Greywater Reuse System At HTCKLhtckl.water.gov.my/wp-content/...grey-water-reuse.pdf · The chemical and physical quality of greywater compared with raw sewage is shown in Table 2.4

Greywater Reuse System At HTCKL

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1.0 INTRODUCTION

Grey water is non-industrial wastewater generated from domestic processes such as

washing dishes, laundry and bathing. It comprises 50-80% of residential wastewater. Grey water

is distinct from black water in the amount and composition of its chemical and biological

contaminants (from faeces or toxic chemicals). Therefore, greywater is the components of

domestic wastewater which have not originated from the toilet.

Grey water contented with pathogenic micro organism including bacteria, protozoa,

protein and viruses in concentration high enough to present a health risk. Grey water also

contains oils, fats, detergents, soaps, salts and particles which can impact on operational

performance of life of greywater irrigation system. Therefore, a clear understanding of the

potential health risk, operational performance and essential impacts that can be caused by

improper designed greywater treatment and level application system.

Currently concerns on sustainable water management has generated much interest in the

reuse or recycling of grey water, both domestically and for use in commercial irrigation. Grey

water system can benefit us in many ways; economically and also technically. Although this

system has not been widely implemented in Malaysia but it is becoming established as a way of

moving towards sustainable management of the resources and environment.

Greywater reuse system concept is still very new throughout our region. As in Europe

and North America, they even have their own rules and regulations by their Government

regarding the installation of greywater reuse system. Nevertheless, in Malaysia, the system has

been implemented in various places for example Kuching, Sarawak using the Ecological

Sanitation (ECOSAN) system. Besides that, the system can also be found at rural area such as an

island where there is not enough water supplies available to be distributed among the houses.

Greywater is equivalent to traditional wastewater in the form of centralised to the

decentralised approach in wastewater management. The motivations to treat wastewater in a

decentralised way are diverse. Indeed, the decentralised approach can give many benefits as

descended by Morel and Koottatep, (2003):

i) Does not require large and capital intensive sewer trunks


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ii) Broadens the variation of technological options

iii) Reduces the water requirements for waste transportation

iv) Is adaptable to different discharge requirements

v) Reduces the risks associated with system failure

vi) Increases wastewater reuse opportunities

vii) Allows incremental development and investment of the system

Therefore, the advantages of separate greywater treatment in decentralised systems are to

shorten and close the water cycle, to prevent water shortage and to save money. The cycling of

water occurs in a spatially limited area and the reuse of treated greywater takes place near the

location where water was used initially. The reuse of greywater prevention of water shortage as

precious and expensive water is saved. Greywater often contains valuable nutrients for gardening

and irrigation and as a consequence it is not necessary to buy expensive mineral fertiliser.

Another important fact is that people feel more responsible of their treatment system when it is

decentralised and may willing to pay more attention to the issue of greywater management

(Imhof, B. and Mühlemann, J., 2005). The objective of this report is to assist in the promotion of

acceptable long term greywater reuse practice and promote conservation of water quality.

Figure 1.1: Concept of a Greywater reuse system


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2.0 DEFINITION AND TERMINOLOGY OF GREYWATER

2.1 Definition of Greywater

There are several definitions for greywater in the literature. The biggest difference is

whether kitchen wastewater is perceived as greywater or not. Table 1.1 gives an overview on

definitions of greywater used in the literature (Imhof, B. and Mühlemann, J., 2005).

Table 2.1 : Definitions of Greywater Used in the Literature (Greywater treatment on

household level in developing countries) ( Imhof, B. and Mühlemann, J., 2005)

Definition Kitchen

Included References

Wastewater from baths, showers, hand basins, washing

machines and dishwashers, laundries and kitchen sinks. Yes (Ledin et al., 2001)

Wastewater without any input from toilets, which means it

corresponds to wastewater produced in bathtubs, showers,

hand basins, laundry machines and kitchen sinks, in

households.

Yes (Eriksson et al., 2002)

Wastewater from washing machines, washing bowls,

showers, bath tubes, cleaning containing mainly detergents No (Wilderer, 2003)

Wastewater without input from toilets (i.e. wastewater from

laundries, showers, bathtubs, hand basins and kitchen sinks). Yes (Ottoson and Stenstrom, 2003)

Graywater is defined as all wastewaters generated in the

household, excluding toilet wastes. It can come from the

sinks, showers, tubs, or washing machine of a home.

Yes (Casanova et al., 2001)

Greywater is defined as all wastewater from non-toilet

plumbing fixtures around the home. The use of kitchen

greywater is not recommended as a greywater source.

No (Christova Boal et al., 1996)

The domestic wastes from baths, showers, basins, laundries

and kitchens specifically excluding water closet and urinal

waste. Greywater does not normally contain human waste

unless laundry tubs or basins are used to rinse soiled

clothing or baby’s napkins.

Yes

(Queensland, 2002)

(Australian/ New Zealand

Standard AS/NZS 1547:

2000 “On-site domestic

wastewater management”)

Graywater is washing water from bathtubs, showers,

bathroom washbasins, clothes washing machines and

laundry tubs, kitchen sinks and dishwashers.

Yes (Del Porto and Steinfeld,

2000)

Greywater is wastewater which is not grossly contaminated

by faeces or urine, i.e. the wastewater arising from

plumbing fixtures not designed to receive human excrement

or discharges and includes bath, shower, hand basin, laundry

and kitchen discharges.

Yes (NSW Health, 2000)

Greywater is wastewater generated in the bathroom, laundry

and kitchen, and is therefore the components of wastewater

which have not originated from the toilet.

Yes (Greywatersafer.com, 2004)


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2.2 Terminology of Greywater

Several synonyms exist for the term of greywater. The following list gives an overview

on the expressions used. In this guideline the expression “Greywater” is used. Table 2.2 shows

the further subdivision of wastewater and their sources (Wilderer, 2003).

Table 2.2: Subdivision of Wastewater

Type Sources

Brown water Wastewater containing faeces

Yellow water Wastewater containing urine

Black water Wastewater containing both, faeces and urine

Grey water Wastewater from washing machines, washing bowls, showers, bath tubes,

cleaning containing mainly detergents

Green water Wastewater from kitchen sinks containing mainly food particles

Storm water Collected on roofs and driveways containing dust, hydrocarbons, abraded

materials from rubber and break, and heavy metals from metallic roofs

Wastewater from kitchen sinks and dish washing is sometimes excluded from greywater

sources because of the potential to introduce microbial contaminants and/ or oils and greases that

would negatively impact the receiving environment (TOWTRC, 2003). But in most sources

kitchen wastewater is also contained in greywater. Table 2.3 shows the local water resources and

their relative quality (Barton & Argue, 2004).

Table 2.3: Local Water Resources and their Relative Quality (Barton & Argue, 2004)


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Study has been done by Imhof and Mühlemann, (2005) on the percentage of greywater

and blackwater by its sources based on household level in developing countries (refer Figure 2.2

below). The study shows that greywater is comprised of 69% source of wastewater from

bath/shower.

Water Source Relative Quality Treatment Required

Drinking water Reticulated water

distribution

High Quality Minimal – typically

chlorination and

filtration

Roof Runoff Primarily roof runoff Good Low level – typically

sedimentation occurs

within a rainwater tank

Stormwater

Runoff

Catchment runoff

(includes impervious

surfaces such as

roads, pavements,

etc)

Moderate Treatment to remove

litter and reduce

sediment and nutrient

loading.

‘Light’

Greywater

Shower, bath,

bathroom basins

Cleanest wastewater – low

pathogens and low organic

content

Moderate treatment to

reduce pathogens and

organic content

Greywater Laundry (basin and

washing machine)

Low quality – high organic

loading and highly variable

High level due to high

organic level and highly

variable quality

Blackwater Kitchen and toilet,

industrial wastewater

Lowest quality – high

levels of pathogens and

organics

Advanced treatment and

disinfection


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Figure 2.2: Percentage of Greywater and Blackwater by Source

(Source: Greywater treatment on household level in developing countries) (Imhof B. and

Mühlemann J., 2005)

Figure 2.3: Comparison of Greywater and Blackwater

(Source: Environmental Building News March/April, 1995)

The chemical and physical quality of greywater compared with raw sewage is shown in

Table 2.4. The high variability of the greywater quality is due to various factors such as source of

water, water use efficiencies of appliances and fixtures, individual habits, products used (soaps,

shampoos, detergents) and other site specific characteristics.

34%


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Table 2.4: Comparison for chemical and physical quality of greywater and raw sewage

Jepperson and Solley (1994)

Parameter Unit Greywater Raw Sewage

Range Mean

Suspended Solids mg/L 45-330 115 100-500

Turbidity NTU 22->200 100 NA

BOD5 mg/L 90-290 160 100-500

Nitrite mg/L <0.1-0.8 0.3 1-10

Ammonia mg/L <1.0-25.4 5.3 10-30

Total Kjeldahl

Nitrogen

mg/L 2.1-31.5 12 20-80

Total Phosphorous mg/L 0.6-27.3 8 5-30

Sulfate mg/L 7.9-110 35 25-100

pH mg/L 6.6-8.7 7.5 6.5-8.5

Conductivity mS/cm 325-1140 600 300-800

Hardness (Ca & Mg) mg/L 15-55 45 200-700

Sodium mg/L 29-230 70 70-300

2.3 Benefits of Greywater Reuse System

The benefits of greywater can be described as follows:

a) Lower fresh water use

Grey water 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

evenly split between indoor and outdoor. All except toilet water could be recycled outdoors,

achieving the same result with significantly less water diverted from nature.

b) Less strain on septic tank or treatment plant

Grey water 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.

c) Highly effective purification


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Grey water 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.

d) Site unsuitable for a septic tank

For sites with slow soil percolation or other problems, a grey water system can be a partial or

complete substitute for a very costly, over-engineered system.

e) 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 the wastewater in the soil under the fruit trees definitely encourages the owner to

dump fewer toxic chemicals down the drain.

f) Groundwater recharge

Grey water application in excess of plant needs recharges groundwater.

g) Plant growth

Grey water enables a landscape to flourish where water may not otherwise be available to

support much plant growth.

h) 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 grey water helps to maintain the fertility

of the land.

i) Increased awareness of and sensitivity to natural cycles

Grey water use yields the satisfaction of taking responsibility for the wise husbandry of an

important resource.

3.0 CONCEPT OF GREYWATER REUSE SYSTEM

The characteristics of grey water vary regionally and over time. Three factors

significantly affect grey water compositions: water supply quality, the composition of the system

that transports both grey and drinking water and the activities in the house. Possibilities of reuse

for this fraction of wastewater have come into special focus. Treated grey water can be used for

many activities such as toilet flushing, garden watering and recreational irrigation. Usually

simple treatment system for the purpose of landscape irrigation, like sand/gravel filtration or


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settlement and flotation are operated to prevent clogging of the distributing system. A more

sophisticated design is needed, if the treated water is used “in-house”, e.g. for toilet flushing. A

disinfection step is added to remove microbial contaminants since the potential for human

contact is greatly increased in these applications (Lamine et. al., 2006).

Fangyue, et.al (2009) has proposed a non-potable urban grey water treatment and reuse

scheme. The reuses of the reclaimed grey water in urban areas are based on the grey water

characteristics and the proposed standards. He concluded in his study that all types of grey water

show good biodegradability in terms of the COD: BOD5 ratios. The bathroom and the laundry

grey water are deficient in both nitrogen and phosphorus. The kitchen grey water has a balanced

COD: N: P ratio. If grey water is intended to be treated through a biological process, it is

suggested that kitchen grey water shall be mixed with other streams to avoid the deficiency of

both macronutrients and trace nutrients. Due to the poor removal efficiencies of both organic

substances and surfactants, anaerobic processes are not recommended for the grey water

treatment. The aerobic biological processes, such as Rotating Biological Contactor (RBC) and

Sequencing Batch Reactors (SBR) can be applied for medium and high strength grey water

treatment. The combination of aerobic biological process with physical filtration and disinfection

is considered to be the most economical and feasible solution for grey water recycling. Finally,

Membrane Bio-Reactor (MBR) appears to be a very attractive solution for medium and high

strength grey water recycling, particularly in collective urban residential buildings serving more

than 500 inhabitants.

Dixon et al. (1999) has done a research to identify optimal recycling design as greater use

of grey water recycling is likely to depend on social, technical and economic factors. They have

developed a conceptual model for the combined use of grey water and rainwater for non-potable

domestic water uses in order to assess the potential gain in water saving efficiency from

increasing storage capacity. The model indicated that significant gains in water saving efficiency

could be obtained (up to 85%) with a modest storage capacity of 200 liters. However, the

findings of the study suggested that recycling systems in individual dwellings are unlikely to be

cost-effective.

Bakir (1999) has documented the concept of closed loop in water demand management.

The main idea is to match water quality with appropriate water uses. In other words, greywater


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may be allocated for appropriate uses, such as, irrigation, landscaping, toilet flushing, and

groundwater recharge. Every drop of water can be used at least twice before it is sent out of the

loop. After water is used, the generated wastewater is segregated according to the level and type

of contamination it contains. The wastewater streams are treated and the recycled water is kept in

the loop and used in appropriate applications.

In Malaysia, greywater reuse system has been implemented in several places such as in

Sebangkoi Country Resort, Sarikei, Sarawak using the Ecological Sanitation (ECOSAN) system

(Norway). The philosophy of Ecological Sanitation, also known as ECOSAN, is an alternative

sanitation technique based on the concept of human excreta and wastewater as a valuable

resource being developed by a number of European countries (Langergraber and Muelleger,

2005; Werner, 2006). Nutrients from human faeces and urine are recovered for the benefits of

agriculture. Such systems also ensure that water is used economically and is recycled in a safe

way to the greatest possible extent for purposes such as irrigation or groundwater recharge (Mah

D.Y.S. et. al, 2008).

Figure 3.2: Example of a greywater system in Sarikei, Sarawak using the ECOSAN system

(Image courtesy of Chemsain Engineering Sdn. Bhd.)

4.0 APPLICATION OF GREYWATER SYSTEM


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Grey water can be reused to benefit both man and nature, especially in urban area

especially in Kuala Lumpur where water thriftiness is becoming a major trend. Below are two

applications of grey water in Malaysian context, where they could be put into good use.

4.1 Irrigation

Grey water usually breaks down faster than black water due to its lower nitrogen and phosphorus

content. However, it must still be assumed that grey water may contain pathogens and

microorganisms that may harm humans. Thus grey water when applied in Malaysia should be

applied underground whenever possible to avoid humans coming into contact with potentially

dangerous microorganisms. There could be a danger of inhaling the water as an aerosol.

4.2 Indoor reuse

Recycled grey water from showers and bathtubs can be used for flushing toilets, which

potentially saves a lot of water because a lot of water is used when flushing the toilet. However,

greywater that has not been treated should not be used as flush-water because it will cause the

toilet fixture to smell and discolour, especially if left for more than one day.

In developed countries, greywater is also reused for a whole range of applications including:

i. Urinal and toilet flushing;

ii. Irrigation of lawns (college campuses, athletic fields, cemeteries, parks and golf courses,

domestic gardens);

iii. Washing of vehicles and windows;

iv. Fire protection;

v. Boiler feed water;

vi. Concrete production;

vii. Develop and preserve wetlands;

viii. Infiltrate into the ground; and

ix. Agriculture and viticulture reuse;

5.0 TYPE OF GREYWATER REUSE SYSTEM AVAILABLE


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5.1 Types of systems available

Greywater reuse systems vary significantly in their complexity and size from small

systems with very simple treatment to large systems with complex treatment processes.

However, most have common features such as:

i. some sort of treatment facility;

ii. a tank for storing the treated water;

iii. a pump; and

iv. a distribution system for transporting the treated water to where it is needed.

All systems that store greywater have to incorporate some level of treatment, as untreated

greywater deteriorates rapidly in storage. This rapid deterioration occurs because greywater is

often warm and rich in organic matter such as skin particles, hair and soaps/detergents. This

warm, nutrient-rich water provides ideal conditions for bacteria to multiply, resulting in odour

problems and poor water quality. Greywater may also contain harmful bacteria, which could

present a health risk without adequate water treatment or with inappropriate use. The risk of

inappropriate use is higher where children have access to the water. Greywater systems can be

grouped according to the type of treatment they use. The following are the obtained description

of each type of greywater system.

(a) Type 1: Direct reuse systems (no treatment)

It is possible to use greywater without any treatment provided that the water is not stored for

long before use. For example, once bath water has cooled, it can be used directly to water the

garden. Very simple devices are required to make this practical. One perfect example of this

system is the ‘WaterGreen’ done by Droughtbuster Ltd from United Kingdom which is

essentially a hose pipe with a small hand pump to create a siphon. This allows cooled bath water

to be taken directly from the bath and sent through the hose to the garden (usually via an open

window). Using greywater in this way may not be for everyone, but it does provide an

inexpensive and easy way of saving water while avoiding the issues that arise when greywater is

stored for any length of time. It is particularly useful for keen gardeners when water use

restrictions are in place. Experts usually advise that greywater should not be used on fruit or

vegetable crops (used for garden irrigation).


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(b) Type 2: Short retention systems

These systems take wastewater from the bath or shower and apply a very basic treatment

technique such as skimming debris off the surface and allowing particles to settle to the bottom

of the tank. An example of such a system is the ‘Ecoplay’ unit (United Kingdom), which aims to

avoid odour and water quality issues by treating the greywater to a basic standard and ensuring

the water is not stored for too long. If it is not used within a certain time, the stored treated water

is released and the system is topped up with mains water. However, potential water savings are

dependent on usage patterns. Using the simplest level of treatment makes these systems

relatively cheap to buy and run, while reducing the risk of equipment failure leading to expensive

repairs. Another benefit of these systems is that they can be located in the same room as the

source of greywater, thus reducing the need for expensive, dual-network plumbing. There are

some limitations for this type of system where it is limited to the domestic market (including

hotels) where it can be installed in a bathroom and the balance of shower use and toilet flushing

allows it to operate effectively. The system also suited to installation in newly built homes and

renovation projects, but is not recommended for retrofitting. The system’s reliability,

maintenance requirements and long-term savings are, as yet, unproven.

Figure 5.1: Ecoplay Greywater Harvesting System (CME Sanitary Systems Limited)

(http://www.ecoplay-systems.com)

(c) Type 3: Basic physical and chemical systems


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Some systems use a filter to remove debris from greywater prior to storage while chemical

disinfectants (e.g. chlorine or bromine) are used to stop bacterial growth during storage. The use

of disinfectant has an environmental impact as well as cost implications. Both need to be

considered in overall costs and benefits. A study by the Environment Agency of UK’s National

Water Demand Management Centre’s (NWDMC 2000) of this type of system reported:

A range of water savings from less than 6 to over 32 per cent of total water use;

Variable reliability;

Filters required regular cleaning to avoid blockages;

Odour problems due to either poor water quality or high levels of disinfectant;

Instances where the system had failed and switched to mains back-up with users unaware of

the failure.

Several other studies have looked at the water saving potential of these systems and have also

encountered similar reliability issues. For example, South Staffordshire Water installed and

monitored physical/chemical greywater systems in a block of flats and found them unreliable

(Environment Agency, United Kingdom, 2008). Some residents were initially happy with the

systems but, with time, residents identified problems such as odour, performance, noise and

quality of the water. These problems were worsen by difficulties in gaining access to the systems

in the flats for service and repair, and eventually led to their removal. The payback was estimated

at over 65 years which, in this case, was significantly longer than the life of the systems. This

project highlighted the technical and practical issues that can occur with the installation of basic

greywater systems. For example, access issues could have been avoided if a communal system

had been installed instead of individual systems in each flat.

A study by Thames Water in conjunction with Cranfield University monitored the

effectiveness of five individual household scale greywater systems between April 1999 and May

2000 (Hills et al. 2002). The systems studied were very similar to those described in the earlier

Environment Agency report (NWDMC 2000). The systems used basic filtration and chemical

disinfection (bromine) to treat the greywater. Of the five houses investigated, one produced no

data due to monitoring difficulties and another was often left unoccupied. This left three systems

producing representative data, with savings of 9–21 per cent of total consumption. Systems were

unreliable and users often did not know when the systems had failed. Problems were identified

during regular, routine system checks by project staff and faults fixed quickly. But even with this


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support in place, the poor reliability of the systems meant the actual savings realised were

significantly below the expected 40 per cent of total domestic consumption.

(d) Type 4: Biological systems

Biological systems vary in their complexity and form, but the concept is the same: bacteria are

used to remove organic material (contamination) from wastewater. The process uses the same

principles employed at sewage treatment works. Oxygen is introduced to wastewater to allow the

bacteria to ‘digest’ the organic contamination. Different systems supply oxygen in different

ways; some use pumps to draw air through the water in storage tanks while others use plants to

aerate the water. In nature, reeds thrive in waterlogged conditions by transferring oxygen to their

roots. Biological systems generally use reed beds to add oxygen to wastewater and allow

naturally occurring bacteria to remove organic matter. Wastewater can be passed through the

soil/gravel in which the reeds are growing and the bacteria fed by oxygen from the reeds and

nutrients from the wastewater decompose the waste. Reed beds are an established method for

treating wastewater/sewage and can also be used to treat greywater.

Figure 5.2 : An example of Biological Greywater Reuse System (Green Roof Water

Recycling System –GROW)

(http://www.ncsu.edu/kenan/ncsi/pdf/ARO_Water1_Garland.pdf)

(e) Type 5: Bio-mechanical systems

The most advanced domestic greywater treatment systems use a combination of biological and

physical treatment. An example of such a system is the ‘AquaCycle® 900’.10 This system was

developed in Germany, where mains water is more expensive than in the UK (Ofwat, 2005) and

where greywater systems are more common. The ‘AquaCycle® 900’ is a substantial system

about the size of a large fridge, which means it needs to be installed in a basement or garage. It is

best installed during construction and is not suited for retrofitting into existing buildings due to


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cost and other practical difficulties. The AquaCycle® 900 is an ‘all-in-one’ unit which treats and

stores water in three enclosed tanks. Greywater is filtered through self-cleaning filters as it flows

into the storage unit. Organic matter is removed by microbial cultures formed on rubber chips.

Solid material is allowed to settle to the bottom of the tank and is removed automatically. The

system encourages bacterial activity by bubbling oxygen through the water. The final stage of

the system is UV disinfection to remove any remaining bacteria. This process claims to produce

treated water that meets EU bathing water standards. Combining physical and biological

treatment generally produces the highest quality water, but it also uses a significant amount of

energy, is expensive to purchase and operate, while the maintenance costs for this sytem are

uncertain. This high level of water quality may not be required if the use of treated greywater is

restricted in an individual property to toilet flushing. But where stored greywater is treated to a

high standard, there is potential for its use in other applications such as vehicle washing. A high

standard of water quality may also be required in communal systems to overcome both real and

perceived risks associated with the treated water.

Figure 5.3 : Diagram of the AquaCycle® 900 (Freewater UK Ltd)

(http://www.freewateruk.co.uk/greywater-III.htm)

6.0 DESIGN CONSIDERATIONS


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The design must allow the user to direct the greywater to irrigation, landscape, disposal

field or the sewer.

The direction control of the greywater must be clearly labeled and easily accessible by

the user.

No potable makeup water.

No pumps.

No spray irrigation of greywater (i.e., no sprinklers).

The system must not affect other building, plumbing, electrical or mechanical

components including structural features, egress, fire-life safety, sanitation, potable water

supply piping or accessibility.

The greywater must be contained on the site where it is generated.

Greywater must be directed and contained within an irrigation or disposal field.

Greywater must NOT be used to irrigate root crops or edible parts of food crops that

touch the soil.

Ponding and runoff are prohibited.

6.1 DESIGN OPTION AND PROCEDURE

6.1.1 Design Standard Available

Basically, there is no specific design standard for the design of greywater reuse system. For this

project, two (2) different standards used which are:

1. WSUD Technical guidelines: Peel Harvey Coastal standard from Australia. The standard

is to determine the sizing of irrigation area and also the sizing of greywater tanks.

2. Design Option Based On Soakway Infiltration and Conveyance System

6.1.2 Design Option Based On Peel-Harvey Coastal Catchment Water Sensitive Urban

Design Technical Guidelines


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The design option standard is based on one of the WSUD standards in Australia. The design

procedure requires 4 steps:

Figure 6.1: Flow diagram of the greywater calculation steps

Step 1: Calculate the Greywater Volumes

Greywater flow is based on the number of bedrooms rather than the actual number of occupants

in a dwelling, because the number of bedrooms will remain constant over time. Daily domestic

greywater volumes are listed in Table 6.1.

Table 6.1: Daily domestic greywater generation rates

(Peel-Harvey Coastal Catchment WSUD Technical Guidelines)

Number

of

Bedrooms

Domestic Greywater Volumes (Litres per Day)

Greywater Source Total Greywater Flow

Kitchen* Laundry Bathroom

2 or less 72 126 153 351

3 96 168 204 468

4 120 210 255 585

5 or more 144 252 306 702

Notes: Figures based on an allocation of 117 L greywater flow per person per day, comprised of 24 L for kitchen,

42 L for laundry and 51 L for bathroom.

* A 1,800L sedimentation tank is required for Greywater systems that include kitchen greywater systems that

include kitchen greywater.

Step 2: Sizing the Greywater Tanks


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Greywater systems treat all greywater streams (i.e. kitchen, bathroom and laundry) must have a

sedimentation tank that has a minimum volume of 1,800 L, unless otherwise approved by the

Executive Director, Public Health. Greywater systems that only treat bathroom and/or laundry

greywater via sedimentation tank must be designed to provide at least 24 hour combined

retention for the daily flow of greywater (i.e. double the daily flow) or higher if a spa bath is

connected.

Step 3: Sizing the Irrigation Areas

Greywater irrigation systems are sized on whether they use sub-soil trench irrigation or

drip/spray methods. Systems are sized on the capability of the soil to receive the greywater (i.e.

the loading infiltration rate (LIR)) and the estimated daily greywater flow. The permeability of

the soil is to be determined in accordance with the requirements of the Health (Treatment of

Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974.

(a) Subsoil Trench Irrigation Sizing

The size of the greywater irrigation trench is calculated using the following equation:

L = V / (LIR x A) Eq. 5.2

where,

L = length of trench in meters

V = daily greywater volume in litres per day (L/day)

LIR = Loading Infiltration Rate (L/m2/day). The infiltration rates for greywater flow are

determined on the soil type.

A = surface area of the trench in m2 (i.e. the sides below the invert of the distribution pipe

and base of the trench per linear meter)

The LIR can be higher, if the system has a diverter and alternating trenches (i.e. two trenches that

have a diverter box that can change the flow of greywater, allowing one of the trenches to be

turned off at any time). By diverting the flow of greywater or shutting off the irrigation area, the

irrigation area can rest and dry out. This rejuvenates the soil’s ability to receive greywater. If the

system has no diverter and does not have alternative trenches, a lower infiltration rate must be

used.

(b) Drip or Spray Irrigation Sizing


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The required irrigation area size should be calculated on the basis of 10 L/m2/day in sand and

gravel/loam or for other soils in accordance with AS 1547:2000, Onsite Domestic Wastewater

Management.

Table 6.2: Standard Greywater Loading Infiltration Rates

Time for Water

to Fall

25 mm**

(minutes)

Soil Texture

Loading Infilration Rate (L/m2/day)

System with diverter

and/or alternating

trenches

Systems with no

diverter and non-

alternating trenches

1 to 5 Sand 30 15

5 to 60 Loams or gravels 20 10

> 60 Impervious clays As approved by the Executive Director Public

Health.

A procedure measures the soil permeability by recording the time taken for water in a 300 mm x

300 mm hole to fall 25 mm.

Step 4: Reduced sizing allowance for dripper system

The location of the greywater system must be located to avoid damage to buildings, structure and

adjoining properties. Table 5.7 below showing the minimum setback distances for the location of

the greywater system to be installed.

Table 6.3 : Minimum setback distances for greywater systems

6.2 Design Option Based On Soakway Infiltration and Conveyance System

Item Minimum Distances from

Drip Irrigation Area (m)

Closed fence boundaries 0.3

Open boundaries (ie. Open fence or no fence) 0.5

Buildings 0.5

Sub-soil drains 3.0

Bores (private 30

Paths, drives. Carports etc. 0.3

Public water supply production bores 100

Wetlands and water dependent ecosystems 100


Page 22 - 35

The final design option is based on the Soakway Infiltration and Conveyance System.

This standard has also been implemented for dwelling units Kampong Nelayan in Pulau

Perhentian, Daerah Besut, Terengganu Darul Iman.

Data Required

DATA :

Average daily flowrate Qav = 2 m3/d

Peak factor f = 1

Influent BOD3 B = 80 mg/l

Influent suspended solids S = 100 mg/l

Ammonical Nitrogen NH = 10 mg/l

COD COD = NA mg/l

Oil & Grease O&G = 10 mg/l

POLLUTANT LOADING:

Hydraulic

Average flow rate per day, Qav = 2 m3/d

Peak flow rate per day, Qpeak = f * Qav

2 m3/day

Suspended Solid (SS),

Average flow rate per day, Qav = 2 m3/d

Total suspended solids, Qav * S = 0.23 kg/day

5 Day Biological Oxygen Demand (BOD5)

Average flow rate per day, Qav = 2 m3/day

Total BOD5, Qav * B = 0.18 kg/day

Chemical Oxygen Demand (COD)

Average flow rate per day, Qav = N.A. m3/day

Total COD, Qav * COD = N.A. kg/day

Ammonical Nitrogen (NH3N)


Page 23 - 35


Total NH3-N, Qav * NH3N = 0.02 kg/day

Fat, Oil & Grease FOG


Total FOG, Qav * OG = 0.02 kg/day

7.0 DESIGN EXAMPLES

7.1 Case Study at HTC

The example of the greywater reuse system calculation is based on the proposed design of the

system constructed at Humid Tropic Centre (HTC) as Figure 7.0 shows. The proposal is to

collect greywater from various sources e.g. washing machine, shower and also kitchen sink.

Figure 7.0 : Greywater Reuse System at HTC Kuala Lumpur

The infiltration soakway and conveyance pipe system are natural filtration system. The

wastewater from the pump sump is pumped into a series of natural filtration process involving

biofilter material and a subsurface constructed wetland.


Page 24 - 35

Several criteria have been taken into considerations including:

The treatment system must consider water quality from outfall falls into Class II.

Operation and maintenance cost must be as minimal as possible.

The system must have the ability to sludge naturally.

Based on the above criteria, it has been proposed that the greywater reuse system to be designed

to have the components as listed below:

i. Trash screen

ii. Compartment for sedimentation process to occur.

iii. Filtration unit using granular activated carbon.

iv. Compartment for anaerobic process to occur.

v. BOD5 treatment through attached growth system.

vi. Infiltrated stone soakway and sand filtration/perforated pipe for infiltration process to

occur before goes to final outlet to treat nutrients like nitrogen and phosphorus.

7.2 Design Example of Infiltration Soakways and Conveyance Pipe

The soakway is assumed to be approximately 1.5m above the seasonally high water table and

they will be filled with 50mm clean stone. Each trench will be lined with non-woven filter

cloth to prevent clogging of the stone. The appropriate bottom area of each trench is calculated

based on the following equation:-

1.0 Infiltration Trench Bottom Area

A = P x n x t

where :

V = 2 m3 (Volume to be infiltrated)

P = 50 mm/h (percolation rate of surrounding

native soil)

n = 0.4 (porosity for clear stone)

t = 24 h (retention time)

Hence:

A = 4.17 m2

Adopt : 2 soakway trenches and each has an area of 4.5 m2

Eq: 5.3


Page 25 - 35

Length, L = 3.0 m

Width, W = 1.5 m

2.0 The maximum allowable soakway pit depth = P x T

where:

P = 50 mm(minimum percolation rate)

T = 24 h (drawdown time)

Hence

Depth, D = 1200 mm

3.0 Amount of storage volume available within the soakways

V = LWD x n x f

where:

L = 6 m (Total length of soakway)

D = 1200 mm (depth)

W = 2.1 m

n = 0.4 (void space)

f = 0.75 (longevity factor)

Hence:

V = 4.536 m3

4.0 Conveyance Controls

a. Outflow from soakways

Q = f x (P/3600000)x (2LD+2WD+LW)xn

where:


P = 50 mm/h (percolation rate)

L = 6 m (length of soakway)

W = 1.5 m (width of soakway)

D = 1.2 m (depth)

n = 0.4

Hence: Discharge from soakways

Q = 0.00011 m3/s

b. Conveyance pipe: Pervious Pipe System (use 150mm diameter pipe)

Eq: 5.4

Eq: 5.5

Eq: 5.6


Page 26 - 35

Adopt 50 - 12mm perforations per metre pipe for conveyance

Equation: Perforated pipe exfiltration

Qef = (15A-0.06S+0.33)Qinf

where:

Qinf = flow in pipe

S = 0.5 % (slope of pipe)

A = 0.006 m2/m ( area of perforation/m length of pipe)

Table 7.1: Head versus Exfiltration

Depth of water in

pipe (mm)

Flow in pipe (m3/s)

(Qinf)

Exfiltration

Flow (m3/s)

(Qef)

0.00 0 0

0.025 0.0005 0.000195

0.05 0.0015 0.000585

0.075 0.003 0.00117

The 150mm dia water pipe adopted is OK

c. Volume available within the perforated pipe bedding

V = LWD x n x f

where:

L = 6 (Total length of perforated pipe)

D = 1200 mm (depth of stone)

W = 2.1 m (with of stone trench)

n = 0.4 (void space)


Hence:

V = 4.536 m3

5.0 Summary

a. The infiltrated soakways storage volume is 4.54m3

b. The pervious discharge pipe conveyance provide additional volume 4.54m3

The value obtained is a design figure which the system can handle where maximum

concentration is taken as consideration of the value although the kitchen greywater will have a

Eq: 5.7

Eq: 5.8


Page 27 - 35

BOD, TSS and Oil and Grease concentration much lower than the stated value. The sizing of the

irrigation area varies with the area that will be used on different purposes eg. car wash and plant

irrigation.

8.0 MAINTENANCE REQUIREMENTS

Adequate maintenance of wastewater treatment and reuse schemes is important to ensure

that the scheme continues to meet its design objectives in the long-term and does not present

public health or environmental risks. Each wastewater treatment system will have its own

maintenance requirements with manufacturers and suppliers able to provide relevant

maintenance regimes. A risk management plan is also required.

Adequate provision for downtime, such as scheduled maintenance, should be accounted

for. As example, the greywater plumbing should be connected to the mains sewer, enabling

immediate diversion and greywater disposal and provision for drinking (or mains) water to be

temporarily used for toilet flushing. All maintenance should be specified in a maintenance plan

(and associated maintenance inspection forms) to be developed as part of the design procedure.

Maintenance personnel and asset managers (or the building owner) will use this plan to ensure

the wastewater reuse scheme continues to function as designed. The recommended maintenance

is shown in Table 8.0.

The maintenance plans and forms should address the following:

Inspection frequency;

Maintenance frequency;

Data collection/storage requirements (i.e. during inspections);

Detailed clean-out procedures including:

Equipment needs

Maintenance techniques

Occupational health and safety

Public safety

Environmental management considerations


Page 28 - 35

Disposal requirements (of material removed)

Access issues

Stakeholder notification requirements

Data collection requirements (if any)

Design details.

Table 8.0 : Recommended Maintenance Schedule for Greywater Reuse System

(Source: Department of Energy Utilities and Sustainability NSW, 2007)

Greywater Diversion

Device Component Maintenance Required Frequency

Filter

Clean filter

- filter should be removed and

cleaned, removing physical

contaminants

Weekly

Replace filter

As recommended by

manufacturer or as

required (usually every 6

– 12 months)

Surge tank Clean out sludge from surge tank Every 6 months

Subsurface irrigation

distribution system

Check that water is dispersing

- regularly monitor soil to

ensure all areas are wet after

an irrigation period

Weekly

Soil condition

Check that soil is healthy.

Signs of unhealthy soil include:

(a) Damp and boggy ground

hours after irrigation

(b) Surface ponding and runoff

of irrigated water

(c) Poor vegetation growth

(d) Unusual odours

(e) Clumping of soil

(f) Fine sheet of clay covering

surface

Monthly


Page 29 - 35

8.1 OPERATION & MAINTENANCE AND LANDSCAPING

Table 8.1 shows the Operation & Maintenance Regulation and Checklist prepared for greywater

system.

Table 8.1 : Operation & Maintenance Regulation and Checklist

Operation and Maintenance Checklist

Avoid stagnant water—dig a little below the greywater outlets: is the soil

anaerobic (black, or with bad smell)?

Y / N

Are there new plant roots? Y / N

Are the plants happy? Y / N

Are there adequate plants to use the greywater? Y / N

Is the greywater controlled? Y / N

Is the greywater well-distributed for irrigation purpose? Y / N

9.0 TYPICAL DRAWING FOR GREYWATER REUSE SYSTEM

9.1 Greywater Reuse System Layout Plan and Cross Section

The greywater reuse system was designed to have the components as follows:

i. Trash screen

ii. Component for sedimentation process to occur

iii. Filtration unit using granular activated carbon

iv. Component for anaerobic process to occur.

v. BOD5 treatment through attached growth system.

vi. Infiltrated stone soakway and sand filtration/ perforated pipe for infiltration process.

The typical greywater reuse system layout plan and cross section is shown in Figure 9.1 and

Figure 9.2.


Page 30 - 35

Figure 9.1: Typical Drawing of Greywater Reuse System Layout Plan and Section B-B

Figure 9.2: Typical Drawing of Greywater Reuse System Cross Section

10.0 CONCLUSION


Page 31 - 35

Grey water treatment system in Malaysia should adopt the concept of using water that is

'fit for purpose'. In practice this means using high quality drinking water for drinking and other

personal uses, but not necessarily for purposes where alternative water sources can be safely

used, such as toilet flushing, garden watering, fire protection, washing vehicles and crop

irrigation.

Grey water can contain disease-causing microorganisms and other contaminants, its reuse

can carry health and environmental risks. Therefore care must be taken to ensure that untreated

grey water is used in a safe and controlled manner, or that best grey water treatment system in

Malaysia should be carried out to an appropriate level before use. Therefore, one of the

objectives of this study is to develop a guidance note based on local experience describing the

appropriate uses for grey water that has been treated to different degrees. Hence, it is hope that

the grey water system implemented in the study area will be an example of local grey water

system for individual building at lot scale in urban areas.

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Documents

Greywater Reuse System At HTCKLhtckl.water.gov.my/wp-content/...grey-water-reuse.pdf · The chemical and physical quality of greywater compared with raw sewage is shown in Table 2.4