Greywater Generation and Quality Measurement at a Specific Site In Dhaka City
INTRODUCTION
1.1 General Background
Water is a limited natural resource and fundamental for life and health. So we need to start thinking smarter about how we use it. We must think how to make sure our new or existing home uses water efficiently and cost effectively. With increasing pressures on water resources, the concept of beneficial use of treated wastewater has rapidly become an imperative for water agencies around the world. Water reclamation, recycling and reuse are now recognized as key components of water and wastewater management. Along with the technology advances in wastewater treatment, the opportunity for water reuse has never been more viable. The benefits of using recycled water include protection of water resources, prevention of coastal pollution, recovery of nutrients for agriculture, augmentation of river flow, savings in wastewater treatment, groundwater recharge, and sustainability of water resource management. However, given these benefits, water reuse should not be treated simply as a means to an end but should be implemented in conjunction with other water conservation measures.
Here comes the question of which type of water is compatible to reuse. As long as the problem is about the scarcity of water and no new sources can be developed in our country without the traditional underground water, surface water and some other sources of potable water, the only choice remain is to reuse the household water, which in environmental science is named as ‘Greywater’. Any wash water that has been used in the home, except water from toilets, is called Greywater. The introduction of Greywater recycling will surely give a lasting impetus to economy and society alike.
1.2 Historical Background and present condition
Today, when we enjoy the most incredible high-tech modern conveniences of the space research era like the mobile phone containing dozens of millions of transistors, enabling us even to watch TV, use the internet, e-mail, GPS, etc., some primitive problems remain stubbornly still with us, endangering our future. Such an unresolved case is the example of the flushing toilet for which we waist potable fresh water and this makes up about one third in household water consumption. To resolve this one and a half century-old problem a trivial and obvious solution has been found. Some thrifty and ingenious people mainly house wives collect the washing water with buckets and flush the toilet with that used washing water which is called grey-water.
Storm and sanitary sewers were necessarily developed along with the growth of cities. By the 1840s the luxury of indoor plumbing, which mixes human waste with water and flushes it away, eliminated the need for cesspools. Odor was considered the big problem in waste disposal and to address it, sewage could be drained to a lagoon, or “settled” and the solids removed, to be disposed of separately. This process is now called “primary treatment” and the settled solids are called “sludge”.
At the end of the 19th century, since primary treatment still left odor problems, it was discovered that bad odors could be prevented by introducing oxygen into the decomposing sewage. This was the beginning of the biological aerobic and anaerobic treatments which are fundamental to waste water processes.
By the 1920s, it became necessary to further control the pollution caused by the large quantities of human and industrial liquid wastes which were being piped into rivers and oceans, and modern treatment plants were being built in the US and other industrialized nations by the 1930s. Designed to make water safe for fishing and recreation, the clean water act of 1972 mandated elimination of the discharge of untreated waste from municipal and industrial sources, and the US federal government provided billions of dollars in grants for building sewage treatment plants around the country. Modern treatment plants, usually using sand filtration and chlorination in addition to primary and secondary treatment, were required to meet certain standards.
Current treatment improves the quality of separated wastewater solids or sludge. The separated water is given further treatment considered adequate for non potable use by local agencies, and discharged into bodies of water, or reused as reclaimed water. In places like Florida, where it is necessary to avoid nutrient overload of sensitive receiving water, reuse of treated or reclaimed water can be more economically feasible than meeting the higher standards for surface water disposal mandated by the clean water act.
Recent studies support long standing concerns about possible public health effects of reclaimed water. It has been known for some time that treated waste water effluent, or reclaimed water, contains pathogens that could be transferred to people through contact, including aerosols from sprinklers. Particularly worrisome are high levels of parasites such as giardia and cryptosporidium which are not killed by chlorination.
In 1997, the United States environmental protection agency warned, “(viable) bacteria from reclaimed water in sprinklers can travel more than 1000 feet in the air.” As far back as 1984, researchers concluded that disinfection by chlorination, an important part of wastewater treatment, initially lowers the total number of sewage related bacteria, but may substantially increase the proportions of antibiotic resistant, potentially pathogenic organisms.
More recently, Chang (2007) reported that staphylococcus aureus bacteria become more virulent and drug resistant after chlorination. A large study in 2006 confirms that microbes, inactivated but not killed by treatment, can re-grow in retention ponds and pipes, becoming a major source of the spread of multi-drug resistant pathogens in the environment. During the processing of reclaimed water, fragments can be released from microbes when their cell walls are disrupted. These fragments are not alive and not affected by disinfectants like chlorine. This intact genetic material can transfer both virulence and drug resistance to living microorganisms in water or soil. Amy pruden (2006) demonstrates that such genetic fragments pass through sewer water reclamation plants into rivers and into drinking water sources. Since the number and types of bacteria in a treatment plant are large, a positive environment exists for transfer of drug resistance. Independent scientists found that Santa Barbara’s reclaimed water contained chlorine resistant bacteria that were also resistant to eleven of the twelve antibiotics tested.
There is also concern in the industry about organic chemicals, including endocrine disruptors in wastewater. In 2005, the United States department of agriculture reported: “overall, the environmental and public health impacts of irrigation with reclaimed sewage effluent and the potential degradation of underlying groundwater are largely unknown.”
From the perspective of our country there is not much done to reuse the Greywater in household chores. It might be of aesthetical reasoning or lack of proper technological advancement. But some foreign technologies are nowadays getting available like ‘ozzi kleen grey water recycling system’, ‘marcuras water treatment pvt. Ltd.’, ‘engnet – sewage treatment’ are now getting available with their services.
1.3 Why this study?
Dhaka is the capital of Bangladesh and the principal city of Dhaka Division. Its area comprises of capital city of 304 km2 (117.4 sq mi) and water of 48.56 km2 (18.7 sq mi). It is a megacity and one of the major cities of South Asia. Located on the banks of the Buriganga River, Dhaka, along with its metropolitan area, has a population of over 12 million, making it the largest city in Bangladesh. It is the 9th largest city in the world and also among the most densely populated cities in the world. Being one of the largest mega cities of the world, Dhaka is facing continuing potable water -related problems over the last few decades. About 10 million people representing about 30% of the total urban population live in this capital city of the country. The population of the city is rapidly increasing each day since this city is the center of all sorts of financial, business, medical, educational and political facilities and services. The disproportionate rise in the urban population has created severe pressure on existing infrastructure and services, including water supply, sanitation, sewerage and drainage services. The environmental conditions in most part of the city are poor, with direct discharges of human and industrial wastes into river systems, possible contamination of groundwater from lack of adequate sewerage systems, direct industrial disposals and inadequate management of solid waste disposal.
On the other hand, due to increasing population and industrial growth the demand for fresh drinking water is rising rapidly. In Dhaka city, Water and Sewerage Authorities (WASA) are responsible for municipal water supplies. Presently, Dhaka WASA is producing 1160.21 Ml/day for the urban water supply from about 389 deep tube wells (DTW). About 84.33% of the municipal water supply for the domestic use comes mostly from the groundwater of the city. In addition, over 500 private tube wells of different depths also exist in this city, which are estimated to supply about 300 Ml/day, mainly to commercial and industrial users.
Available records and some groundwater related researches show that the groundwater abstraction in the city has increased by several hundred percent in last few decades. In 1980 about 112 million cubic meters groundwater was withdrawn from about 80 tube wells to meet the ongoing demands of the city. But the need for groundwater increased so high that in 1990 about 136 tube wells were used to withdraw about 183 million cubic meters of groundwater. Presently, about 389 tube wells are producing about 1160.21 Ml/day of groundwater which can be projected to about 423 million cubic meters for the running year. Groundwater currently provides about 97% of Dhaka’s water demand.
In many parts of the city the condition of the main aquifer has been changed from confined to an unconfined condition. Such change in the hydrodynamic condition can make the aquifer vulnerable to possible groundwater contamination, and also impede groundwater supply by tube wells. Many research projects have ultimately ended up with the finding that the groundwater table of Dhaka city is dropping at a very high rate with time as indicated by long term hydrographs. The city’s groundwater level has dropped about 20 meters over the last six years or more than 3 meters in a year on an average, according to a government survey. It is recoded that the drop in water level drastically increased in the late 80’s.
Figure 1.1: Year-wise depletion of groundwater
Data also suggested that in 1990 the depth to the water table in the peri-urban areas was about 4 meters and in the central region it was about 15 meters. However, in 2002, the water level in the city center (Motijheel area) was about 50 meters below mean sea level. WASA personnel also reported that their groundwater studies has revealed that the water table is declining two to three meters every year in Dhaka city and the intensity is high in and around the Motijheel commercial area. Such water level condition allows groundwater to flow towards the depressed city center from the peripheral areas.
Figure 1.2: Groundwater depletion situation in the capital
Various reasons are responsible for continuous groundwater drop in this city of which high groundwater withdrawal from the aquifer is the most crucial one. In addition, rapid urbanization including construction of roads, buildings, and other engineering structures, flood protection dams and embankments is continuously hindering the natural groundwater recharges from rainfall and perennial water sources existing in and around the city.
Disappearances of many lakes, canals, and small rivers in and around the city also depreciated groundwater recharge. Reports say that a network of 22 canals that facilitated the natural drainage for the floodwaters and groundwater recharge in this city has disappeared or shrunk over the last four decades. All these anthropogenic activities gradually obstructed the natural groundwater recharge, conversely deteriorated the water table condition over the last few decades.
The first water supply system was introduced in Dhaka by the British in 1888 under the jurisdiction of the district civil surgeon at Chandighat. The first deep-water pump was installed in Dhaka in 1949. Till the end of 1960s the water supply in Dhaka was almost surface-water system based. The dependence on groundwater for domestic, industrial, and commercial water supply in the city area was more than 95 per cent prior to the commissioning of a surface water treatment plant (Sayedabad Surface Water Treatment Plant) in 2002. The ground water layer in the city, in fact, is dropping by around three metres a year on an average. According to hydrogeologists, this not only exacerbates the already sever water crisis but will in the future, cause land to subside. Already most of the available water of the upper aquifer layer has been used up. Now Wasa is installing deep aquifer pumps to abstract water from the second layer. But even this is becoming difficult in many areas of Dhanmondi, Mirpur, Niketan, Nakhalpara, Ibrahimpur and Manipur. Water Crisis – total shortfall is now 500 million liters per day. Due to above circumstance it is high time we realized the value of fresh water availability in our city. This study actually encourages the people to reuse Greywater and decrease the wastage of fresh water.
1.4 Objectives of the study
The objectives of the study are:
1. Estimation of water use in household chores and find out the amount of grey water produced.
2. Characterization of the greywater.
1.5 Methodology
In order to estimate the water use in household chores and find out the amount of grey water produced at first we fixed the locations where we could get suitable environment to complete our task. Considering many things we selected two spots at Agargaon & Tejgaon area for our study. The determination of water use is done for two categories of days-working day & holiday. In case of Agargaon area it was quite easy for us to do the tusk as we live here. Here we determined the amount of water used for cloth wash, bathing, utensils & cooking, floor wash, hand wash, ablution, drinking purpose, bathroom wash and toilet flushing(overall covering the total household use). In order to determine the amount of black water generated a day, the amount of water being used in the toilet flushing is calculated. Then the amount of greywater is calculated by subtracting the amount of black water from total water use. In case of Tejgaon area it was not possible to go to that house several times and estimate the water use too accurately. So we did a questionnaire survey among the household members. For qualitative analysis of greywater we collected sample from Agargaon only. Here three types of samples are collected-(i) cloth wash (without detergent, wash water, rinse water), (ii) basin water & (iii) bathing water. Then we tested our samples in BUET environmental laboratory. We tested five water quality parameters- (i) pH (ii) color (iii) turbidity (iv) COD (v) BOD5 .
1.7 Organization of the report
Chapter 1: Includes background and present condition, objectives, why this study and methodology of this study.
Chapter 2: Includes literature review covering definition of Greywater, reason behind using it, benefits of Greywater recycling, environmental impact of using Greywater, Greywater generation and quality
Chapter 3: Greywater generation, ways of collection, analysis and recycling process.
Chapter 4: Presents the results with graphs and pie charts and a general discussion on the recycling process of different area.
Chapter 5: Conclusions and recommendations.
LITERATURE REVIEW
2.1 General
Greywater is non-industrial wastewater generated from domestic processes such as dish washing, laundry and bathing. Greywater comprises 50-80% of residential wastewater. Greywater comprises wastewater generated from all of the house’s sanitation equipment except for the septic tank (water from toilets is blackwater, or sewage). Greywater is distinct from blackwater in the amount and composition of its chemical and biological contaminants (from feces or toxic chemicals). Greywater gets its name from its cloudy appearance and from its status as being neither fresh (white water from groundwater or potable water), nor heavily polluted (blackwater). According to this definition, wastewater containing significant food residues or high concentrations of toxic chemicals from household cleaners, etc., may be considered “dark grey” or dirty water.
In recent years, concerns over dwindling reserves of groundwater and overloaded or costly sewage treatment plants have generated much interest in the reuse or recycling of Greywater, both domestically and for use in commercial irrigation. However, concerns over potential health and environmental risks mean that many jurisdictions demand such intensive treatment systems for legal reuse of Greywater that the commercial cost is higher than for fresh water. Despite these obstacles, Greywater is often reused for irrigation, illegally or not. In drought zones or areas hit by hose pipe bans (irrigation restrictions), Greywater can be harvested informally by manual bucketing. In the third world, reuse of Greywater is often unregulated and is common. At present, the recycling of Greywater is poorly understood compared with elimination.
Greywater is wash water. That is, all wastewater excepting toilet wastes and food wastes derived from garbage grinders. There are significant distinctions between Greywater and toilet wastewater (called “blackwater”). These distinctions tell us how these wastewaters should be treated /managed and why, in the interests of public health and environmental protection, they should not be mixed together.
2.2 Why use Greywater?
It’s a waste to irrigate with great quantities of drinking water when plants thrive on used water containing small bits of compost. Unlike a lot of ecological stopgap measures, greywater reuse is a part of the fundamental solution to many ecological problems and will probably remain essentially unchanged in the distant future. The benefits of greywater recycling include:
- Lower fresh water use
- Less strain on failing septic tank or treatment plant
- Better treatment (topsoil is many times more effective than subsoil or treatment plant)
- Less energy and chemical use
- Groundwater recharge
- Plant growth
- Reclamation of otherwise wasted nutrients
- Increased awareness of and sensitivity to natural cycles
- Greywater contains far less nitrogen than blackwater
Nine-tenths of the nitrogen contained in combined wastewater derives from toilet wastes (i.e., from the blackwater). Nitrogen is one of the most serious and difficult to remove pollutants affecting our potential drinking water supply.
- Greywater contains far fewer pathogens than blackwater
Medical and public health professionals view feces as the most significant source of human pathogens. Keeping toilet wastes out of the wastewater stream dramatically reduces the danger of spreading such organisms via water.
- Greywater decomposes much faster than blackwater.
The implication of the more rapid decomposition of Greywater pollutants is the quicker stabilization and therefore enhanced prevention of water pollution.
2.3 Why Does Greywater Matter?
Viewed narrowly, greywater systems don’t look that important. A low flow showerhead can save water with less effort. A septic system can treat greywater almost as well.But when we look at the whole picture—how everything connects—the keystone importance of greywater is revealed.
Ecological systems design is about context, and integration between systems. The entirety of integrated, ecological design can be reduced to one sentence: do what’s appropriate for the context.
Ecological systems—rainwater harvesting, runoff management, passive solar, composting toilets, edible landscaping—all of these are more context sensitive than their counterparts in conventional practice; that’s most of what makes them more ecological.
Greywater systems are more context sensitive than any other manmade ecological system, and more connected to more other systems.
Many people and organizations instinctively recognize that greywater is the ideal test case for the transition to a new way of regulating and building that is appropriate to a post-peak resource, mature civilization.
The US Green Building Council, the City of Santa Barbara, CA, Oregon ReCode, and SLO Green Build are among those organizations which independently chose greywater standards as the technology with which to launch their programs of regulatory reform.
· Lower fresh water use
· Greywater can replace fresh water in many instances, saving money and increasing the effective water supply in regions where irrigation is needed. Residential water use is almost evently split between indoor and outdoor. All except toilet water could be recycled outdoors, achieving the same result with significantly less water diverted from nature.
· Less strain on septic tank or treatment plant
· Greywater use greatly extends the useful life and capacity of septic systems. For municipal treatment systems, decreased wastewater flow means higher treatment effectiveness and lower costs.
· Highly effective purification
· Greywater is purified to a spectacularly high degree in the upper, most biologically active region of the soil. This protects the quality of natural surface and ground waters.
· Site unsuitable for a septic tank
· For sites with slow soil percolation or other problems, a greywater system can be a partial or complete substitute for a very costly, over-engineered system.
· Less energy and chemical use
· Less energy and chemicals are used due to the reduced amount of both freshwater and wastewater that needs pumping and treatment. For those providing their own water or electricity, the advantage of a reduced burden on the infrastructure is felt directly. Also, treating our wastewater in the soil under your own fruit trees definitely encourages us to dump fewer toxic chemicals down the drain.
· Groundwater recharge
· Greywater application in excess of plant needs recharges groundwater.
· Plant growth
· Greywater enables a landscape to flourish where water may not otherwise be available to support much plant growth.
· Reclamation of otherwise wasted nutrients
· Loss of nutrients through wastewater disposal in rivers or oceans is a subtle, but highly significant form of erosion. Reclaiming nutrients in greywater helps to maintain the fertility of the land.
· Increased awareness of and sensitivity to natural cycles
· Greywater use yields the satisfaction of taking responsibility for the wise husbandry of an important resource.
2.4 Application of recycled Greywater:
Irrigation:
Greywater typically breaks down faster than blackwater and has much less nitrogen and phosphorus. However, all Greywater must be assumed to have some blackwater-type components, including pathogens of various sorts. Greywater should be applied below the soil surface where possible (e.g., in mulch-filled trenches) and not sprayed, as there is a danger of inhaling the water as an aerosol.
However, long term research on Greywater use on soil has not yet been done and it is possible that there may be negative impacts on soil productivity. If we are concerned about this, use of laundry powders should be avoided; these often contain high levels of salt as a bulking agent, and this has the same effect on soil as a drought.
Indoor reuse
Recycled greywater from showers and bathtubs can be used for flushing toilets in most European and Australian jurisdictions and in United States jurisdictions that have adopted the International Plumbing Code.
Such a system could provide an estimated 30% reduction in water use for the average household. The danger of biological contamination is avoided by using:
- a cleaning tank, to eliminate floating and sinking items
- an intelligent control mechanism that flushes the collected water if it has been stored long enough to be hazardous; this completely avoids the problems of filtration and chemical treatment
The Uniform Plumbing Code, adopted in some United States jurisdictions, prohibits greywater use indoors.
Extreme living conditions
Greywater use promotes the ability to build in areas unsuitable for conventional treatment, or where conventional treatment is costly. The Mars Desert Research Station uses greywater recycling, and might be used on trips to Mars to reduce water consumption and increase oxygen generation.
Heat reclamation
Devices are currently available that capture heat from residential and industrial greywater, through a process called drainwater heat recovery, greywater heat recovery, or hot water heat recycling.
Rather than flowing directly into a water heating device, incoming cold water flows first through a heat exchanger where it is pre-warmed by heat from greywater flowing out from such activities as dishwashing, or showering. Typical household devices receiving greywater from a shower can recover up to 60% of the heat that would otherwise go to waste.
Ecology
Because greywater use, especially domestically, reduces demand on conventional water supplies and pressure on sewage treatment systems, its use is very beneficial to local waterways. In times of drought, especially in urban areas, greywater use in gardens or toilet systems helps to achieve the goals of ecologically sustainable development.
Suitable for drinking
In most locations, reclaimed water is not directly mixed with potable (drinking) water for several reasons:
Utilities providing reclaimed water for non-potable uses do not treat the water to drinking water standards.
Varying amounts of pathogens, pharmaceutical chemicals (e.g., hormones from female hormonal contraction) and other trace chemicals are able to pass through the treatment and filtering process, potentially causing danger to humans. Modern technologies such as reverse osmosis may help to somewhat overcome this problem. An experiment by the University of New South Wales reportedly showed a reverse osmosis system removed ethinylestradiol and paracetamol from the wastewater, even at 1000 times the expected concentration.
Drinking water standards were developed for natural ground water, and are not appropriate for identifying contaminants in reclaimed water. In addition to pathogens, and organic and endocrine disrupting chemicals, a large number of compounds may be present in reclaimed water. They cannot all be tested for, and there is a paucity of toxicity information on many of the compounds. Because of this, state regulatory agencies do not allow reclaimed water to be used for drinking, bathing, or filling swimming pools. They also warn those who use reclaimed water for irrigation to place a sign on their property warning people not to drink from the irrigation system, and to not use it directly on fruits or vegetables.
2.5 Possible Improvements in treatment
As world populations require both more clean water and better ways to dispose of wastewater, the demand for water reclamation will increase. Future success in water reuse will depend on whether this can be done without adverse effects on human health and the environment.
In the United States, reclaimed waste water is generally treated to secondary level when used for irrigation, but there are questions about the adequacy of that treatment. Some leading scientists in the main water society, AWWA, have long believed that secondary treatment is insufficient to protect people against pathogens, and recommended adding at least membrane filtration, reverse osmosis, ozonization, or other advanced treatments for irrigation water.
Seepage of nitrogen and phosphorus into ground and surface water is also becoming a serious problem, and will probably lead to at least tertiary treatment of reclaimed to remove nutrients in future. Even using secondary treatment, water quality can be improved. Testing for pathogens using Polymerase Chain Reaction (PCR) instead of older culturing techniques, and changing the discredited fecal coliform “indicator organism” standard would be improvements.
In a large study treatment plants showed that they could significantly reduce the numbers of parasites in effluent, just by making adjustments to the currently used process. But, even using the best of current technology, risk of spreading drug resistance in the environment through wastewater effluent, would remain.
Some scientists have suggested that there need to be basic changes in treatment, such as using bacteria to degrade waste based on nitrogen (urine) and not just carbonaceous (fecal) waste, saying that this would greatly improve effectiveness of treatment. Currently designed plants do not deal well with contaminants in solution (e.g. pharmaceuticals). “Dewatering” solids is a major problem. Some wastes could be disposed of without mixing them with water to begin with. In an interesting innovation, solids (sludge) could be removed before entering digesters and burned into a gas that could be used to run engines.
Emerging disinfection technologies include ultrasound, pulse are electrohydrolic discharge, and bank filtration. Another issue is concern about weakened mandates for pretreatment of industrial wastes before they are made part of the municipal waste stream. Some also believe that hospitals should treat their own wastes. The safety of drinking reclaimed water which has been given advanced treatment and blended with other waters remains controversial.
2.6 Worldwide acceptance
The leaders in use of reclaimed water in the U.S. are Florida and California, with Irvine Ranch Water District as one of the leading developers. They were the first district to approve the use of reclaimed water for in-building piping and use in flushing toilets.
As Australia continues to battle the 7-10 year drought, nationwide, reclaimed effluent is becoming a popular option. Two major capital cities in Australia, Adelaide and Brisbane, have already commited to adding reclaimed effluent to their dwindling dams. Brisbane has been seen as a leader in this trend, and other cities and towns will review the Western Corridor Recycled Water Project once completed. Goulbourn,Canberra, Newcastle, and Regional Victoria, Australia are already considering building a reclaimed effluent process.
According to an EU-funded study, “Europe and the Mediterranean countries are lagging behind” California, Japan, and Australia “in the extent to which reuse is being taken up.” According to the study “the concept (of reuse) is difficult for the regulators and wider public to understand and accept.”
Other alternatives
In urban areas where climate change has threatened long-term water security and reduced rainfall over catchment areas, using reclaimed water for indirect potable use may be superior to other water supply augmentation methods. One other commonly-used option is seawater desalination. Recycling wastewater and desalinating seawater may have many of the same disadvantages, including high costs of water treatment, infrastructure construction, transportation, and waste disposal problems. Although the best option varies from region to region, desalination is often superior economically, as reclaimed water usually requires a dual piping network, often with additional storage tanks, when used for non-potable use.
A less elaborate alternative to reclaimed water is a Greywater system. Greywater is wastewater that has been used in sinks, baths, showers, or washing machines, but does not contain sewage. In a home system, treated or untreated Greywater may be used to flush toilets or for irrigation. Some systems now exists which directly uses Greywater from a sink to flush a toilet or even combine the two into one piece of furniture.
Perhaps the simplest option is a rainwater harvesting system. Although there are concerns about the quality of rainwater in urban areas, due to air pollution and acid rain, many systems exist now to use untreated rainwater for non-potable uses or treated rainwater for direct potable use. There are also concerns about rainwater harvesting systems reducing the amount of run-off entering natural bodies of water.
2.7 Greywater and the environment
The potential ecological benefits of Greywater recycling include:
· Lower fresh water extraction from rivers and aquifers
· Less impact from septic tank and treatment plant infrastructure
· Topsoil nutrification
· Reduced energy use and chemical pollution from treatment
· Groundwater recharge
· Plant growth
· Reclamation of otherwise misdirected nutrients
· Greater quality of surface and ground water when preserved by the natural purification in the top layers of soil than generated water treatment processes
2.8 Greywater generation and quality
Water use in other countries
For the purpose of successful implementation of greywater recycling different countries of the world have already started the quantification of greywater generation and also the characterization of greywater. The available criteria of indoor household water use for the Republic of Korea, China, Sweden, UK and USA ( Zhang & Brown, 2005; Bradely, 2004; Eriksson et al., 1999) is presented in Table 1.
Table 1: Indoor Household Water Use
| Use | Korea
(% of total use) |
China
(% of total use) |
Sweden
(% of total use) |
UK
(% of total use) |
USA
(% of total use) |
| Bathing | 23 | 20 | 33 | 26 | 30 |
| Toilet | 45 | 21 | 22 | 34 | 21 |
| Laundry | 11 | 20 | 17 | 12 | 24 |
| Kitchen | 20 | 39 | 28 | 28 | 25 |
In most countries, guidelines and standards for water reuse in buildings either do not exist or are being revised or expanded. The available criteria for water reuse for toilet flushing (EPA, 1992) is presented in Table 2. No separate criteria for water reuse for laundry have been reported in the literature. However, criteria for domestic water recycling are available ( Surendran & Wheatley, 1998). These values are also included in Table 2.
Table 2: standards and criteria/ guidelines for water reuse for toilet flushing and domestic water recycling
| Parameter | Toilet flushing | Domestic water recycling | ||||||
| US | Japan | WHO | USEPA | USA NSF | Australia | UK | Germany | |
| pH | 6-9 | 5.8-8.6 | 6-9 | 6-9 | ||||
| BOD5
(mg/l) |
?10 | 10 | 20 | 20 | ||||
| Turbidity
(NTU) |
?2 | 5 | 2 | 1-2 | ||||
| TC
(no./100ml) |
1000(m) 200(g) | <10 | <1 | ND | 100 | |||
| FC
(no./100ml) |
ND | ?10
(E.Coli) |
<10 | <240 | <4 | 10 | ||
| Residual Cl2(mg/l) | 1 | Retain d* | ||||||
| Odor | odorless | NU | ||||||
| Appearance | NU | |||||||
ND = not detectable; NU = not unpleasant
(m) = mandatory; (g) = guideline
* at last holding tank in distribution line
The following are the requirements of greywater parameters that must be met in the agricultural sector:
Table 3: Parameters to Use Greywater on the Agricultural Sector
| Parameters | Maximum Permitted Values |
| pH | 6.5 – 8.5 |
| Conductivity (Ds/cm) | 2000 |
| BOD (mg/L) | 120 |
| COD (mg/L) | 200 |
| Total Suspended Solid (mg/L) | 120 |
| Fecal coliform (MPN/100 mL) | 1000 |
Source: M. Platzer, V. Caceres, dan N. Fong, 2004
QUANTIFICATION OF GREYWATER GENERATION
3.1 General
The main aim of this thesis work is to find out the generation rate of the greywater. Two different areas in the city have been surveyed for the data. These areas are:
1. Agargaon
2. Tejgaon
3.2 Way of working
3.2.1 Chosen Fields of water use
1. Cloth wash
2. Bathing
3. Utensils & Cooking
4. Floor wash
5. Hand wash
6. Ablution
7. Drinking purpose
8. Bathroom wash
9. Gardening
10. Car washing
11. Toilet flushing
3.2.2 Working Procedure
Working procedures of every sector of water use are described below:
(i) Cloth wash: Cloth wash is done by the housemaid daily. At first we observed her whole cloth wash procedure one day. Then we identified the bucket used for cloth wash & counted the number of that bucket of water used for cloth wash. After that we measured the volume of bucket by filling up the bucket with water by a known volume of bottle. So the total amount of water used for cloth wash daily can be obtained by multiplying the bucket volume with the number of use.
(ii) Bathing: For this purpose at first we selected a fixed bowl. Then the household members are requested to count the number of that bowl of water used for bathing. After that we measured the volume of bowl by filling up the bowl with water by a known volume of bottle. So the total amount of water used for bathing can be found by multiplying the bowl volume with the number of use for each member.
(iii) Utensils & Cooking: This was the most difficult to estimate, because utensils & cooking procedure continue for a long period of time. In this case we determined the volume of kitchen sink at first. For this the hole of the sink is being blocked by a cork. Then the sink is filled up with water up to a given mark by a bottle of known volume. So the volume of sink can be found by multiplying the volume of bottle with number of bottle used for filling up the sink. Then the cork was put up and let the water pass by the hole. Next the hole is again being closed by the cork. Then the sink is again filled up with water coming from the tap. The tap is operated at a medium speed. This time the time required for filling up the sink up to that given mark by tap water is counted. These two informations- the volume & the time will help us later for further calculation. We observed the ways of water using for this purpose one day. Then another day we tried to estimate the amount of used water. For this we counted the time how long the kitchen tap was remained on for whole utensils & cooking procedure. As we know the volume of water used for a unit time, so now the total volume of water used for utensils & cooking can be determined.
|
|
|
||||||
|
|
|||||||
Measuring Bottle
Figure 3.1: Measuring the volume of kitchen sink
(iv) Floor wash: Floor wash is done by the housemaid only. At first we identified the bucket used for this purpose. Then we determined the bucket volume by the process discussed earlier. And the maid was asked about the number of bucket being used for this work. The total amount being found here is almost equally divided among the family members.
(v)Hand wash: People may wash their hand after various activities, i.e. after returning home from outside, having some dusty works, before & after the meal etc. At first we determined the basin volume by the same process as used for kitchen sink. And also we counted the time required for filling up the basin with water coming from tap. Then we observed the time one used for hand wash. The time varies from person to person.
Figure 3.2: Measuring the volume of basin
(vi)Ablution: As ablution is an essential part of all activities in a Muslim family. We also estimated the water used for this purpose. As the basin volume and the time required for filling up that volume with water are known to us, we only counted the time one used for ablution.
(vii)Drinking purpose: We actually assumed minimum amount of water that one should drink daily generally and that is 2L.
(viii) Bathroom wash: This is done per week by the housemaid. We observed the whole procedure one day. Then another day we estimated the amount of water used for that purpose.
(ix)Gardening: As the two houses we selected do not have a garden, so we did not need to estimate the water used for this purpose.
(x)Car washing: As the two houses we selected do not own a car, so we did not need to estimate the water used for this purpose.
(xi)Toilet flushing: As we know the volume of flush that is about 10.5L, we only used to keep a list of house members & count the no. of times one did toilet flushing over the whole day.
3.3 Analysis of the Data
Water Consumption at Agargaon Area
Address: 3A, Al-Amana House
105/2/1, West Agargaon, Dhaka-1207
Table 4: No. of members: 2
| male | female | |
| Adult | – | 2 |
| Working Member | – | 1 |
Date: 05/06/2010
Table 5: Water use on Working Day
| Field of using | Quantity (lpcd) |
| Cloth wash | 27 |
| Bathing | 30 |
| Utensils & Cooking | 24 |
| Floor wash | 15 |
| Hand wash | 8 |
| Ablution | 8.75 |
| Drinking purpose | 2 |
| Bathroom wash(done per week)
(No. Of Bathroom:2) |
6 |
| Gardening | – |
| Car washing | – |
| Toilet flushing(10.5L commode) | 68.25 |
| Total | 189 |
Date: 03/06/2010
Table 6: Water use on Holiday
| Field of using | Quantity (lpcd) |
| Cloth wash | 27 |
| Bathing | 30 |
| Utensils & Cooking | 24 |
| Floor wash | 15 |
| Hand wash | 11 |
| Ablution | 12.5 |
| Drinking purpose | 2 |
| Bathroom wash(done per week)
(No. Of Bathroom:2) |
6 |
| Gardening | – |
| Car washing | – |
| Toilet flushing(10.5L commode) | 84 |
| Total | 211.5 |
Figure 3.3: Water consumption on working day
Figure 3.4: Water Consumption on holiday
From these above charts, we could easily find out the following things:
· Amount of water used in toilet flushing is less on working day than holiday. It happens because of the absence of one member for a fixed office hours. The little variation in case of hand wash & ablution occurs due to the same reason.
· Amount of water used for cloth wash, utensils & cooking, floor wash and bathroom wash remains almost the same for working day & holiday. This is because these things are done regularly by the same person (housemaid).
Figure 3.5: Greywater generation on both working day & holiday
On both days-working day and holiday, almost 60-70% of total water use is greywater.
Figure 3.6: Indoor Household Water Use in Both Working day & Holiday
Table 7: Indoor Household Water Use in other countries
| Use | Korea
(% of total use) |
China
(% of total use) |
Sweden
(% of total use) |
UK
(% of total use) |
USA
(% of total use) |
| Bathing | 23 | 20 | 33 | 26 | 30 |
| Toilet | 45 | 21 | 22 | 34 | 21 |
| Laundry | 11 | 20 | 17 | 12 | 24 |
| Kitchen | 20 | 39 | 28 | 28 | 25 |
Comparison with other countries
· From Table-1, it is clear that like other countries in ours a significant amount of supplied water to households is used for toilet flushing.
· Amount of water used for bathing (as % of total use) is close to that of China.
· Amount of water used for toilet flushing (% of total use) is close to that of UK.
· Amount of water used for laundry (% of total use) is close to that of Korea & UK.
· Amount of water used for kitchen use (as % of total use) is close to that of Korea.
Water consumption according to WASA Bill:
Address: Al-Amana House
105/2/1, West Agargaon, Dhaka-1207
No. Of Floor: 6
No. Of Unit: 2
Total Person: 60
Year: 2009
Table 8: Water consumption according to WASA Bill
| Month | Water Consumption(l) | Water Consumption(lpcd) |
| January | 600000 | 323 |
| February | 600000 | 357 |
| March | 570000 | 306 |
| April | 510000 | 283 |
| May | 520000 | 280 |
| June | 600000 | 333 |
| July | 600000 | 323 |
| August | 650000 | 349 |
| September | 650000 | 361 |
| October | 600000 | 323 |
| November | 550000 | 306 |
| December | 700000 | 376 |
| Total | 7150000 | 3920 |
| Average | 327 |
Water Consumption at Tejgaon Area:
Address: 233 D.M.C.,
Old 158 West Nakhalpara, Tejgaon, Dhaka.
Table 9: No. Of members: 8
| male | female | |
| Adult | 3 | 4 |
| Children | – | 1 |
| Working Member | 2 | 2 |
Table 10: Water use on Working Day
| Field of using | Quantity (lpcd) |
| Cloth wash | 33 |
| Bathing | 36 |
| Utensils & Cooking | 30 |
| Floor wash | 20 |
| Hand wash | 8.5 |
| Ablution | 12.5 |
| Drinking purpose | 2 |
| Bathroom wash(done per week)
(No. of Bathroom:3) |
7.5 |
| Gardening | – |
| Car washing | – |
| Toilet flushing(10.5L commode) | 77 |
| Total | 226.5 |
Table 11: Water use on Holiday
| Field of using | Quantity (lpcd) |
| Cloth wash | 33 |
| Bathing | 40 |
| Utensils & Cooking | 30 |
| Floor wash | 20 |
| Hand wash | 11.5 |
| Ablution | 13 |
| Drinking purpose | 2 |
| Bathroom wash(done per week)
(No. of Bathroom:3) |
7.5 |
| Gardening | – |
| Car washing | – |
| Toilet flushing(10.5L commode) | 93 |
| Total | 250 |
Figure 3.7: Water consumption on working day
Figure 3.8: Water consumption on holiday
From these above charts, we could easily find out the following things:
· Amount of water used in toilet flushing is less on working day than holiday. It happens because of the absence of four members for a fixed office hours. The little variation in case of hand wash & ablution occurs due to the same reason.
· Amount of water used for cloth wash, utensils & cooking, floor wash and bathroom wash remains almost the same for working day & holiday. This is because these things are done regularly by the same person (housemaid).
· Amount of water in bathing is greater on holiday than the regular working day. This is because on holiday members get extra time to take a long shower.
Figure 3.9: Greywater generation on both working day & holiday
On both days-working day and holiday, almost 60-70% of total water use is greywater.
Figure 3.10: Indoor Household Water Use in Both Working day & Holiday
Comparison with other countries