Colo.

Bunn, S., 2007. Greenhouse Gas Reduction as an Additional Benefit of Optimal Pump Scheduling for Water Utilities. CCWI2007 and SUWM2007 Conference, De Montfort University, Leicester, U.K.

CCME (Canadian Council of Ministers of the Environment), 2009. Biosolids Emissions Assessment Model: User Guide. www.ccme.ca/assets/pdf/beam_user_guide_1430.pdf (accessed August 2013).

TABLE 11 Tools for life-cycle carbon assessment

Name of Tool Application Description

UKWIR Embodied & Whole Life Carbon Whole agency within United Kingdom Guidelines for independent tool development. Specific to GHG accounting, not applicable to the other environmental accounting aspects of full LCAs.

WEST (Level 1) Water supply, treatment, and distribution life-cycle impacts of source alternatives

Hybrid of process-based LCA to assess environmental effects of system construc-tion and operation to obtain process-specific results. Economic input–output anal-ysis-based LCA to determine effects of material acquisition, transformation, and production.

SimaPro Products and systems Life-cycle analysis of products and systems using parameters and Monte Carlo simulations that can be integrated with the Ecoinvent database for GHG emission assessment, product eco-design, environmental impact assessment, environ-mental reporting, and determination of key performance indicators.

GaBi Products and systems Life-cycle costing, greenhouse gas accounting, energy benchmarking and efficien-cy, life-cycle engineering, and life-cycle sustainability assessment.

GHG—greenhouse gas, LCA—life-cycle assessment, UKWIR—UK Water Industry Research, WEST—Water-Energy Sustainability Tool

Oppenheimer et al | http://dx.doi.org/10.5942/jawwa.2014.106.0017Peer-Reviewed

E96

2014 © American Water Works AssociationJOURNAL AWWA FEBRUARY 2014 | 106:2

Chang, Y.J.; Reardon, D.J.; Kwan, P.; Boyd, G.; Brant, J.; Rakness, K.W.; and Furukawa, D., 2008. Evaluation of Dynamic Energy Consumption of Advanced Water and Wastewater Treatment Technologies. Awwa Research Foundation & AWWA, Denver.

Copeland, C., 2010. Clean Water Act: A Summary of the Law. Congressional Research Service, Washington. www.oakparkusd.org/cms/lib5/CA01000794/Centricity/Domain/338/clean%20water%20act%20summary.pdf (accessed August 2013).

CPUC (California Public Utilities Commission) Energy Division, 2010. Embedded Energy in Water Studies, Study 2: Water Agency and Function Component Study and Embedded Energy-Water Load Profiles. ftp://ftp.cpuc.ca.gov/gopher-data/energy%20efficiency/Water%20Studies%202/Study%202%20-%20FINAL.pdf (accessed August 2013).

Crawford, G.; Johnson, T.D.; Johnson, B.R.; Krause, T.; & Wilner, H., 2011. CHEApet Users Manual. Water Environment Research Foundation, Alexandria, Va. http://cheapet.werf.org/documentation/OWSO4RO7c%20web.pdf (accessed August 2013).

Crawford, G. & Sandino, J., 2010. Energy Efficiency in Wastewater Treatment in North America: A Compendium of Best Practices and Case Studies of Novel Approaches. Water Environment Research Foundation. IWA Publishing, London, U.K.

Daigger, G.T., 2009. Evolving Urban Water and Residuals Management Paradigms: Water Reclamation and Reuse, Decentralization, and Resource Recovery. Water Environment Research, 81:8:809. http://dx.doi.org/10.2175/106143009X425898.

Elliott, T.; Zeier, B.; Xagoraraki, I.; & Harrington, G., 2003. Energy Use at Wisconsin’s Drinking Water Facilities. Energy Center of Wisconsin, Madison. www.ecw.org/prod/222-1.pdf (accessed August 2013).

EPRI (Electric Power Research Institute), 2002. Water and Sustainability (Volume 4): U.S. Electricity Consumption for Water Supply and Treatment—The Next Half Century. Technical report 1006787. EPRI, Palo Alto, Calif.

Forster, P.; Ramaswamy, V.; Artaxo, P.; Bernstsen, T.; Betts, R.; Fahey, D.W.; Haywood, J.; Lean, J.; Lowe, D.C.; Myhre, G.; Nganga, J.; Prinn, R.; Raga, G.; Schulz, M.; & Van Dorland, R., 2007. Changes in Atmospheric Constituents and in Radiative Forcing. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, (S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, & H.L. Miller, editors). Cambridge University Press, Cambridge, U.K. www.ipcc-wg1.unibe.ch/publications/wg1-ar4/ar4-wg1-chapter2.pdf (accessed August 2013).

GAO (United States Government Accounting Office), 2011. Energy-Water Nexus: Amount of Energy Needed to Supply, Use, and Treat Water Is Location-Specific and Can Be Reduced by Certain Technologies and Approaches. Report to the Ranking Member, Committee on Science, Space, and Technology, House of Representatives, Washington. www.gao.gov/new.items/d11225.pdf (accessed August 2013).

Giugni, M.; Fontana, N.; & Portolano, D., 2009. Energy Saving Policy in Water Distribution Networks. International Conference on Renewable Energies and Power Quality, Valencia, Spain. www.icrepq.com/ICREPQ'09/487-giugni.pdf (accessed August 2013).

Gottschalk, C.; Libra, J.A.; & Saupe, A., 2010 (2nd ed.). Ozonation of Water and Waste Water: A Practical Guide to Understanding Ozone and its Applications. Wiley-VCH, Weinheim, Germany.

Guisasola, A.; Sharma, K.R.; Keller, J.; and Yuan, Z., 2009. Development of a Model for Assessing Methane Formation in Rising Main Sewers. Water Research, 43:11:2874.

Guo, M.; Hu, H.; Bolton, J.R.; & Gamal El-Din, M., 2009. Comparison of Low- and Medium-pressure Ultraviolet Lamps: Photoreactivation of Escerichia coli and Total Coliforms in Secondary Effluents of Municipal Wastewater Treatment Plants. Water Research, 43:3:815. http://dx.doi.org/10.1016/ j.watres.2008.11.028.

GWRC (Global Water Research Coalition), 2008. Water and Energy: Report of the GWRC Research Strategy Workshop. GWRC, London, U.K. www.iwahq.org/contentsuite/upload/iwa/Document/GWRC_Water_and_Energy_workshop_report.pdf (accessed August 2013).

Hiatt, W.C. & Grady Jr., L., 2008. An Updated Process Model for Carbon Oxidation, Nitrification and Denitrification. Water Environment Research, 80:11:2145.

Hirani, Z.M.; Bukhari, Z.; Oppenheimer, J.; Jjemba, P.; LeChevallier, M.W.; & Jacangelo, J.G., 2013. Characterization of Effluent Water Qualities from Satellite Membrane Bioreactor Facilities. Water Research, 47:14:5065. www.sciencedirect.com/science/article/pii/S0043135413004788. (accessed September 2013).

Huxley, D.E.; Bellamy, W.D.; Sathyanarayan, P.; Ridens, M.; & Mack, J., 2009. Greenhouse Gas Emission Inventory and Management Strategy Guidelines for Water Utilities. Water Research Foundation, Denver.

IPPC (Intergovernmental Panel on Climate Change), 2006. Guidelines for National Greenhouse Gas Inventories. Institute for Global Environmental Strategies, Arlington, Va.

Iranpouor, R.; Cox, H.H.J.; Kearney, R.J.; Clark, J.H.; Pincince, A.B.; & Daigger, G.T., 2004. Review of Regulations for Biosolids Land Application in U.S. and European Union. Journal of Residuals Science & Technology, 1:4:209.

Kenway, S.J.; Priestley, A.; Cook. S.; Seo, S.; Inman, M.; Gregory, A.; & Hall, M., 2008. Energy Use in the Provision and Consumption of Urban Water in Australia and New Zealand. Commonwealth Scientific and Industrial Research Organisation, Victoria, Australia; & Water Services Association of Australia, Melbourne, Australia. www.clw.csiro.au/publications/waterforahealthycountry/2008/wfhc-urban-water-energy.pdf (accessed August 2013).

Leu, S.Y.; Rosso, D.; Larson, L.E.; & Stenstrom, M.K., 2009. Real-Time Aeration Efficiency Monitoring in the Activated Sludge Process and Methods to Reduce Energy Consumption and Operating Costs. Water Environment Research, 81:12:2471. http://dx.doi.org/10.2175/106143009X425906.

LGOP (Local Government Operations Protocol), 2010. Local Government Operations Protocol for the Quantification and Reporting of Greenhouse Gas Emissions Inventories, Version 1.1. California Air Resources Board, Sacramento, Calif.; California Climate Action Registry, Los Angeles, Calif.; ICLEI-Local Governments for Sustainability, Oakland, Calif.; & The Climate Registry, Los Angeles, Calif. www.arb.ca.gov/cc/protocols/localgov/pubs/lgo_protocol_v1_1_2010-05-03.pdf (accessed August 2013).

Linden, K.G.; Thurston, J.; Schaefer, R.; & Malley Jr., J.P., 2007. Enhanced UV Inactivation of Adenoviruses under Polychromatic UV Lamps. Applied and Environmental Microbiology, 73:23:7571. http://dx.doi.org/10.1128/AEM.01587-07.

Lisk, B.; Greenberg, E.; & Bloetscher, F., 2012. Implementing Renewable Energy at Water Utilities. Water Research Foundation, Denver.

Marsalek, J.; Jiménez-Cisneros, B.E.; Malmquist, P.-A.; Karamouz, M.; Goldenfum, J.; & Chocat, B., 2006. Urban Water Cycle Processes and Interactions. International Hydrological Programme of the United Nations Educational, Scientific and Cultural Organization, Paris, France. www.bvsde.paho.org/bvsacd/cd63/149460E.pdf (accessed August 2013).

McGuckin, R.; Oppenheimer, J.; Badruzzaman, M.; Contreras, A.; & Jacangelo, J., 2013. Toolbox for Water Utility Energy and Greenhouse Gas Emission Management. Water Research Foundation, Denver.

NGER (National Greenhouse and Energy Reporting), 2011. National Greenhouse and Energy Reporting System Measurement: Technical Guidelines for the Estimation of Greenhouse Gas Emissions by Facilities in Australia. Australian Government Department of Climate Change and Energy Efficiency, Canberra, Australia. www.climatechange.gov.au/climate-change/greenhouse-gas-measurement-and-reporting/company-emissions-measurement/technical/national-greenhouse-and-energy-reporting-measurement-technical-guidelines%E2%80%942011 (accessed August 2013).

Oppenheimer et al | http://dx.doi.org/10.5942/jawwa.2014.106.0017Peer-Reviewed

E97

2014 © American Water Works AssociationJOURNAL AWWA FEBRUARY 2014 | 106:2

NRC (National Research Council) Committee on Public Water Supply Distribution Systems, 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. National Academies Press, Washington.

NRDC (Natural Resources Defense Council) and Pacific Institute, 2004. Energy Down the Drain: The Hidden Costs of California’s Water Supply. Oakland, Calif. www.nrdc.org/water//conservation/edrain/edrain.pdf (accessed August 2013).

NYSERDA (New York State Energy Research and Development Authority), 2008. Statewide Assessment of Energy Use by the Municipal Water and Wastewater Sector. NYSERDA, Albany, N.Y.

Pataki, D.E; Carreiro, M.M.; Cherrier, J.; Grulke, N.E.; Jennings, V.; Pincetl, S.; Pouyat, R.V.; Whitlow, T.H.; & Zipperer, W.C., 2011. Coupling Biogeochemical Cycles in Urban Environments: Ecosystem Services, Green Solutions, and Misconceptions. Frontiers in Ecology and the Environment, 9:1: 27. http://dx.doi.org/10.1890/090220.

Pontius, F., 1990. Complying With the New Drinking Water Quality Regulations. Journal AWWA, 82:2:32.

Pontius, F., 2003 (editor). Drinking Water Regulation and Health. John Wiley & Sons Inc., New York. http://dx.doi.org/10.1002/0471721999.

Prescott, C., 2009. Carbon Accounting in the United Kingdom Water Sector: A Review. Water Science and Technology, 60:10: 2721. http://dx.doi.org/10.2166/wst.2009.708.

Reynolds, L.K. & Bunn, S., 2010. Improving Energy Efficiency of Pumping Systems Through Real-Time Scheduling Systems. Integrating Water Systems (J. Boxall & C Maksimovic’, editors), Taylor & Francis Group, London.

Roberson, J.A., 2011. What’s Next After 40 Years of Drinking Water Regulations? Environmental Science and Technology, 45:1:154. http://dx.doi.org/10.1021/es101410v.

Sen, D. & Lodhi, A., 2010. Applying the Operations Version of the Aquifas + Model to Simultaneously Control Effluent Quanlity, Greenhouse Gas (GHG) and Nitric Oxide Emissions and Energy Consumption in Conventional and Advanced Wastewater Treatment Digestion. Aquifas Development Team, Mountain View, Calif.

Senon, C.; Badruzzaman, M.; Contreras, A.; Adidjaja, J.; Allen, S.M.; & Jacangelo, J.G., in press. Drinking Water Pump Station Design and Operation for Energy Efficiency. Water Research Foundation, Denver.

Shires, T.; Loughran, C.J.; Jones, S.; & Hopkins, E., 2009. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Natural Gas Industry. American Petroleum Institute, Washington.

Snip, L., 2010. Quantifying the Greenhouse Gas Emission of Wastewater Treatment Plants. Master’s thesis, Wageningen University, the Netherlands. http://modeleau.fsg.ulaval.ca/fileadmin/modeleau/documents/Publications/MSc_s/sniplaura_msc.pdf (accessed August 2013).

Solomon, S.; Plattner, G.-K.; Knutti, R.; & Friedlingstein, P., 2007. Irreversible Climate Change Due to Carbon Dioxide Emissions. Proceedings of the National Academy of Sciences of the United States of America, 106:6:1704. http://dx.doi.org/10.1073/pnas.0812721106.

Stillwell, A.S.; Hoppock, D.C.; & Webber, M.E., 2010. Energy Recovery From Wastewater Treatment Plants in the United States: A Case Study of the Energy-Water Nexus. Sustainability, 2:4:945. http://dx.doi.org/10.3390/su2040945.

Tafuri, A.N. & Selvakumar, A., 2002. Wastewater Collection System Infrastructure Research Needs in the USA. Urban Water, 4:1:21. http://dx.doi.org/10.1016/S1462-0758(01)00070-X.

UKWIR (UK Water Industry Research), 2005. Workbook for Quantifying Greenhouse Gas Emissions. Superseded by UKWIR, 2007/2008. Carbon Accounting in the UK Water Industry: Methodology for Estimating Operational Emissions. UKWIR, London, UK.

UNFCCC/CCNUCC (United Nations Framework Convention on Climate Change/La Convention-Cadre des Nations Unies sur les Changements Climatiques) 2008. Kyoto Protocol Clean Development Mechanism. http://unfccc.int/kyoto_protocol/mechanism/clean_development_mechanism/items/2718.php (accessed August 2013).

USEPA (US Environmental Protection Agency), 2013. Going Green: Renewable Energy Options for Water Utilities. USEPA, Washington. http://water.epa.gov/infrastructure/sustain/goinggreen.cfm (accessed Sept. 30, 2013).

USEPA, 2012. Electronic Greenhouse Gas Reporting Tool: e-GGRT Training Webinar on Reporting GHG Data for Subpart HH. USEPA Greenhouse Gas Reporting Program, Washington. www.epa.gov/ghgreporting/documents/pdf/2012/training/Subpart-HH_e-ggrt.pdf (accessed August 2013).

USEPA, 2011. Opportunities for Combined Heat and Power at Wastewater Treatment Facilities: Market Analysis and Lessons from the Field. USEPA Combined Heat and Power Partnership, Washington. www.epa.gov/chp/documents/wwtf_opportunities.pdf (accessed August 2013).

USEPA, 2008. Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities. USEPA Office of Water, Washington, & Global Environment and Technology Foundation, Arlington, Va. www.epa.gov/owm/waterinfrastructure/pdfs/guidebook_si_energymanagement.pdf (accessed August 2013).

USEPA, 2006. Total Coliform Rule (TCR) and Distribution System Issue Papers Overview. www.epa.gov/ogwdw/disinfection/tcr/pdfs/issuepaper_tcr_overview.pdf (accessed August 2013).

Voinov, A. & Cardwell, H., 2009. The Energy-Water Nexus: Why Should We Care? Journal of Contemporary Water Research & Education, 143:1:17. http://dx.doi.org/10.1111/j.1936-704X.2009.00061.x.

Wang, H.L.; Brown, S.L.; Magesan, G.N.; Slade, A.H.; Quintern, M.; Clinton, P.W.; & Payn, T.W., 2008. Technological Options for the Management of Biosolids. Environmental Science and Pollution Research, 15:4:308. http://dx.doi.org/10.1007/s11356-008-0012-5.

WEF (Water Environment Federation), 2009. Energy Conservation in Water and Wastewater Treatment Facilities. Manual of Practice No. 32. WEF Press, Alexandria, Va.

WERF (Water Environment Research Federation), 2006. An Assessment Tool for Managing Cost-Effective Energy Recovery from Anaerobically Digested Wastewater Solids. Water Environment Research Federation, Alexandria, Va.

Wilkinson, R.C., 2007. Analysis of the Energy Intensity of Water Supplies for West Basin Municipal Water District. West Basin Municipal Water District, Carson, Calif. www.westbasin.org/files/general-pdfs/Energy--UCSB-energy-study.pdf (accessed August 2013).

Wilkinson, R.C., 2000. Methodology for Analysis of the Energy Intensity of California’s Water Systems, and an Assessment of Multiple Potential Benefits Through Integrated Water-Energy Efficiency Measures. Exploratory research project, Ernest Orlando Lawrence Berkeley Laboratory, California Institute for Energy Efficiency, University of California, Santa Barbara.

Wolff, G.; Gaur, S.; & Winslow, M., 2004. User Manual for the Pacific Institute Water to Air Models. The Pacific Institute, Oakland, Calif. www.pacinst.org/publication/water-to-air-models/ (accessed August 2013).

Wood, P.; Hunter, G.; & Kobylinski, E., 2005. To PLC or Not to PLC UV Systems—Alternatives for UV System Control. Proceedings of the Water Environment Federation, Disinfection 2005, Phoenix, Ariz. http://dx.doi.org/10.2175/193864705783978456.

WRI (World Resources Institute)/WBCSD (World Business Council for Sustainable Development, 2005. Greenhouse Gas Protocol. WRI, Washington; WBCSD, Geneva. www.ghgprotocol.org/standards/ project-protocol (accessed August 2013).