Lecturer:Mariska Ronteltap

m.ronteltap@unesco-ihe.org

Treatment aspects for urine, faeces and greywater

Course 2 Unit 1Part A B C D

Teacher

Mariska Ronteltapm.ronteltap@unesco-ihe.org

Course 2 Unit 1

Part D: General treatment aspects for greywater

Notes:

• For characteristics of greywater, see Course 1 Unit 2• The US-American spelling is graywater• Some people think that ecosan is only about toilets, urine and faeces; but in fact, a holistic ecosan project should also include a strategy for greywater.

Simple scenario of greywater reuse in the garden

Course 2 Unit 1

Reminder: main treatment aim for greywater

Sanitisation (= pathogen kill) protect public health !

Groundwater protection

Enable safe reuse

Secondary treatment aims specific for greywater

Organic matter removal

Odour removal

Nutrient removal (if discharged to water course)

Some general remarks on greywater management

This is a growing topic even outside the ecosan community, i.e. as part of the “conventional” sanitation approach

Is practised more and more widely also in industrialised countries, particularly in Australia

Many equipment suppliers now on the market

The challenge is though to find low-cost solutions applicable for developing countries

I recommend the recent publication by Eawag (Morel and Diener, 2006)

www.watercasa.org

“Greywater: don’t lose it – use it”

Definition of greywater (reminder)

Greywater is defined as household wastewater with minimal input of human excreta

It includes used water from baths, showers, hand basins, washing machines, dishwashers, laundries and kitchen sinks

Greywater is all domestic wastewater except toilet waste

My daughter Hanna in 2006, learning about greywater at an early age...

Open greywater drains in slum in Dhaka, Bangladesh(photos provided by Marius de Langen, UNESCO-IHE)

Do you have your own photos of indiscriminate greywater discharge in your town?

Course 2 Unit 1

General objectives for greywater management

1. To protect public health (prevent spreading of water-borne diseases)

2. To prevent deterioration of (non-sealed) roads and foot paths

3. To avoid damage to buildings and surrounding areas from inundation, waterlogging and freezing

4. To avoid creation of bad odours, stagnant water and breeding sites for mosquitoes

5. To prevent eutrophication of sensitive surface waters6. To prevent contamination of groundwater and

drinking water reservoirs7. To use greywater as a resource for urban

agriculture, irrigation, aquifer recharge and landscaping

Source: Ridderstolpe (2004) – formulated mainly with industrialised countries in mind

Drivers for separate greywater treatment

Greywater is easier to treat than conventional (mixed) wastewater, because it contains almost no pathogens and little ammonia nitrogen

Drivers for treated greywater reuse

• Reduces potable water demand– There is a need for water for urban agriculture (see also

Course 3 Unit 2 “Urban agriculture and ecosan”)• Augmentation of river flows• Aquifer recharge Improved sustainability of water resource management

Treated greywater reuse options (Urban) agriculture and aquaculture Irrigation: landscape, golf courses Municipal uses

- E.g. Fire protection, street cleaning, car washing, cooling, boiler feed and road construction operation

Non-potable domestic uses - Toilet flushing, air conditioning, laundry, floor

cleaning Use for recreation

- Ponds, lakes, streams and fountains Discharge to surface water, percolation to

groundwater

replacing potable water

replacing potable water or untreated mixed wastewater (e.g. Accra (Ghana), Lima (Peru))

Rule of thumb for treated greywater reuse options

You can use it for anything that does not require water of potable quality

- So anything except drinking, cooking and perhaps teeth brushing (and showering/bathing)

This rule of thumb applies to the normal low-cost treatment methods. If you went for high-tech methods such as membrane, UV, ozonation etc. then eventually you would get drinking water quality.

Greywater reuse system elements

• Generation/separation, collection and transfer– Can use thinner pipes because no faeces– Equip pipe systems with ventilation and water traps to

prevent odour– Low-cost options for communities:

• Small-bore sewer systems (see Course 2 Unit 8)• Open drains (less desirable but cheaper)

• Treatment– Pre-treatment– Main treatment– Post-treatment

• Storage, reuse/recycle and disposal

Course 2 Unit 1

see following slides for further information

Example 1: Components of a greywater management system at household level

For low-income areas, the more appropriate solution is likely to be at neighbourhood or even community level (i.e. semi-centralised)

Source: Ridderstolpe (2004)

greywater treatment for individual house

Example 2: Richard Holden’s house in

Johannesburg, South Africa (slide 1 of 2)

He uses only pre-treatment with a screen but no main treatment step

Small greywater storage tank to prevent odour (just a pump sump)

Example 2: Richard Holden’s house in Johannesburg, South Africa (slide 2 of 2)

Drip and spray irrigation in the front and back garden

Only possible with sufficiently large garden and a climate that is not too wet, and suitable, well-draining soil

See also separate presentation on entire system (“UDD system at Holden’s house.ppt”) in Course 1 Unit 3 extra material

Purposes of greywater treatment stepsTreatment step Purpose of treatment step Examples for process options

Pre-treatment

(= primary treatment)

Remove suspended solids, particles, fibres, hair, grease

Coarse filtration (drain screens, simple coarse filters, gravel and sand filters), flotation (grease traps), septic tanksa, UASBa, settling tanks

Main treatment

(= secondary treatment)

Remove organic matter (BOD) – also reduce potential for odour

Constructed wetlandsb, pondsa, trickling filters, anaerobic filters, unplanted vertical-flow filters, septic tanksa

Post-treatment (= tertiary treatment)

Further polishing and disinfection; reduce organic pollutants and heavy metals

Disinfection (UV, chlorine)

Sand filters, constructed wetlandsb, aerobic attached biofilm processes

Note: Greywater has high levels of easily degradable organic compounds potential strong source of smell if not managed properly

a See Course 2 Unit 4 (“Introduction to anaerobic treatment”) (UASB = Upflow Anaerobic Sludge Blanket reactor)b See Course 2 Unit 5 (“Introduction to constructed wetlands”)

The degree of greywater treatment required is dependent on:

Public health risk that can be tolerated (tolerable risk and health-based targets, see WHO (2006))

-This will also be discussed further in Course 3 Unit 1 “Reuse of ecosan products in agriculture”

-Prevalence of water-borne diseases in population Population density Type of reuse application Receiving environment:

- Soil type, structure, groundwater level (if infiltrated into soil)

- Size and sensitivity of aquatic environment (if discharged to water body)

Course 2 Unit 1

Some photos of treatment processes (these will all be described in more detail later)

Septic tank (Australia)

Ponds (lagoons) Constructed wetlands

Treatment scheme with septic tank and sand filter

Notes on terminology for greywater main

treatment processes (all these different names for the same thing can be quite confusing!)

Vertical-flow filters are also referred to as subsurface biofilters, percolation beds, infiltration beds or intermittent sand filters

- Multi-layer percolation bed may have (from top to bottom): mulch*, topsoil, sand, gravel, stones.

Horizontal-flow planted filters are also called constructed wetlands

Vertical-flow planted filters are also called constructed wetlands

* Mulch: In agriculture and gardening, mulch is a protective cover placed over the soil, primarily to modify the effects of the local climate. A wide variety of natural and synthetic materials are used. (source: www.wikipedia.org)

Source: Morel and Diener (2006)

Course 2 Unit 1

Example 3: Rural communities in Jordan (1/4)

• Integrated Wastewater Management of Marginal Communities in Jordan

• 35 small & scattered rural communities in the arid area of Jordan

• Pit latrines used for excreta disposal, so household wastewater is in fact greywater

Source: Source: Sahar DalahmehSahar Dalahmeh ( (Royal Scientific Society Royal Scientific Society Environment Research CenterEnvironment Research Center), 28 July 06, Short Course ), 28 July 06, Short Course participant at IHEparticipant at IHE

Working with the communities in identifying best techniques, technologies and practices for greywater treatment and reuse (2/4)

pH: 6.69BOD: 930 mg/LCOD: 2367 mg/LTSS: 829 mg/L

TKN: 99 mg/LFOG: 171 mg/L (fats, oil and grease)E. coli: 5.0x105 MPN/100 ml

Generation rate: 20 L/cap/d

Concentrated greywater

This is very low. People use water several times: first shower/bath, then laundry, then floor cleaning. Typical value in Germany would be say 100 L/cap/d.

Septic tank & intermittent sand filter (ISF)

Treatment technology selection criteria: source characteristics (quality & quantity), community requirement (cost, operation and maintenance), local standards for reuse, and recieving environment)

Upflow anaerobic sludge blanket reactor (UASB)

Outputs (slide 3 of 4)

Course 2 Unit 1

2 options short-listed

Septic tank & intermittent sand filter for one household (4/4)

Technologies for main treatment step of greywater

• Biological low-rate systems (“natural” systems): – Constructed wetlands, vertical soil filters, soil

infiltration - most common– Ponds – Septic tank or UASB plus sand filters

• Biological high-rate systems (with biofilms): – Trickling filters– Rotating biological contactors (RBC)

• Membrane treatment: – Membrane bioreactor (MBR) (also a biological

high-rate system)– Nano-filtration, ultra-filtrationNotes:

Activated sludge process not normally used (not compact enough; no need for biological nutrient removal)

low-tech, see Course 2 Unit 4 & 5 for more details

high-tech, see later in this presentation for more details

Example: experimental mulch bed for greywater treatment (after settling)

This mulch bed of 6 m2 area treats shower water from communal shower block at the allotment garden Listudden in Stockholm, Sweden

Left: Open box to show sampling wells for influent and effluent

How to select the most appropriate process?

• Use again sustainability criteria (see Course 1 Unit 1 and also next slide)

• Based on strength of greywater (amount of organic matter)– My rule of thumb: Use anaerobic processes* for high-

strength greywater (BOD > 400 mg/L), use aerobic processes for low-strength greywater (BOD < 400 mg/L)

• Based on required quality for reuse or discharge

* Anaerobic processes: e.g. Septic tanks, UASBs, ponds (they need polishing with aerobic treatment or other processes before discharge (e.g. constructed wetlands)) – See Course 2 Unit 4 on “Introduction to anaerobic treatment technologies”

Comparison of options for main treatment step of greywater

Technology Biological low-rate Biological high-rate

Membrane

Capital investment Low Medium High

O & M cost Low Medium High

Effluent quality Medium Medium High

Operator skills required Low Medium Medium

Robustness High High High

Land requirement High Medium Low

“high-tech”

“low-tech”

Course 2 Unit 1

Keep in mind biological sludge production in each case (needs treatment, e.g. dewatering, drying, reuse)

Example: decision tree for determining appropriate greywater disposal/treatment

options (for South African unsewered areas)

This is a proposed simplified decision tree from Carden et al. (2007)It is specific for the South African context, but just to give you an example

Greywater treatment: use existing know-how and know which route to take

Same processes as used for conventional (mixed) wastewater but greywater contains:• fewer pathogens• lower ammonia-N and phosphorus• no industrial effluent

Processes also used for drinking water treatment (sand filters, membranes, ozone, UV, etc.)

Other additional risk management measures (as described in WHO, 2006)

Direct or indirect planned non-potable or even potable reuse

Irrigation in (urban) agriculture

+

Route A

Route B

Which route would be most suitable in your city?

Greywater treatment, main treatment step

Post-treatment step

Multiple-barrier approach

Some further descriptions of more “high tech” greywater treatment methods (for main treatment step)

The following processes will be described in the following slides:

1. Trickling filters

2. Rotating biological contactors

3. Membrane bioreactors

1 - Trickling filters for greywater treatment (main treatment step)

= a non-flooded packed bed of media (rock or plastic), where the void volume is air, and which is covered with biomass, and over which wastewater flows downwards.

Trickling filter in England used for conventional mixed wastewater treatment (could also be used for greywater treatment, at a smaller scale)

Characteristics of trickling filters

• Treatment process is aerobic (requires presence of oxygen)

• Biomass (biofilm) attach to rock or plastic media• Wastewater (after primary settling) distributed

continuously over the media• Simple, energy-efficient operation• Very low operating costs• Can achieve high BOD removal, good nitrification,

and some nitrogen removal

Course 2 Unit 1

Trickling filter media types

• Rock (most common, see next slide)

• Plastic, structured media– Vertical flow

– Cross flow

• Plastic random pack

www.munters.com/www/uk/home.nsf

Trickling filters with rock media

2 - Rotating Biological Contactor (RBC) for greywater treatment (main treatment step)• Fixed film aerobic systems • Biomass (biofilm) attached to a partly or fully

submerged rotating media in wastewater• Media rotation by mechanical drive or air• Limited nitrification• Used in package-plant design

Course 2 Unit 1

Rotating biological contactor (RBC) plants (“package plants”)

These photos are for conventional mixed wastewater treatment but the plants would look the same if they were treating greywater

Source: http://www.klargester.de/1_50.htm

3 - Membrane bioreactor (combined main and post-

treatment step for greywater)• The membrane bioreactor

(MBR) couples the activated sludge process with membrane filtration for sludge separation

• Construction and O&M costs are relatively high (high energy demand for aeration)

• Regarded as a “high-tech” solution

• Produces excellent effluent quality, with extremely low pathogen concentrations

• Useful also for industrial wastewater (e.g. www.triqua.nl)

Source of photos: http://www.water-technology.net/projects/carnation/carnation6.html

Post-treatment options for greywater

• Polishing (= further solids removal):– Sand filters– Granular activated carbon (GAC)– Wetlands– Sorption and irrigation systems

• Disinfection:– Chlorine (simple O&M, inexpensive, but strong smell, disinfection

by-products)– Ultra Violet (UV) (no change of smell/color of water)– Ozone (powerful disinfectant, expensive)– Membrane filtration (e.g. as part of MBR process)

Course 2 Unit 1

Schematic of greywater reuse system for medium scale community

Greywater

Sedimentation

e.g. Wetland, Pond, RBC, TF,

MBR, UF, NF

Disinfection

Storage

Reuse activities

collection

pre-treatment

main treatment

post-treatment

recycle

Potential environmental and public health risks with greywater reuse in agriculture

Potential risk Reason

Spreading of disease Pathogens from greywater may spread by direct contact (i.e. touching greywater or inhaling infectious water droplets) or indirectly by consumption of contaminated food

Contamination of food Harmful chemicals and pathogens can be absorbed by vegetables

Damage of soil structure Solid particles, chemicals in greywater will cause land application systems to block and alter soil acidity/alkalinity balance

The public health risks are much lower than when using treated (or untreated!) conventional domestic wastewater (wastewater which includes human excreta)

Public acceptance of greywater reuse (for industrialised countries)

• Public acceptance for certain reuse options is usually high:– Toilet flushing– Garden watering (e.g. in Australia)

need dual plumbing

• Lower acceptance for reuse options such as:– Laundry– Bath / shower

In developing countries, level of public acceptance is generally relatively high, and it is certainly much safer than the current common practise of using raw (untreated) mixed domestic wastewater for urban agriculture.

Guidelines for greywater reuse

• Reuse in agriculture– Since September 2006 we have the new WHO

guidelines (see next slide)

• National reuse guidelines in countries with existing reuse practises, e.g:– China– Australia, Denmark, Norway, Sweden, Germany, Japan,

USA

Course 2 Unit 1

WHO Guidelines

• Third edition of the Guidelines for the “Safe use of wastewater, excreta and greywater” is presented in four separate volumes:– Volume 1, Policy and regulatory aspects – Volume 2, Wastewater use in agriculture – Volume 3, Wastewater and excreta use in aquaculture – Volume 4, Excreta and greywater use in agriculture

• http://www.who.int/water_sanitation_health/wastewater/gsuww/en• Volume 4 of the Guidelines provides information on the assessment

and management of risks associated with microbial hazards. It explains requirements to promote the safe use of excreta and greywater in agriculture, including minimum procedures and specific health-based targets, and how those requirements are intended to be used. This volume also describes the approaches used in deriving the guidelines, including health-based targets, and includes a substantive revision of approaches to ensuring microbial safety.

A key sentence from the introduction of the WHO guidelines

“Traditional waterborne sewerage will continue to dominate sanitation for the foreseeable future. Since only a fraction of existing wastewater treatment plants in the world are optimally reducing levels of pathogenic microorganisms and since a majority of people living in both rural and urban areas will not be connected to centralised wastewater treatment systems, alternative sanitation approaches need to be developed in parallel.” (WHO, 2006, p. xiii)

• More information about these guidelines will be given in Course 3 Unit 1 “Reuse of ecosan products in agriculture”)

Remarks about the situation in Australia

Main proposed technical solutions:– Seawater

desalination with reverse osmosis

• This is energy intensive: increased costs of water and more CO2 emissions!

– Reuse of treated wastewater (the public is worried about health risk and does not like this option but sometimes are not given a choice)

An ecosan-type approach would be:– Separate out the greywater

and treat and reuse it (advantages: much lower pathogens, no industrial component, decentralised reuse)

– Get serious about water demand management

• 250 L/cap/d for wastewater production (in 2000)

• Compare with current value in the Netherlands: ~ 120 L/cap/d

– Change agricultural practices away from plants with high water demand (e.g. cotton)

There are now problems with emerging water shortages due to climate change and population growth, e.g. in South-East Queensland

Do you have a similar situation in your country?

Golf course irrigation – often still with potable water!

Name of the company Country of origin Name of the products

Australian waterlines Australia GreyWatersaver

Eco Design Sustainable Housing Australia Grey Water Diverter

Nature Loo Australia Nature clear

Environ-friendly Australia Wattworks Grey Water System

Environ-friendly Australia Eco Care

FBR Germany FBR Grey Water recycling system

Some example companies specialising in greywater treatment (there are many more!)32

Some other useful suppliers’ websites:– www.oasisdesign.net/greywater/index.htm– www.greywater.com

Example list of advice regarding greywater: Greywater Do’s : we should…• Only use wastewater from baths, showers, hand basins and washing

machines (preferably the final rinse water) • Only use greywater on the garden and rotate which areas you water. • Only apply enough water that the soil can absorb• Wash your hands following watering with greywater • Stop using greywater during wet periods • Stop using greywater if odours are generated and plants do not

appear to be healthy • Grey water that can be reused straight away without the need for

pre-treatment includes greywater from the shower, bath and laundry rinse cycle.

• Choose phosphate-free or low-phosphate household cleaners and detergents.

• Install a lint filter in your washing machine.

Source: an Australian website (I can’t find it anymore)

Greywater Don'ts: We should not…• Water vegetable gardens if the crop is to be eaten raw or uncooked • Use greywater that has faecal contamination, for example wastewater used to wash

nappies • Use kitchen wastewater (including dishwashers) due to the high concentration of

food wastes and chemicals that are not readily broken down by soil organisms • Store greywater for more than 24 hours • Let children or pets drink or play with greywater • Allow greywater to flow from your property or enter stormwater systems • Use greywater if any member of your family is suffering from gastroenteritis. • Irrigate your garden with greywater in wet weather, or if the soil is already sodden. • Allow greywater to form pools or ponds in your garden. The microbes will thrive,

creating an offensive stink and a health hazard. • Allow your pets to drink greywater. • Let children play in garden areas irrigated with greywater. • Let greywater run-off reach your swimming pool and any other water features, like

ponds and birdbaths• Let the family eat without washing their hands before.• Urinate in the shower or bath.• Use water that has come in contact with the toilet, or any other toileting fixture such

as a bidet or urinal. • Reuse the water when you wash domestic pets, because of the high level of bacterial

contamination

Example for commercially available greywater reuse product (1/2)

Supplier statements:• Fresh water is first used for hand

washing and then flows into cistern to ultimately flush the toilet

• Result is 10% greater savings in total bathroom water usage than market leading Smartflush® technology

• This Caroma technology has been successfully independently tested and refined over a ten year period

• Extensive field trials have been conducted to ensure the presence of soapy water in the cistern has no adverse effect on internal cistern operating componentry Source: http://www.caroma.com.au/products/index_profile.html

Course 2 Unit 1

“Hello everybody,

I just want to comment on Peter’s experience about being surprised that the idea is considered to be "new" and the product is sold as a "new"idea. I agree with him. My experience from Japan is the same, this type of toilets are in use since many decades there. Even as a tourist, you can see and use them in almost every 'ryokan‘ (traditional B&B, traditional hotels, boarding-houses) and privatelyin many households.

Best regards,Zsofia Ganrot”

Source: EcosanRes Discussion Forum on 16 June 2007

Example for commercially available greywater reuse product (2/2)

References used in this presentation

• Carden, K., Armitage, N., Sichone, O., and Winter, K. (2007) The use and disposal of greywater in the non-sewered areas of South Africa: Part 2 - Greywater management options. Water SA, 33(4), 433 - 442. *

• Morel, A. and Diener, S. (2006) Greywater management in low and middle-income countries, review of different treatment systems for households or neighbourhoods. Swiss Federal Institute of Aquatic Science and Technology (Eawag). Dübendorf, Switzerland. http://www.eawag.ch/organisation/abteilungen/sandec/schwerpunkte/ewm/projects/project_greywater *

• Ridderstolpe, P. (2004) Introduction to greywater management, Stockholm Environment Institute, Sweden, www.ecosanres.org *

• WHO (2006) Guidelines for the safe use of wastewater, excreta and greywater: Volume 4, Excreta and greywater use in agriculture. World Health Organisation, Geneva, available: http://www.who.int/water_sanitation_health/wastewater/gsuww/en/ *

* Also provided on the I-LE under Assigned Reading or Extra Materials for this course unit

Course 2 Unit 1