Impact And Design Of Water Recycle Systems In Cities

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 1

Impact and Design of Water Recycle Systems in Cities

Name

Institution

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 2

Contents

INTRODUCTION .......................................................................................................................... 3

1.0 Introduction ........................................................................................................................... 3

1.1 Background of the study ....................................................................................................... 3

1.2 Introduction to Milton Keynes UK Water Supply System ................................................... 6

1.3 Aims and Objectives ............................................................................................................. 7

LITERATURE REVIEW ............................................................................................................... 8

2.0 Introduction ........................................................................................................................... 8

2.1 The categories of grey water ................................................................................................. 8

2.2 The characteristics of grey water .......................................................................................... 9

2.3 Grey water treatment technologies ...................................................................................... 13

METHODOLOGY ....................................................................................................................... 18

3.0 Research on the Existing water recycling systems.............................................................. 18

3.1 Design Project ..................................................................................................................... 19

3.2 The Design Process ............................................................................................................. 20

Results and Discussion ................................................................................................................. 24

Conclusion and Recommendations ............................................................................................... 26

References ..................................................................................................................................... 36

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 3

INTRODUCTION

1.0 Introduction

The section herein gives a brief account of the objectives, background information and a

discussion of the research problems. The section provides foundational information about the

topic, statement of the objectives, research questions and the description of the importance and

the limitations of the study.

1.1 Background of the study

The high population growth across various parts of the world has to lead to various

strains on the environment, especially water and other resources. The high populations mainly in

the urban centres as well as some rural areas have been associated with acute water shortage

(Asano et al., 2007). Water scarcity is a real global issue that is occasioned by the high

population and the rapid industrial growth that has been taking place in past years. The water

scarcity across the globe can also be associated with the climate change which has resulted in

changes in the weather patterns. A report filed by the United Nations indicated that about forty

percent of the total world populations are affected by the water scarcity, and the situation is

expected to continue if stringent measures will not be taken to promote sustainable use of water.

The prolonged droughts resulting from the changing climatic patterns have also worsened

the situation leading to serious water scarcity in some parts of the world (Asano et al., 2007). The

prolonged droughts have resulted in the drying up of rivers and other sources of water. As a

result of the shortage, many countries have resorted to greywater recycling to increase the supply

of water. Recycling grey water is considered as one of the most effective ways of providing an

alternative source of water. According to Jimenez & Asano (2008), the Sustainable Development

Goals insists and recommends water treatment as one of the way of improving sustainable water

supply and countries such as the United States, United Kingdom, Japan and Germany have

embraced the water recycling culture.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 4

Population growth is considered as the primary driving factor of the demand for water.

The need for water is expected to increase at the same rate as that of the population (Schäfer &

Escobar, 2009). Therefore, the demand for clean water is likely to increase by at least thirty-

percent between the year 2000 and 2025 (Schäfer & Escobar, 2009). Out of the countries that

had suffered from a water shortage as of the year 2006, 33 percent of them were from Sub-

Saharan Africa. Various countries in the Sub-Saharan region have experienced severe growth in

population and industrial advancement which raises the question whether such nations will be

able to have enough water to sustain economic, social and environmental needs (Schäfer &

Escobar, 2009).

The need for clean water is expected to escalate as a result of the industrial growth and

the need for manufacturing and irrigation to sustain the ever-growing global population. Since

manufacturing companies and industries requires access to affordable, reliable and quality water,

recycling of water will offer a great opportunity for the enterprises to be able to sustain their

operations and increase the profitability (Wang et al., 2010). Therefore, most companies across

the world have switched to sustainable water management practices which promote water

recycling and reuse. Recycled water is widely accepted for use in many parts of the world after

the application of various treatments and can be used in various industrial processes such as

cooling, material washing, and toilet flushing and landscape irrigation. Toilet flushing is

considered as one of the main uses of water in the households and offices, and it accounts for the

largest percentage of the total water used in the house (Wang et al., 2010). Therefore, recycled

water will provide a suitable alternative for flushing the toilet and reducing the amount of clean

water required in the house.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 5

In the United States, for instance, the Stone Brewery launched beer made using recycled

water in a toilet tap program which is a project that is still under the experimental stage (Wang et

al., 2010). Another important example of a water recycling project can be found in Australia

where the Castlemaine Perkins Ltd, a beer, producer at the Milton brewery adopted water

recycling method. The company adopted the water recycling plant to comply with the

requirements put across by the Queensland Water Commission water regulations (Wang et al.,

2010). The plant consisted of water recycling and treatment system with biological treatment

technology, reverse osmosis chamber and the membrane system. The wastewater treatment

system reduces the amount of salt in the water and also disinfects the unit with ultraviolet light.

Apart from the industrial demand for water, the domestic users also require thousands of

water gallons for various uses including washing, agriculture among others. For instance, in

2005, the domestic public-supply of water per capita use accounted for about 95 gallons of water

per day (Hollender et al., 2009). A report on water usage in Florida also showed that every

person in Florida uses about 100 gallons of water every day (Hollender et al., 2009). Most of the

wastewater ends up in the drainage areas and finally get infiltrated into the ground. Therefore, if

the amount of wastewater getting into the ground is not controlled, the amount quality of the

groundwater in Florida may also be compromised. Proper handling and treatment of this

wastewater, disposal or reuse approaches can be used to protect Florida’s groundwater by

ensuring that no excess wastewater is getting to the ground through infiltration.

Reusing or recycling the wastewater from the households in industries will help in

promoting sustainable water usage and also help in reducing the shortage of water in various

parts of the world. In Florida, the reclaimed water is used for various purposes including fire

protection, irrigation and crop irrigation, toilet flushing and various industrial uses (Siripong and

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 6

Rittmann, 2007). Water recycling and reuse is an essential topic in the field of civil and

environmental engineering as it is among the main ways in which sustainable water usage can be

achieved. Big cities and urban areas should focus on water recycling methods to ensure that they

reclaim the large volumes of water coming from the residential and industrial areas so that they

can provide a continuous supply of water (Siripong and Rittmann, 2007). The urban places

should be on the spot on this topic due to the high populations and the high demand for water in

cities and towns. The high demand is also associated with the production of large amounts of

waste. Therefore, the report herein looks at the impact of recycled and reuse of water in cities.

The paper also looks at the contribution of water recycling in improving the lives of people

within the city as well as reducing the environmental pollution problems by taking care of all the

wastewater.

1.2 Introduction to Milton Keynes UK Water Supply System

Milton Keynes is considered as one of the driest regions in the United Kingdom. Milton

Keynes is in the Anglian region which receives only about 600mm of rain every year (Smith,

2008). The amount of rain received by the Anglian region is a third less than the amount received

by the rest of England (Smith, 2008). The Anglian region is classified as a water-stressed region

by the Environment Agency. The city has grown in the recent years, and the population of the

region has been increasing which indicates that the demand for water is expected to go high

hence it is important to manage the Milton Keynes water supply systems more effectively. The

Milton Keynes, Newport Pagnell and Woburn fall within the Rutherford South water resource

planning zone. The Rutherford region is among the regions in the Anglian region that is expected

to be the most water-stressed area. The expected growth in water scarcity in the region is

associated with the increased population and housing and climate change that have affected the

general climate of the region as well as the water supply. Therefore, to sustain the demand and

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 7

prevent the occurrence of the scarcity, it is important to implement a water management plan to

increase the supply of water in the region. The management plan should focus on increasing the

supply, improving water efficiency and reducing the amount of leakage in the water supply

systems.

The water management plan adopted by the Rutherford south water resource zone is

consistent with the Anglian Water’s plans and strategies such as the Love Every Drop campaign

which was intended to increase the awareness of the population about the value of water in the

region. Many water management strategies have been adopted by the Milton Keynes water

management bodies to promote the awareness of the importance of water in the region. All the

strategies are meant to control the supply and demand of water in Milton Keynes to ensure that

the scarcity of water in the region is significantly reduced. The strategies are also meant to

communicate the benefits of sustainable water usage and consumption to the households and

industries. The report herein provides a design for a water recycling system for the Milton

Keynes water supply system to improve the amount of water supplied as well as to provide a

more sustainable way of handling wastewater from industries and households.

1.3 Aims and Objectives

The main objectives of this research include:

1. To analyze the impact of water recycling systems in cities

2. To design a water recycling system for the Milton Keynes Water Supply System

More Objectives

1. To assess the various grey water and waste water treatment methods used in water

recycling systems.

2. Design of a simple water recycling system for the Milton Keynes Water supply

system

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 8

3. To investigate the various technologies used in recycling water within cities

including their efficiency.

LITERATURE REVIEW

2.0 Introduction

The supply of freshwater in the world has become scarce hence increasing the attention

towards alternative sources of water. Water reuse has gained significant momentum on talks

about sustainable water resource management, urban planning and green economies (Asano et

al., 2007). Reusing grey water is an alternative source of water that can be exploited

continuously then treated for other non-potable uses. The use of grey water has increasingly been

considered as a fundamental component of national and local efforts to enhance food security,

adapt to climate change, reduce environmental pollutants and extend the supply of water

(Jimenez & Asano, 2008). The methods of greywater treatment vary depending on the conditions

of sites and the characteristics of the grey water. The design of the grey water treatment system

majorly depends on the quality of water, the quantity of water to be treated and the reuse

applications. A wide variety of greywater treatment technologies have been put into application

and examined hence producing effluents of different qualities. The study conducted reviewed the

characteristics of grey water as well as the different treatment technologies with the aim of

formulating a schematic recycling system of grey water designed particularly for restricted

agricultural irrigation. The issues tackled in the study include the characteristics of grey water,

the guidelines and the current treatment technologies performance.

2.1 The categories of grey water

Grey water is described as wastewater that comprises of water from baths, hand basins,

dishwashers, kitchen sinks, showers and washing machine (Schäfer & Escobar 2009). However,

greywater excludes streams from toilets. Some authors have also excluded kitchen waste waters

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 9

coming from other grey water streams. Another category of grey water is called light grey water

also known as low strength grey water, and it comprises of wastewater coming from the

bathroom with the inclusion of showers and tubs (Schäfer & Escobar 2009). The next category of

water is called the dark grey water also known as high strength grey water, and it contains more

contaminated wastes coming from dishwashers, laundry facilities and in some cases kitchen

sinks. Light grey water coming from bathrooms includes body care products, soap, body fats,

and traces of urine, shampoos, hair and lint. Light grey water coming from wash basins contains

toothpaste, shaving wastes, soaps, body care products and hair (Schäfer & Escobar 2009). Dark

grey water coming from laundry includes bleaches, paints, non-biodegradable wastes, soap, oils

and solvents. Dark greywater coming from kitchen sinks, on the contrary, contains high amounts

of oil, dishwashing detergents, food residues and fat.

2.2 The characteristics of grey water

Grey water quantity

The consumption of water majorly depends on resource availability and quality of life

standards (Ferraro and York, 2001). The quantity of grey water to be generated will also depend

on the total consumption of water, standards of living, population strictures such as age and

gender, water installations of a given population and the habits of the residents (Ferraro and

York, 2001). Therefore, the variations of grey water range from fifty percent to eighty percent of

the total volume of wastewater that is produced in different households. According to York et al.

(2002), the typical grey water volumes vary from ninety to one hundred and twenty l/p/d.

However, countries with low income experiencing chronic water shortages may have the volume

of grey water being as low as twenty to thirty l/p/d. The volume of grey water could also vary

depending on whether an area is on an urban or rural setting.

The quality of grey water

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 10

Grey water is generated from the living habits of various people which determine how

they use water as Marella (2009) notes. The characteristics of the grey water, therefore, greatly

varies and is influenced by the cultural and social behaviour of residents, the lifestyle of the

residents, the consumption amount of water and the availability of the water (Marella, 2009).

Greywater constitutes various ranges of suspended solids, organic matters, inorganic ions, E. coli

and heavy metals. Studies have observed that the levels of the mentioned pollutants in grey water

are higher in comparison to wastewater. An example is a BOD5 present in composite samples of

grey water collected from rural areas reaching 1400mgL-1, which is higher than the reported

concentration in concentrated wastewaters (Harivandi, 1982). Studies have shown that the

characteristics of light grey water and dark grey water vary as expected from seasonal and daily

fluctuations depending on quality and quantity of the specific grey water. The ranges of turbidity

suspended solids, and electrical conductivity of the dark grey water are 19-444NTU, 12-

315mgL-1 and 190-1830µS respectively (Harivandi, 1982). On the other hand, the ranges of

turbidity, suspended solids and electrical conductivity of a light grey water are 12.6-375 NTU,

29-505 mgL-1 and 14-921µS respectively. The high-end range of electrical conductivity is

experienced in countries experiencing water scarcity. The COD and BOD concentrations range

between 50-2568 mgL-1 and 48-1056 mgL-1 for the dark grey water (Pirbazari and Shorr, 1990).

Alternatively, the COD and BOD concentrations range between 55-633mgL-1 and 20-300mgL-1

for the light grey water (Pirbazari and Shorr, 1990).

Kitchen grey water normally contains dissolved food particles that are biodegradable

hence contributing to the BOD whereas the high concentration of COD in dark grey water is as a

result to detergents present in dishwashing liquids and laundry powders. In comparison to

bathroom grey water, laundry and kitchen grey water exhibit high organic and physical

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 11

pollutants (Pirbazari and Shorr, 1990). Research also shows that fewer microorganisms

contaminate laundry and bathroom greywater compared to kitchen grey water. Further studies

indicate that water coming from the kitchen constitutes 3-4 logs to faecal grey water loads that

may be as a result of large amounts of organic substances that are easily biodegradable in kitchen

grey water (Molof and Yun, 1992). Kitchen grey water could also be contaminated by coliforms

that are thermal-tolerant compared to other grey water streams. Guidelines provided by World

Health Organization refer to faecal contamination as the primary hazard of grey water.

Additionally, the high number of bacteria presents shows that human contact with grey

water could result in infections and illnesses. Faecal contamination originates from washing

clothes that are contaminated, washing raw meats and child care (Göbel et al., 2007). The

concentrations of nutrients are higher in dark grey water compared to light grey water because of

phosphates and kitchen grey water coming from laundry detergents. There are variations in

elemental concentrations depending on plumbing conditions and water quality prevailing in each

country (Göbel et al., 2007). Laundry detergents contain heavy metals such as Cu, Cr, Zn, Cd

and Pb hence making them unsuitable for any irrigation (Göbel et al., 2007). Biodegradability is

used to signify the abilities of different bacteria to decompose or digest organic matter present in

grey water by converting them to carbon dioxide and water.

According to Muga and Mihelcic (2008), biodegradability is an important concept to

consider because it determines how effective a biological treatment can work on grey water. All

kinds of grey water show good biodegradability features when it comes to COD: BOD5 ratios to

mean that almost half of the organic matter present in grey water can be biodegradable. To

achieve proficient aerobic biodegradation, the ratio of COD: N: P needs to be 100:20:1 (Muga

and Mihelcic, 2008). Greywater originating from the kitchen contains highest levels of

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 12

suspended solids, nitrogen, organic substance and turbidity. Conversely, kitchen greywater has

phosphorous and Nitrogen and hence has a COD: N: P ratio that aligns with the ratio suggested.

Further studies reveal that kitchen water excluded from grey water stream resulted to an average

COD: N: P ratio of 100:3.5:1.6 that means aerobic biological treatment cannot be effective

enough due to a deficit in nitrogen (Muga and Mihelcic, 2008). Laundry and bathroom grey

water is deficient in phosphorous and nitrogen due to urine and faeces exclusion. In exceptional

cases, mixed grey water and laundry greywater could be low in phosphorous when phosphorous

free detergents are used. To enhance the process of aerobic biological treatment nitrogen

nutrients should be added to the grey water. The latter could be achieved by allowing grey water

to be mixed with kitchen water.

Greywater reuse guidelines

Greywater that has been reclaimed needs to fulfil four reuse criteria that include hygienic

safety, environmental tolerance, economic feasibility and aesthetics (Cheremisinoff, 2001). The

different applications of reuse need different specifications on the qualities of water and hence

demanding different methods of treatment that vary from simple processes to advanced

processes. Standard grey water monitoring values vary depending on the country with few

guidelines designed for recycling grey water (Cheremisinoff, 2001). Majority of countries tend to

apply same standards of recycling grey water same to that of recycling municipal wastewaters.

However, countries such as United Kingdom, Japan, Australia, Jordan and Germany have

established specialised standards for the reuse of grey water (Cheremisinoff, 2001). The

differences observed between the reuse criteria replicate differences arising in applications,

social factors and need. The World Health Organization provided a publication on the guidelines

of greywater reuse that showed a significant shift in perception towards reuse of wastewater and

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 13

grey water. The set guidelines were based on Stockholm framework that combined risk

management and risk assessment to control diseases that are water related.

The guidelines outlined microbiological requirements without special considerations for

other chemical and physical parameters. Additionally, the parameters never paid attention to

water quality standards but focused on appropriate health protection measures that are essential

in achieving targets that are health based. World Health Organization refers to treatment as one

of the strategies used to reduce any risk that was associated with greywater instead of defining

water treatment as the best option for greywater reuse (Wang et al., 2010). The guidelines set by

the World Health Organization indicate measures on health protection like crop restriction,

hygienic food preparation and food handling practices as well as standards on health protection

like crop restriction, periods between water application and harvest being withheld as being the

key factors that lower risks associated with greywater without undergoing advanced treatment.

The main challenge faced in applying the guidelines include the lack of understanding and

cooperation of stakeholders in accessing and managing risks associated with any hazards (Wang

et al., 2010). Later, the World Health Organization developed safety planning methods on

sanitation as well as publishing them in manuals that enclosed the disposal and safe use of grey

water and wastewater among others.

2.3 Grey water treatment technologies

When greywater reuse is untreated, it can lead to health risks for both humans and the

environment. Therefore, it is important that the grey water is reused be treated to higher

standards. The main aim of the treatment process is to overcome aesthetic, technical and health

problems that could be caused by pathogens, solid or organic matter as well as meeting all the

reuse standards (Wang et al., 2010). Several studies have been conducted on how grey matter can

be treated using various technologies varying in performance and complexity. However, there is

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 14

a scarcity of the studies conducted to evaluate the appropriateness of the technologies used to

treat grey water and the cost-effective methods of treatment. The technologies that are used to

treat grey water are classified with basis on the principle of treatment and can be further divided

into chemical, biological and physical systems or a combination of the three. The technologies

are mostly preceded by three steps that include pre-treatment, main treatment and post-treatment.

To prevent subsequent treatments from clogging, pre-treatment options like filter bags, filters,

screens and septic tanks should be used to reduce particles amounts together with oil and grease.

Biological greywater treatment systems

Various biological treatment systems have been used in the treatment of grey water, and

they include Rotating Biological Contactor, Sequencing Batch Reactor, Membrane Bioreactors,

and Fluidized Bed Reactor and up flow Anaerobic Sludge Blanket (Hollender et al., 2009).

Biological systems are always preceded by coarse filtration stage of pre-treatment followed by

filtration or sedimentation to eliminate sludge or biosolids and the post-treatment stage of

disinfection where UV and chlorination are used to eliminate microorganisms. Aerobic

biological processes are the best in achieving excellent turbidity and organic removal rates

(Hollender et al., 2009). After the process of aerobic biological greywater treatment, the majority

of organic substances that are biodegradable are removed then odour problems, and re-growth of

microorganisms are consequently avoided hence making the greywater that has been treated

more stable for longer storage. Therefore, the grey water medium to high strength can best be

treated using biological processes.

MBR combines membrane filtration with biodegradation when separating solids and

liquids. The MBR is the best innovative technology for the treatment of greywater because it is

the exceptional technology that can be used to satisfactorily remove efficiencies of surfactants,

microbial contaminations and organic substances without needing disinfection and post-filtration

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 15

steps. MBR tends to be the most attractive technical solution for recycling grey water especially

in urban residential structures because it produces stable and excellent quality effluents have

high organic loading rates with the low excess production of sludge and compact structure.

Buildings exceeding thirty-seven stories should use MBR greywater treatment systems because

they are more economical and feasible. MBR greywater treatment serving more the five hundred

inhabitants has an estimated annual operating cost and capital dropping to 1.7€ per cubic metre.

The MBR operational and investment costs could be high hence less affordable to developing

countries.

RBC and FBR, on the other hand, are efficient to treat light grey water (Siripong and

Rittmann, 2007). When RBS and FBR are used to treat baths, washbasin and shower grey waters

the initial concentration of BOD was found to be less (Siripong and Rittmann, 2007). RBS

requires little maintenance with an increase in some stages. Also, RBC is efficient in removing

micropollutants and BOD in comparison to removing COD.

SBR has all the treatment processes occurring in a reactor tank hence making it a special

kind of activated sludge processing. SBR performs biological treatment, secondary clarification

and equalisation all in a single tank by use of a time-controlled sequence. SBR is one of the

technologies used to remove conventional parameters in the small communities (Siripong and

Rittmann, 2007). To achieve efficiency, the Hydraulic Retention Time requires thirty-six hours

that is impractical for applications in the real world.

Anaerobic treatment is not appropriate for recycling grey water because of poor removal

efficiencies of organic surfactants and substances (Hollender et al., 2009). On the other hand,

good treatment could be achieved when anaerobic treatment is used as a pre-treatment with a

combination of aerobic treatment in the presence of effluent disinfection and proper insulation.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 16

Aerobic treatment is better compared to anaerobic treatment when removing toxic effects in the

grey water despite anaerobic treatment being simple and of low cost.

Physical greywater treatment systems

The processes included in the physical greywater systems include filtration and

sedimentation. Filtration can be used as pre-treatment method before chemical and biological

treatments or as a post-treatment method before disinfection (Robinson et al., 2001). Filtration

being a pre-treatment method entails screen meshes, nylon sock type filtration, gravel filtration,

sand bed filtration, metal strainers and mulch tower system. Using physical greywater treatment

only is not efficient because there is no guarantee that the organics, surfactants and nutrients will

be adequately reduced apart from those situations where organic strengths are tremendously low

(Robinson et al., 2001). The efficiencies of the filtration method greatly depend on how the

particles of the grey matter pollutants are distributed and the porosity of the filters. Some of the

operational problems faced by the filters include cleaning frequencies (Robinson et al., 2001).

The widespread applications for treatment of grey water using membrane technologies can be

restricted by membrane fouling as well as the operations consequences and costs of maintenance

(Robinson et al., 2001). Raw grey water in storage and settling tanks when pre-treated can

mitigate any clogging problem related to the sand filters.

Chemical greywater treatment systems

The chemical greywater treatment system used include electrocoagulation, magnetic ion

exchange resin, advanced oxidation processes like photocatalysis and ozonation, coagulation and

flocculation, adsorption using natural zeolites and granular activated carbon and lastly powdered

activated carbon. The chemical systems are efficient for use in laundry grey water or light grey

water (Rout, 2013). The main advantage of chemical processes is that it can reduce the turbidity

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 17

of grey water as well as organic substances but unable to fulfil non-potable standards for reuse.

Studies have shown that chemical processes like coagulation followed by the disinfection or

filtration stage would likely reduce suspended organic substances, surfactants and solids in

greywater having the low strength to levels that can be accepted to meet non-potable urban

needs. Greywater with medium and high strengths, however, produces reclaimed water from

chemical processes that cannot meet the set standards for reuse unless the processes are joined

(Rout, 2013). Effluent coming from the chemical process can be polished using sand filtration or

treated further using a membrane stage of filtration to reach the non-potable standards of reuse.

Later, the effluents coming from the stage of sand filtration will then be disinfected to meet the

reuse standards that are not restricted. According to Rout (2013), the chemical treatment method

is best for single households having low strength systems of treatment as the variable because

flow and strength of greywater cannot be affected by the treatment performance.

The natural greywater treatment system

The treatment system uses natural filtration media and biological degradation such as

plants and soil (Rout, 2013). The treatment system can be used to treat dark grey water although

a disinfection stage is necessary when low pathogen effluents are required. Examples include

sand filters, vertical flow constructed wetlands, vertical flow filter, and horizontal flow

constructed a wetland and anaerobic filters. The above systems combine physical processes like

filtration with biological processes such as aerobic and anaerobic degradation. Constructed

wetlands are the most cost-effective and environmentally friendly technology that can be used to

treat and reuse grey water hence preferred in middle-income countries. However, they are not

suitable for urban areas because they require a large surface area (Rout, 2013). Researchers

observed that vertical flow reedbed removed pathogens better than horizontal reedbeds. To

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 18

improve the quality of the effluent, the system was to be operated with recirculation. Both

planted and unplanted VFCW showed good performances and its simplicity made it more

attractive. Mini wetlands that were constructed are constructed are more effective in treating grey

water sources as well as removing contaminants. The main goal of SSWL is to take full

advantage of functions of important ecological processes in a limited area.

METHODOLOGY

3.0 Research on the Existing water recycling systems

It is important to first define water recycling first before looking into the existing water

recycling technologies in existence today. The term can refer to the process of recovering useful

materials from the waste or the garbage (Siripong and Rittmann, 2007). It can also be defined as

the process of extracting a used item or object and reusing it. Recycling as the term is normally

associated with metals, plastics and other materials. However, water can also be recycled. Water

recycling, in this case, refers to the process of reusing the treated wastewater for other beneficial

uses such as irrigation, industrial usage, toilet flushing as well as replenishing the groundwater

(Siripong and Rittmann, 2007). Water recycling is an important undertaking as it offers both

resources and financial benefits. The quality of the recycled water can always be tailored to meet

the requirements of planned use by incorporating various types of treatments to ensure that it

meets the basic requirements of the planned use. For instance, water being recycled for drinking

purposes will require a higher quality level as compared to the water being recycled for the

landscape irrigation. Water treated to the stipulated standards has not been reported to have

caused any health problems.

Water can be recycled and reused onsite, for example in the case of an industrial facility

that recycles water for the cooling process. Another type of water that is recycled is the one

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 19

reclaimed from the city’s wastewater and sewer system to produce clean water that can be used

for various purposes within the neighbourhood.

The most common recyclable water is the grey water. The grey water, in this case, refers

to the reusable wastewater from the commercial bathroom sinks, bathtub shower drains,

residential and clothes washing equipment drainage systems. Gray water can also be used on site

for agricultural purposes through landscape irrigation.

3.1 Design Project

Milton Keynes is marked as an area that is likely to have water scarcity shortly as a result

of the population that continues to build up in the region. The demand for water is higher than

the supply which means that there should be other sustainable ways of using the water.

Therefore, the design project herein gives a preliminary design for an advanced wastewater

recycling system for Milton Keynes to increase the water supply for the region and also to

provide a better way of disposing of the wastewater. Therefore the main aim of the project is to

provide a conceptual design of an economical and effective wastewater treatment plant for

Milton Keynes water supply system.

The proposed plant will use the most sustainable and energy efficient concepts and keep

the maintenance and construction costs as low as possible to provide an efficient wastewater

recycling system. The objective of the project is to protect the aquifer from waste and

contaminated water and also minimise the environmental impacts on the surrounding

environment.

The design process includes taking into account the advantages and the limitations of the

different methods involved in the proposed recycling plant. The main design principles used in

this project include cost, efficiency, durability and ease of maintenance.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 20

3.2 The Design Process

Considering the initial capital that establishing the treatment plant will require, it is

essential to divide the project into three main phases. The first design phase will involve the

preliminary treatment process which will make the water safe for specific category of uses such

as landscape irrigation, toilet flushing and washing.

1. Preliminary Treatment – At this stage, the wastewater will be subjected to simple

treatment processes which involve the removal of debris, solid materials and other components

that are easily separable. The primary treatment will use a membrane bioreactor to remove the

influent wastewater.

2. Secondary Treatment – Secondary treatment involves the removal of the organic

components of the wastewater through biological processes. The secondary treatment will

involve the application of the biological methods to facilitate the conversion of the reduction of

the organic matters on the water to more stable forms. The secondary treatment involves the

application of aerobic and anaerobic processes. The secondary treatment will utilise a reverse

osmosis system to facilitate oxidation and the removal of organic compounds from the

wastewater.

3. Tertiary Treatment – is the last stage of the treatment process and it involves

purifying the treated effluent to levels that that are acceptable for discharge. It involves the

removal of specific pollutants such as nitrogen and phosphorus or other specific industrial

pollutants. The tertiary treatment will involve disinfection which will be performed using

ultraviolet technology.

The collection system for the water will be done through gravity where the wastewater will be

pumped through an 8-inch force main from one gravity fed section to the other.

Water Production Design

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 21

The water production facility is intended to supplement the water supplied in the Anglian

region by providing an alternative source of water in the area. The current production rate for

Milton Keynes may not meet the expected increase in demand for water in future.

The wastewater from the region will be recycled using a membrane bioreactor. A

membrane bioreactor was chosen because of its ability to provide the cleanest effluent water as

compared to other technologies.

For the proposed design, the membrane bioreactor will act as the primary method of

treatment for the influent wastewater. The secondary treatment method will utilise the reverse

osmosis membranes which will be used to ensure that the quality of the water living the plant

meets the acceptable standards. The water will be channelled to the plant using pipes connected

to the main sewer and distributed to the points of use using the effluent pipes living the main

storage tank at the facility.

The Following table shows the expected Plant Flows.

Flow – Liquid Treatment (MBR)

Average Daily Flow

201, 132 gpd

Maximum Daily Flow

403, 337 gpd

Flow – Solid Treatment

Average Daily Flow

4, 132 gpd

Maximum Daily Flow

8, 337 gpd

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 22

Flow – Liquid Treatment (RO)

Average Daily Flow

198, 542 gpd

Maximum Daily Flow

398, 367 gpd

Flow – 1.3% Lost to RO

Average Daily Flow

2, 590 gpd

Maximum Daily Flow

4,970 gpd

Portable Water Existing Plant

Average Daily Flow

148, 163 gpd

Maximum Daily Flow

297, 317 gpd

Choice of Equipment

There are various equipments that were designed to meet the requirements of each step of

the water recycling method. The following table shows the proposed equipment for the project.

Equipment

Description

Capacity

Pump

For pumping the water

into the treatment chamber

410,000 gpd

GE Water (Packaged

Plant)

Membrane bioreactor

for primary treatment

410, 000 gpd

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 23

Huber tech (Rotomat

Rotary Screw thickener)

Solid waste handling

500, 000 gpd

GE Water (Model

1225595, RO PRO-150-PRE)

Reverse osmosis

300, 000 gpd

Wedeco ITT

Ultra Violet treatment

for disinfection.

420,000 gpd

Cole Parmer

Chlorination

23.80 gpd

Membrane Bioreactor

The choice of the membrane bioreactor is based on the average and maximum flow per

day. The chosen membrane bioreactor meets the required flow requirements for the Milton

Keynes water supply system. The Zenon model was chosen due to its impressive contaminant

removal properties. The removal rates for the contaminants are as in the table below.

Fig. Zenome Model Removal Estimated (Muga and Mihelcic, 2008)

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 24

Reverse Osmosis Membranes

The reverse osmosis membrane is installed to improve the quality of the effluent water

from the bioreactor membrane. The reverse osmosis acts as a polishing method to clean the water

to meet the standards for drinking water and to make the water safe for consumption. The reverse

osmosis is used to treat the water to make it safe for consumption. The reverse osmosis plant was

obtained from the same manufacture packaged in the membrane bioreactor. The loss of water

during the reverse osmosis process was estimated at 1.3% due to the rejected contaminated

water.

Results and Discussion

According to findings of this research, there are various types of water recycling

technologies use in various municipalities, and each one of them has a different advantage and

disadvantage depending on the requirements of the system. For instance, the choice of a water

treatment technology mainly depends on the intended use of the water. For instance, if the water

is meant to be used for landscape irrigation or toilet flushing, then the primary treatment process

may be enough to treat the water. However, treating drinking water will require a series of

treatments including secondary and tertiary treatments to ensure that the final effluent water

meets the specified safety standards.

From the data obtained through the design, the Milton Keynes water supply system is

expected to have an additional 297, 317 gallons of clean and recycled water per day. The table

below shows the amount of water entering and leaving every section of the treatment plant as

well as the final amount of clean water leaving the facility.

Flow – Liquid Treatment (MBR)

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 25

Average Daily Flow

201, 132 gpd

Maximum Daily Flow

403, 337 gpd

Flow – Solid Treatment

Average Daily Flow

4, 132 gpd

Maximum Daily Flow

8, 337 gpd

Flow – Liquid Treatment (RO)

Average Daily Flow

198, 542 gpd

Maximum Daily Flow

398, 367 gpd

Flow – 1.3% Lost to RO

Average Daily Flow

2, 590 gpd

Maximum Daily Flow

4,970 gpd

Portable Water Existing Plant

Average Daily Flow

148, 163 gpd

Maximum Daily Flow

297, 317 gpd

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 26

The differences in the amounts of water entering and leaving each section of the

treatment plant can be associated with various factors which are specific to each treatment stage.

For instance, there are two sections of the recycling plant which require supplementary water

apart from the wastewater alone. The first section is the solid treatment which requires a supply

of water from a third party source. The reverse osmosis section also requires supplementary

water from a third party source. The 25% loss in the RO chamber is associated with the amount

of water rejected during the purification process.

From the design considerations and choice of equipment to meet the standards for clean

water, the quality of water coming out of the facility is represented in the following table.

Contaminant

Concentration

Turbidity

1NTU

TSS

5 mg/L

Nitrates

1 mg/L

E Coli

2.3 CFU/100ml

Conclusion and Recommendations

Primarily, the design consists of a network for collecting wastewater and directing it to

the treatment plant and then distributing it to the point of use. The treatment plant mainly

consists of the bioreactors and reverse osmosis systems which are responsible for recycling the

wastewater. The two treatment technologies operate using a membrane to reduce the footprint

size of the facility and also to produce clean and quality drinking water. The choice of each

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 27

component was based on its ability to handle the wide composition of the wastewater and to

provide the desired results as per the design specifications.

The plant will provide an alternative water source for the water-stressed Milton Keynes

region and also help in protecting the aquifer from excess infiltration of contaminated water. The

system will add a significant amount of water to the supply system and hence help in promoting

the Milton Keynes goal of water conservation.

However, the study herein is done on a basic level without considering the specific

design principles which will ensure that the system meets the required objectives. The design of

the water treatment system is based purely on secondary data and may not be feasible for

implementation. Therefore, future studies should consider collecting primary data on the water

status of Milton Keynes and the feasibility of implementing a wastewater recycling plant in the

region to provide an alternative source.

Design Project

Milton Keynes is marked as an area that is likely to have water scarcity shortly as a result

of the population that continues to build up in the region. The demand for water is higher than

the supply which means that there should be other sustainable ways of using the water.

Therefore, the design project herein gives a preliminary design for an advanced wastewater

recycling system for Milton Keynes to increase the water supply for the region and also to

provide a better way of disposing of the wastewater. Therefore the main aim of the project is to

provide a conceptual design of an economical and effective wastewater treatment plant for

Milton Keynes water supply system.

The proposed plant will use the most sustainable and energy efficient concepts and keep

the maintenance and construction costs as low as possible to provide an efficient wastewater

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 28

recycling system. The objective of the project is to protect the aquifer from waste and

contaminated water and also minimise the environmental impacts on the surrounding

environment.

The design process includes taking into account the advantages and the limitations of the

different methods involved in the proposed recycling plant. The main design principles used in

this project include cost, efficiency, durability and ease of maintenance.

The Design Process

Considering the initial capital that establishing the treatment plant will require, it is

essential to divide the project into three main phases. The first design phase will involve the

preliminary treatment process which will make the water safe for specific category of uses such

as landscape irrigation, toilet flushing and washing.

1. Preliminary Treatment – At this stage, the wastewater will be subjected to simple

treatment processes which involve the removal of debris, solid materials and other components

that are easily separable. The primary treatment will use a membrane bioreactor to remove the

influent wastewater.

2. Secondary Treatment – Secondary treatment involves the removal of the organic

components of the wastewater through biological processes. The secondary treatment will

involve the application of the biological methods to facilitate the conversion of the reduction of

the organic matters on the water to more stable forms. The secondary treatment involves the

application of aerobic and anaerobic processes. The secondary treatment will utilise a reverse

osmosis system to facilitate oxidation and the removal of organic compounds from the

wastewater.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 29

3. Tertiary Treatment – is the last stage of the treatment process and it involves

purifying the treated effluent to levels that that are acceptable for discharge. It involves the

removal of specific pollutants such as nitrogen and phosphorus or other specific industrial

pollutants. The tertiary treatment will involve disinfection which will be performed using

ultraviolet technology.

The collection system for the water will be done through gravity where the wastewater

will be pumped through an 8-inch force main from one gravity fed section to the other.

Water Production Design

The water production facility is intended to supplement the water supplied in the Anglian

region by providing an alternative source of water in the area. The current production rate for

Milton Keynes may not meet the expected increase in demand for water in future.

The wastewater from the region will be recycled using a membrane bioreactor. A

membrane bioreactor was chosen because of its ability to provide the cleanest effluent water as

compared to other technologies.

For the proposed design, the membrane bioreactor will act as the primary method of

treatment for the influent wastewater. The secondary treatment method will utilise the reverse

osmosis membranes which will be used to ensure that the quality of the water living the plant

meets the acceptable standards. The water will be channelled to the plant using pipes connected

to the main sewer and distributed to the points of use using the effluent pipes living the main

storage tank at the facility.

The Following table shows the expected Plant Flows.

Flow – Liquid Treatment (MBR)

Average Daily Flow

201, 132 gpd

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 30

Maximum Daily Flow

403, 337 gpd

Flow – Solid Treatment

Average Daily Flow

4, 132 gpd

Maximum Daily Flow

8, 337 gpd

Flow – Liquid Treatment (RO)

Average Daily Flow

198, 542 gpd

Maximum Daily Flow

398, 367 gpd

Flow – 1.3% Lost to RO

Average Daily Flow

2, 590 gpd

Maximum Daily Flow

4,970 gpd

Portable Water Existing Plant

Average Daily Flow

148, 163 gpd

Maximum Daily Flow

297, 317 gpd

Choice of Equipment

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 31

There are various equipment that were designed to meet the requirements of each step of

the water recycling method. The following table shows the proposed equipment for the project.

Equipment

Description

Capacity

Pump

For pumping the water

into the treatment chamber

410,000 gpd

GE Water (Packaged

Plant)

Membrane bioreactor

for primary treatment

410, 000 gpd

Huber tech (Rotomat

Rotary Screw thickener)

Solid waste handling

500, 000 gpd

GE Water (Model

1225595, RO PRO-150-PRE)

Reverse osmosis

300, 000 gpd

Wedeco ITT

Ultra Violet treatment

for disinfection.

420,000 gpd

Cole Parmer

Chlorination

23.80 gpd

Membrane Bioreactor

The choice of the membrane bioreactor is based on the average and maximum flow per

day. The chosen membrane bioreactor meets the required flow requirements for the Milton

Keynes water supply system. The Zenon model was chosen due to its impressive contaminant

removal properties. The removal rates for the contaminants are as in the table below.

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 32

Reverse Osmosis Membranes

The reverse osmosis membrane is installed to improve the quality of the effluent water

from the bioreactor membrane. The reverse osmosis acts as a polishing method to clean the water

to meet the standards for drinking water and TO make the water safe for consumption. The

reverse osmosis is used to treat the water to make it safe for consumption. The reverse osmosis

plant was obtained from the same manufacture packaged in the membrane bioreactor. The loss of

water during the reverse osmosis process was estimated at 1.3% due to the rejected contaminated

water.

Results and Discussion

According to findings of this research, there are various types of water recycling

technologies use in various municipalities, and each one of them has a different advantage and

disadvantage depending on the requirements of the system. For instance, the choice of a water

treatment technology mainly depends on the intended use of the water. For instance, if the water

is meant to be used for landscape irrigation or toilet flushing, then the primary treatment process

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 33

may be enough to treat the water. However, treating drinking water will require a series of

treatments including secondary and tertiary treatments to ensure that the final effluent water

meets the specified safety standards.

From the data obtained through the design, the Milton Keynes water supply system is

expected to have an additional 297, 317 gallons of clean and recycled water per day. The table

below shows the amount of water entering and leaving every section of the treatment plant as

well as the final amount of clean water leaving the facility.

Flow – Liquid Treatment (MBR)

Average Daily Flow

201, 132 gpd

Maximum Daily Flow

403, 337 gpd

Flow – Solid Treatment

Average Daily Flow

4, 132 gpd

Maximum Daily Flow

8, 337 gpd

Flow – Liquid Treatment (RO)

Average Daily Flow

198, 542 gpd

Maximum Daily Flow

398, 367 gpd

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 34

Flow – 1.3% Lost to RO

Average Daily Flow

2, 590 gpd

Maximum Daily Flow

4,970 gpd

Portable Water Existing Plant

Average Daily Flow

148, 163 gpd

Maximum Daily Flow

297, 317 gpd

The differences in the amounts of water entering and leaving each section of the

treatment plant can be associated with various factors which are specific to each treatment stage.

For instance, there are two sections of the recycling plant which require supplementary water

apart from the wastewater alone. The first section is the solid treatment which requires a supply

of water from a third party source. The reverse osmosis section also requires supplementary

water from a third party source. The 25% loss in the RO chamber is associated with the amount

of water rejected during the purification process.

Effluent Quality

From the design considerations and choice of equipment to meet the standards for clean

water, the quality of water coming out of the facility is represented in the following table.

Contaminant

Concentration

Turbidity

1NTU

TSS

5 mg/L

IMPACT AND DESIGN OF WATER RECYCLE SYSTEMS 35