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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
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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)
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Average flow rate per day, Qav = 2 m3/day
Total NH3-N, Qav * NH3N = 0.02 kg/day
Fat, Oil & Grease FOG
Average flow rate per day, Qav = 2 m3/day
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.
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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
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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:
f = 0.75 (longevity factor)
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
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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)
f = 0.75 (longevity factor)
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
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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
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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
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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.
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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
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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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