iiICERIE 2013

ICERIE 2013

11 -13 January 2013

Proceedings

Edited by

Prof. Dr. Mushtaq Ahmed

Dr. Md. Abu Hayat Mithu

Dr. Abu Yousuf

Dr. Md. Shofiqul Islam

School of Applied Sciences & Technology

Shahjalal University of Science & Technology, Sylhet, Bangladesh

Paper # ID NO: ICERIE-ARC-118

Paper Title: Managing Water Demand through Water Conservation and Recycling Techniques

for Residential Buildings in Dhaka: Challenges and Potentials

Author Name: MD. NAWROSE FATEMI

Sub: Acceptance of abstract for submission as a full paper in ICERIE2013, Sylhet

Dear Author,

Thank you very much for your contribution to the success of the forthcoming ICERIE 2013, Sylhet to

be held during 11-13 January 2013, organized by the School of Applied Sciences & Technology,

Shahjalal University of Science & Technology, Sylhet, Bangladesh.

It is our great pleasure to inform you that the above abstract has been reviewed and accepted for

submission as a full paper in the conference. The final decision will be informed after reviewing the full

paper.

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2012 to icerie2013@gmail.com & cc to icerie2013@sust.edu. Please take a look at the attached

author guidelines before you submit the full paper.

Please remember the Paper No. and mention it whenever you communicate with us.

Looking forward to meeting you at SUST, Sylhet in January 2013.

Thanking you.

Dr. Md. Mozammel Hoque

Associate Professor & Head, Dept of FET &

Member Secretary, ICERIE 2013

Shahjalal University of Science & Technology

Sylhet-3114, Bangladesh

Phone: 01715 492961

Email: icerie2013@gmail.com & icerie2013@sust.edu.

108 | F a t e m i , M . N . , I C E R I E 2 0 1 3

Proceedings of the

International Conference on Engineering Research, Innovation and Education 2013

ICERIE 2013, 11 ̶ 13 January, SUST, Sylhet, Bangladesh

Managing Water Demand through Water Conservation and Recycling

Techniques for Residential Buildings in Dhaka: Challenges and

Potentials

Md. Nawrose Fatemi* Department of Architecture, University of Asia Pacific (UAP), Dhaka

Keywords:

Domestic Water Use

Residential Plots

Water Conservation

Rain Water Harvesting

Wastewater Treatment

Abstract: In Dhaka, the demand of water has increased rapidly with ever growing

population, rise in living standards, rapid urbanization and industrialization. The recent

water supply requirement for the city is about 2250 million liter per day (MLD) against

a capacity of supplying 2088 MLD and an estimated water demand of 4990 MLD by

2030. So, it is evident that in coming decades, megacity like Dhaka will have to face

acute water crisis. To deal with this problem, water conservation will be an efficient

solution for the City. Conserving water helps to ensure that this important resource will

be available for many generations to come. A few techniques and devices are currently

on hand to help conserve water, such as Rain Water Harvesting (RWH), Decentralized

Wastewater Treatment System (DEWATS), installation of water efficient fixtures and

appliances, and other similar methods. The objective of this paper is to evaluate the

potentials of these water conservation and recycling techniques for residential

buildings in Dhaka. This paper also outlines the process of incorporating these

techniques in dense urban fabric with special emphasis on typical residential plots

where the FAR (Floor Area Ratio) rules are being or will be applied.

1. INTRODUCTION

Water is an essential part of survival lives. The UN Human Rights Declaration (2002) states that the human right to

water entitles everyone to sufficient, safe, acceptable, physically accessible and affordable water for personal and

domestic uses. The reflection of this declaration is seen in the 'National Policy for Safe Water Supply and Sanitation'

(1998) of Bangladesh. It states: ‘it is necessary to expand and improve the water supply and sanitation services in

order to satisfy the basic needs of the people’. And according to National Water Policy of Bangladesh (1999),

availability of safe and affordable drinking water supplies through various means, including rainwater harvesting

and conservation should be facilitated. In Dhaka, the demand of water is increasing rapidly keeping pace with

growth of population and rise of urbanization and industrialization. The recent water supply requirement for the City

is about 2250 million liter per day (MLD) against a capacity of supplying 2088 MLD and an estimated water

demand of 4990 MLD by 2030 (Paul, 2009). So, it is evident that in coming decades, megacity like Dhaka will have

to face acute water crisis. Drinking water management in the City is facing challenges. And to overcome the

consequences of water scarcity, a few water conservation and recycling techniques such as Rain Water Harvesting

(RWH), Decentralized Wastewater Treatment System (DEWATS), installation of water efficient fixtures and

appliances, and other similar methods are currently on hand to help conserve water. The paper focused on the

potentials of these techniques for residential buildings in Dhaka. To manage the increasing water demand and to

help conserve water, it also outlines the role of architects in integrating these techniques in typical residential plots

where the FAR rules are being or will be applied.

* Corresponding author: nawrose@uap-bd.edu

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2. WATER CRISIS IN DHAKA

Dhaka, the capital city of Bangladesh is ranked as the ninth largest urban agglomerations in the world. It holds

the highest average annual urban population growth rate of 5.6% from 1975-2007 (UNESCAP, 2010). Dhaka Water

Supply and Sewerage Authority (DWASA) is the responsible body to supply water to this huge population. Total

water demand in Dhaka city varies from 2100 to 2300 MLD with seasonal variation. However, total production

capacity of DWASA is 2250 MLD. However, DWASA has never reached its production target and actual

production for groundwater and surface water is 1831.20 MLD and 256.30 MLD respectively (Table 1) with a

demand-supply gap of 160 MLD.

2.1. Demand, Supply and Deficit of Water

91% of the total water served by DWASA is utilized to meet the domestic water demand and about 9% is

supplied to industrial and commercial sectors. DWASA projects total water demand considering per person per day

water demand as 150 liter and accordingly supplies water to the city dwellers. But the statistics imply that almost

half of the population in Dhaka city are deprived of getting DWASA projected standard water requirement. Table 1

shows that Almost 94% of water supply comes from underground water and Dhaka continues to withdraw

groundwater for its 88% of supply (Table 1).

Table 1: Water Production Scenario of DWASA (DWASA, 2010)

Source Production

Capacity

Actual Production Source wise %

of production

No. of DTWs

and SWTPs MLD % of Capacity

Ground Water 1948.30 1831.20 93.99 87.72 560

Surface Water 299.17 256.30 85.67 12.28 4

Total 2247.47 2087.50 92.88 100.00

Figure1 shows the demand supply and deficit trend for Dhaka city since 1963. The total water demand for Dhaka

city was increased from 150 MLD in 1963 to 2180 MLD in 2010. In 1963 the total deficit for water supply in Dhaka

city was 20 MLD which substantially increased to 190 MLD in 2010. In 1963, DWASA supplied water for 0.85

million people which substantially increased to 14.5 million in 2010. It is predicted that unless new treatment plants

are erected or come into operation in response to increased demand starting at 2040, DWASA will experience 704.3

MLD supply deficit by 2050 (Uddin and Baten, 2011).

Figure 1: Demand, Supply and Deficit of Water in Dhaka City (DWASA, 2011)

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2.2. Ground Water Depletion

Rapid urbanization including construction of buildings, roads, and other structures, is continuously hindering the

natural groundwater recharges from rainfall and perennial water sources existing in and around the city. According

to Roy (2003), the decline is to be more severe mainly to the city centre where concrete coating prevents recharge of

the groundwater level from the rainwater. In Dhaka, the depletion rate is 2.5 to 3.5 meters per year and the upper

aquifer of Dhaka has already exceeded its withdrawal limit (Mahmud, 2009). If the water level goes down to 70

meters due to continuation of the present rate of extraction of groundwater, a large number of DWASA pumps will

become inoperative. The groundwater of Dhaka will dry up by the year 2016 if the present decline in its water level

continues due to unabated extraction (Khan, 2007). For this, the Government is mulling over making water

recharging facilities mandatory in the proposed National Building Code, prepared by the Ministry of Housing and

Public Works. Rajdhani Unnayan Kartripakkha (RajUK) also tries to incorporate the same requirement in the

upcoming Building Construction Rules 2012 (Alam, 2012).

2.3. Surface Water Pollution

Though the city is surrounded by four rivers Buriganga, Balu, Turag and Tongi Khal, only about 12.28% of

supplied water, as showed in Table 1 is obtained from the rivers. Water of these surrounding rivers and lakes has

already exceeded the standard limits of many water quality parameters because of the discharge of huge amount of

untreated and municipal wastes (Biswas et.al. 2010). The water quality of any of these are so degraded that they are

completely unusable for any domestic or even bathing purposes, particularly in the dry season. In order to reduce its

dependence on groundwater and shift its reliance to surface water, DWASA is currently doing feasibility studies and

negotiating with donors for the construction of three surface water treatment plants (Saidabad Phase II and III,

Padma/Pagla and Khilkhet). The treatment plants will draw water from more distant and less polluted rivers up to

160 km from the city and are expected to add an additional 1400 MLD capacity (Gunawansa & Hoque, 2012).

3. DOMESTIC WATER CONSUMPTION PATTERN

As Dhaka’s population is rising, modern apartment blocks - built by one of the hundreds of real estate companies

in the City, are springing up everywhere and seem to be the most popular housing choice for millions of city

dwellers. These apartment complexes may consist from 4 to as much as 100 flats. The indoor uses of water include

cooking, drinking, washing clothes, dishwashing, floor cleaning, bathing, flushing and hand washing and outdoor

uses are limited to car washing only. Cooking, toilet flushing, dish washing and cloth washing account for the

highest water use in the household (Gunawansa & Hoque, 2012).

Table 2: Domestic Water Consumption Pattern of a Typical Household of 6 Members.

Activity Frequency Specification Daily Water Use/ liters

Cooking & Food Preparation 350 liters/day 350

Drinking 2 liters/day 12

Toilet Flushing 4 flushes/person 12 liters/day 288

Faucet Use 4 minutes/day 8 liters/minute 192

Bathing / Shower 6 minutes/day 8 liters/minute 288

Cloth Washing 20 minutes/day 12 liters/minute 240

Dish Washing 250 liters/day 250

House Cleaning 60 liters/day 60

Car Washing 0.2 times/day 120 liters/wash 24

Bathroom Washing 3 nos. (2 times a week) 200 liters/wash 172

Total 1876

The individual amount mentioned in Table 2 provides an idea of the relative water use in different sectors in the

household. Assuming each household has around 6 members, the consumption per person per day is 310-330 liters.

It is essential to mention here that this amount is more than double of that DWASA projects (daily 150 liters per

capita). For this, water conservation through the reduction of demand and introduction of water recycling techniques

in each household has been considered as important components of water management for Dhaka.

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4. WATER CONSERVATION TECHNIQUES

4.1. Behavioral Change of User

Most of the time with today’s busy lifestyles, people are not fully aware of the amount of water consumed

(Randolph and Patrick, 2008), nor in which activities they consume the most. Since employing domestic maids is an

age old tradition in urban areas in Bangladesh, most clothes and dishes are washed by hand by housemaids. It is

often seen that those who are not constantly supervised by their employers, waste a lot of water by keeping the taps

open while washing clothes and dishes. Moreover, people’s eating and cooking habits are such that a lot of dishes

and crockery are used while cooking and eating. It has also been observed that kitchen faucets are much wider and

have higher flow rates compared to other faucets in the household. And these consumptions can be greatly

minimized through behavioral changes such as turning the tap off whilst washing teeth, or when shampooing; using

a water saving device in the toilet cistern; or running the washing machine only on full loads, soap all dishes at one

go with the tap closed and then rinse (Elizondo‐Elizondo, 2010).

4.2. Water Efficient Fixtures

In urban households like Dhaka, the points of water consumption are the water fixtures which include toilets,

faucets, showerheads, washing machines, dishwashers and sometimes urinals. The water consumption rates of these

appliances have decreased with technological innovation over time and today. Table 3 shows an estimate of the

volume of water that a person can save daily by replacing conventional appliances with water efficient fixtures.

Table 3: Estimated Water Savings from Water-Saving Devices (Gunawansa & Hoque, 2012; Modified by Author)

Fixture Frequency without water-

saving fixtures

(lpcd)

with water

saving fixtures

(lpcd)

with water

conserving

fixtures (lpcd)

Low flush toilet 5.1 flushes/day 93 37 56

Low flow showerheads 5.3 mins/day 72 61 12

Low flow faucets 4 mins/day 55 27 27

Front loading washing machine 0.37 loads/day 86 46 40

Water efficient dishwasher 0.1 loads/day 5 3 2

Total 311 174 137

Water conservation has been established as an essential practice in many developed nations worldwide. But, it is

not a popular concept in the developing countries like Bangladesh. The consumers are not much aware on this issue

of conservation and take almost no steps to minimize their domestic water use. Alternatively, The Government also

is not taking initiatives to bring this issue into consideration. Moreover, the consumers have little knowledge that

water efficient fixtures widely available in the market can lead to significant reductions in water use without

compromising performance. Here, Architects have significant role to play in convincing their clients to purchase

water efficient fixtures. They can notify them on this issue of water conservation and in ‘Construction stages’ of

building construction they can instruct the contractor to install these specific types of fixtures such as low flush

toilet, low flow showerheads, low flow faucets and other similar products.

5. WATER RECYCLING TECHNIQUES

5.1. Rain Water Harvesting (RWH)

Rain water harvesting is the capture, diversion, and storage of rainwater for a number of different purposes

including landscape irrigation, drinking and domestic use, aquifer recharge, and storm water abatement. It provides

inexpensive drinking water. This is a multipurpose way of not only recharging the ground water but also reducing

the runoff and water logging during the season of heavy rainfall. The traditional knowledge, skills and materials can

be used for this system. During rainy season individual can collect water on his rooftop and manage it on his own.

112 | F a t e m i , M . N . , I C E R I E 2 0 1 3

Reserved rain water can be used for self purposes or domestic use. If needed, a chemical treatment such as

chlorination can be used to purify the water. Rainwater harvesting to recharge the groundwater enhances the

availability of groundwater at a specific place and time and thus assures a continuous and reliable access to

groundwater.

Table 4: Demand and Supply of Rain Water for Flushing Toilets and Car Washing

Demand Calculation

Daily water consumption per person (Table 2) 48 + 4 52 lpcd

Total number of people (6 members/ household, 10 units,

ground floor for parking)

6 x 10 60 nos.

Scarcity period (3 months) 90 days

Rain water demand

0.052 x 90 x 60 281 m3

Supply Calculation

Catchment area (maximum ground coverage) 230 sqm

Run-off coefficient (for concrete) 0.8

Average yearly rainfall (for Dhaka) 2 m

Rain water harvesting potential 230 x 0.8 x 2 368 m3

Table 4 shows that for a typical residential plot (area of 335 sqm.) and maximum ground coverage (area of 230

sqm.) to store rainwater for the scarcity period (of 90 days) the storage tank should be of 300 m3. The rest of the

water can be diverted to the recharge well or recharge pit.

5.2. Decentralized Wastewater Treatment System (DEWATS)

Decentralized waste water treatment system can be practiced by an individual, or by a community consisting of

several buildings. For the urban areas like Dhaka, the components of DEWATS are Settler, Anaerobic Baffled

Reactor, Planted Filter Bed and Polishing Pond. Reclaimed water can be pumped into reservoir where it will mix

with and be diluted by storm water. This mixture of storm water and reclaimed water could then be treated again. In

a residential setting, treated grey water from sinks, baths, showers, or washing machines may be used to flush toilets,

for gardening or car washing.

Table 5: Space Requirement of Decentralized Waste Water Treatment System for a Typical Residential Plot

Population (P) (6 members/ household, 10 units, ground floor for parking) 60 nos.

Water use (w) (Table 2) 310 lpcd

Volume of water consumed (P x w) 18600 liters

Volume of waste water (v) (80% of total water consumption is waste) in m3 14.88 m

3

The peak hour flow Peaking factor {(18+√P)/(4+√P)} x average flow/hr (v/24) 2.66 m3/hr

Volume of sludge generated (s)

(0.0001 m3 per capita x day x P) 2.19 m

3

Area (As) of settler (0.5 sqm./m3 x v) 7.44 sqm.

Depth of settler (average flow/hr (v/24) X retention time (3 hrs) + s)/ As 0.54 m

Area (Abr) of baffled reactor (1 sqm./m3 x v) 14.88 sqm.

Depth of baffled reactor (ranges from 1.5 to 2 m) 1.5 m

Area (Afr) of planted filter bed (4 sqm./m3 x v) 59.52 sqm.

Depth of planted filter bed (between 0.6 to 1 m) 0.6 m

Area (App) of polishing pond (1.2 sqm./m3 x v) 17.86 sqm.

Depth of polishing pond (restricted to 1 to 1.5 m) 1 m

Table 5 shows that for a typical residential plot (area of 335 sqm.) and 60 numbers of people, the settler (area of

7.44 sqm.), anaerobic baffled reactor (area of 14.88 sqm.) and polishing pond (area of 17.86 sqm.) can be arranged

within the maximum ground coverage area and the planted filter bed (area of 59.52 sqm.) can be arranged in the

mandatory green area (area of 105 sqm.).

113 | F a t e m i , M . N . , I C E R I E 2 0 1 3

6. CONCLUSION

Crisis of drinking water is one of the critical challenges in Dhaka city. This problem cannot be solved overnight.

To use the surface water of the peripheral river would be a good option, but extreme pollution leads it beyond the

treatment level. Installation of more DTW by DWASA to meet the public demand should be stopped, though the

tremendous pressure on ground water aquifer exists. As a consequence, there is no other alternative but to undertake

the water conservation and recycling techniques to conserve the water and simultaneously to manage the demand.

Alternative water supply and ground water recharge system should be implemented on the basis of priority. Use of

water efficient fixtures and at the same time, change in water consumption behavior will also have to achieved.

7. REFERENCES

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Biswas, S. K., Mahtab, S. B. & Rahman, M. M. (2010) ‘Integrated Water Resources Management Options for

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Elizondo‐Elizondo, G. M., (2010) ‘Patterns of conservation and domestic water use in different cultures: a

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Gunawansa, A. and Hoque, S. F. (2012) ‘Urban Water Supply Challenges in Dhaka: Potential for Residential Water

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Khan, M. A. (2007) ‘Safe City: A Long Way to Go’, in Nazem, I. N. et al (eds), ‘A Safe City is a Just City’,

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Mahmud, M.A. (2009) ‘Ground Water Depletion and Environmental Consequences: A Case Study on Dhaka City’,

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Paul, R. (2009) ‘Water Security in Dhaka City-An initiative of Government of Bangladesh’, 6th

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Randolph, B. and Patrick, T. (2008) ‘Attitudes to conservation and water consumption’, Environmental Science &

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Roy, P. (2003) ‘Water: Plenty Yet Scarce’ In Dr. Atiur Rahman (eds.), ‘ECOFILE’, Vol. 6, No. 3&4, Unnayan

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Uddin A.F.M.A. and Baten, M.A. (2011) ‘Water Supply of Dhaka City: Murky Future’, Unnayan Onneshan-The

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session, General Comment No. 15,

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28 October 2012

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