A B O O KR E P O R T B Y :

Carlos Miguel

T H E W A T E R W I S E G U I D ET O

DIYConstructed

Wetlands

Build a mini wetland in your garden to treat your household greywater

Compact design for small gardens

Do-it-yourself design

Re-use your greywater

Attract wildlife into your garden

G R E Y W A T E RWater from your shower, bath, and laundry can be used to irrigate your garden.

Greywater is household wastewater that doesn’t contain any faecal matter, heavy

grease or toxic chemicals. Water from kitchen sinks, that does not contain a lot of

grease or animal derivatives like blood, may also be used. Typically greywater

contains nitrate, phosphate, soaps, salt, bacteria, bleach, foam, food particles,

organic matter, suspended solids, perfumes and dye.

Watering your garden with untreated greywater may affect the health of soil and

plants. It is important to be aware of what is in your greywater, and to flush areas

watered with greywater, with tap or rainwater to remove salts and other

chemicals.

Making use of a constructed wetland to filtrate and treat the water before it is

used in the landscape is beneficial to your garden health, as it reduces the amount

of toxins, bacteria, and other chemicals that may be present in greywater.

U S I N G G R E Y W A T E RIn South Africa, municipal water use, which includes domestic water and

water used in the garden, is indicated at being 27% of the total water used.

A major component of domestic water consumption is gardening, estimated

at 31-50% of the total water used. The use of water for irrigating the

gardening can be reduced drastically if homeowners implement the

following initiatives:

• Use of Water Wise gardening concepts, such as planting in hydrozones,

and using drought resistant indigenous plants;

• Mulching of soil to preserve soil moisture;

• Efficient irrigation systems and irrigation scheduling;

• Rainwater harvesting;

• The reuse of wastewater (greywater).

Greywater can be used safely in the garden if you follow a few basic rules.

Greywater that is stored for more than 24 hours can develop odours. A

constructed wetland will filter and treat your greywater before you use it to

irrigate your garden. The system removes soap scum, toxins, and bacteria

and delivers better quality water to your garden. It also provides a habitat

for local and indigenous insects, birds, and animals, and provides an

aesthetically appealing focal point in the garden.

Avoid watering fruits and vegetables directly with greywater if they will be eaten raw. Thereis a chance that pathogenic organisms may be present in wastewater even after treatment.

What is greywater?Greywater sources

Blackwater sources

A wetland is a system of shallow, water-logged soil and aquatic vegetation that acts as a bio filter with nutrient

uptake abilities and the capacity to remove heavy metals and toxic substances. The up-take of toxins and other

substances occurs through the plant roots. A constructed wetland is a man-made wetland that mimics the

natural processes of a wetland to treat water. Greywater is passed through the wetland, where it is slowly

cleaned and filtered, and then released. The root system of the plants releases oxygen into the water and this

creates a suitable environment for aerobic microbial and fungal activity (biological breakdown of pollutants

and organic materials).

Artificial or constructed wetlands can be constructed with any material that will hold water:

Brick walls that are waterproofed

Concrete

Plastic liner

Pre-manufactured plastic containers like plastic drinking troughs

Fibreglass

Rubber liner

What is a ConstructedWetland?

D O Y O U L I V E I N A D O L O M I T I C A R E A ?Additional care and deliberation must be taken if the site is situated on underlying dolomitic geology. Dolomite might cause sinkholes. Rainwater and percolating ground water gradually dissolves the rock overtime as it seeps through joints, fractures and fault zones in the rock. The dissolution of the dolomite givesrise to cave systems and voids in the rock. Soils covering the rock can collapse into these caves or voidsresulting in catastrophic ground movement on the surface such as sinkholes or dolines. However, there arealternatives for homeowners living in dolomitic areas. Homeowners have to make sure they adhere to theseguidelines:

Plastic water troughs are ideal to ensure that water does not leakfrom the system.Rigid material facilitates easy connection of pipes and waterproofconnections.Space saving: they can be used in very narrow spaces such ascorridors along the house.They can be stacked using multiple troughs in line for higherwater capacities.Easily maintained.Low-cost installation.Quick and easy installation.

The constructed wetland should be raised above ground.The basin must be a waterproof container such as a cattle watering trough.You must be able to check for any leakages.

BENEFITS TO USING IMPERMEABLE CONTAINERS

Dolomite land occupies up to 25 % of Gautengand underlies some of the most denselypopulated areas such as Vosloorus, Thokoza,Centurion, Dobsonville, Katlehong andWestonaria.

Refer to http://www.gov.za/documents/appropriate-development-infrastructure-dolomite-guidelines-consultants for more details and guidelines on dolomitic areas.

Size (surface area) required = X (number of people per household) x 1.5 m

Your step-by-step guide tobuilding a Constructed Wetland

D E T E R M I N E T H E S I Z E S U I T A B L E F O R T H E V O L U M E O F G R E Y W A T E R1

(4) x 1.5 = 6 mThe size formula used allows for the water to be retained in the system for about 4 days toensure sufficient contact time with the medium and microbes for proper cleaning of water.

2 D E M A R C A T E T H E S I T E A N D S H A P E O F T H E W E T L A N D

The shape of the wetland does not have to be exact. The long shape of a rectangle has the benefitof increasing the distance between the inlet and outlet and ensures directional flow of water fromthe inlet (dirty water) to the outlet (clean water) without it mixing. For example, a 6m wetland can be 1m x 6m OR 2m x 3m OR 1.5m x 4m

3 E X C A V A T E T O T H E R E Q U I R E D D E P T H O F T H E W E T L A N D

The excavation for the wetland is called a basin. The basin can be between 300mm and 600mmdeep, but should be at least 400mm deep to allow greywater to fill up to, and remain at a level thatis 5cm below the upper surface of the gravel. This promotes water flow through the root-zone of theplants and ensures proper contact with the medium and microbes. Make sure that the top level ofthe basin is lower than the height of the inlet of the source (washbasin / shower floor etc.) for gravityflow to apply. The bottom of the basin surface and the level of the gravel media should be flat.

https://www.researchgate.net/profile/Sarah_White14/publication/258697505/figure/fig2/AS:297332278087694@1447900947960/Water-flow-path-through-a-subsurface-flow-constructed-wetland.png

EXAMPLE:

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L I N E T H E E X C A V A T E D B A S I N W I T H P L A S T I C L I N E R4A flexible, but puncture resistant and durable impermeable plastic liner, or similar suitable material,will be required. Clay or clay type materials (e.g. bentonite) is not suitable as a liner and shouldnever be used for this type of wetland, as clay is porous and will alllow untreated greywater to filterinto the ground. Polypropylene or Linear Low Density Polyethylene (LLDPE) of 0.75 – 1mmthickness is the recommended material. It should be installed without any joints and should be onesingle sheet (usually 3m wide). The use of waterproof containers is a good alternative and resultsin less labour.

5 A D D T H E G R A V E L M E D I U M T O T H E B A S I N

Good quality gravel that will not crumble or degrade into fine particles is recommended. Crushedangular stone is preferred because it will leave spaces in between and allow more surface area forthe development of microbial growth. The optimal size of the crushed rock / gravel is between 13 –19mm. Water level should be maintained just below (5cm) the gravel surface by adjustment of theoutlet pipe level. The gravel surface can be accurately levelled using a rake, by filling in the basinwith water and using the water surface as a guide.

I N L E T A N D O U T L E T P I P E S6To prevent any issues with odour from the grey water, the inlet should be just above the gravelbed. No ponding or pooling of water should occur anywhere on the surface of the gravel. For the outlet, a hole is cut in the plastic liner at a level just below the final water level (imagebottom right). Attach a tank connector and piping here to receive the clean water. The treated wateris then removed from the wetland and directed either into the garden or into a water storage tank.

7 F I L T E R / G R E A S E T R A P

The filter can be assembled using common items bought at your local hardware store. You willneed a drain grid, a pool weir basket, a round plastic plant pot (20 cm) and a square rainwater pit.Place the plant pot in the rainwater pit, and the weir basket into the plant pot. Then, place the draingrid over the rainwater pit. You can drill holes into the lip of the rainwater pit to securely fasten thedrain grid.

O P T I O N A L P U M P8The treated water can be stored temporarily in a 'storage tank' before it is pumped to the desiredlocation for use in the garden. The sump can be easily installed using a normal 100L plastic crate.Larger tanks can also be used. The crate is installed at a level just above the water and top ofgravel level at the furthest end within the wetland. The inlet pipe is installed just below the waterlevel to fill the storage crate when full. Inside the crate goes the the pump, which is a submersiblepump, that switches on when water reaches a certain level and switches off below a certain level.When the pump is switched on it will pump the water outside the storage crate.

https://www.waterpathogens.org/sites/default/files/Constructed%20Wetlands%20-%20Figure%201.jpg

W E T L A N D P L A N T S9Initially, the wetland must be filled up with clean water to just below the surface of the gravelmedium to ensure that the newly planted plant roots are in contact with the water to enableestablishment and growth. Once establishment has taken place, the water level can be lowered tothe recommended 5cm below surface. Young plants should be planted from 1 – 1.5L containers at4-6 plants per square meter. Care should be taken to remove most of the soil from the plant roots before planting to avoid theclogging of the pores between the gravel stones with sediment. The areas around the inlet andoutlet should be left unplanted, leaving the coarse-gravel clear for the movement of water. Choose a diversity of plants suitable to the area that not only complement one another, but alsoprovide an aesthetic appeal throughout the different seasons of the year.

SOME RECOMMENDED PLANTSA large number of species can be used, but the following arerecommended species for the Gauteng area:

Berula erecta Lesser water-parsnipCrinum bulbispermum Orange river lilyCyperus alternifolius Umbrella sedgeCyperus denudatusCyperus prolifer Miniature papyrusEliocharis dregeana Finger sedgeFimbristylis complanata Juncus oxycarpaKniphofia ensifolia Torch lily Schoenoplectus brachycerasTypha capensis BulrushZantedeschsia aethiopica Arum lily Crinum bulbispermum Eliocharis dregeana Kniphofia ensifolia Berula erecta Zantedeschia aethiopica

Operational managementW E T L A N D M A I N T E N A N C E

During the first growing season, it is important to remove weeds that can compete with the plantedwetland vegetation. With time, the gravel will become clogged with accumulated solids andbacterial film. The roots of the plants will spread and impair water flow after a period of time, whichmay cause the wetland to dysfunction or overflow. If this happens and the system stops functioningefficiently, you will need to remove and wash the gravel. It is recommended that the gravel mediumbe washed approximately every 5 years. To do this, leave a thin layer of gravel to protect theplastic liner from damage. Remove the rest of the gravel and wash it with rain or tap water.Replace the gravel. Some plants are deciduous and the leaves will die down in harsh winter climate, but will regrow inthe warmer season. This will reduce the functionality of the wetland slightly and should be takeninto consideration. MAINTENANCE ACTIVITIES

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Frequently check and clean out the grease / fat trap or filter system. Discard this waste into yourdomestic waste bin.Frequently check that the water stays at a level 5cm below the surface of the gravel medium toprevent odours and to prevent vegetation roots from drying out.Monitor plant health and replant any dead vegetation or bare areas.Check for adequate inflow and outflow and identify any blockages or damage to pipework orliner.Avoid shading of wetland vegetation by overhanging trees or accumulation of leaves fromaround the site. Keep an open-air space above and around the wetland.Cut back frosted plants at the end of winter to encourage new growth in summer.Prevent harmful chemicals like bleach from entering the wetland in high concentrations that willadversely affect the natural biota of the wetland.

Wetland design elements

Figure 1. E. coli levels in greywater before and after treatment with a constructed wetland.

Use these technical drawings asan example to better understand

the design of the constructedwetland when you implement it

on your property.

Research into wetland effectivenessA research project was conducted to analyse the effectiveness of constructed wetlands in treatinggreywater and removing contaminants so that the water would be suitable for use in the garden. This wasdone to ensure that the water treated by the wetlands would be clean enough for you to use safely andsustainably. The graph below shows a significant reduction in the amount of E. coli bacteria in greywaterafter treatment with a constructed wetland.

In conclusion, scientific data shows us that these constructed wetlandsare effective in removing certain contaminants from greywater,making the treated greywater safe for use in your garden*.

*Remember, it is always important to be careful when handling greywater to preventcontamination with potentially harmful bacteria. Please follow these hints and tips whendealing with greywater:

Do not:Let children and pets drink or play in or around greywater.Allow greywater to flow into water courses, swimming pools or dams.Hose, spray or mist with greywater, as this may introduce pathogens into the air, which could be inhaled.

Do not use greywater if:It has come into contact with a toilet or urinal, unless effectively and suitably treated.It has been used to wash nappies or other clothing soiled by faeces and/or urine.

Do not allow greywater to:Leave the boundaries of the property on which it is generated.Pond or pool where mosquitoes and other insect vectors of disease can breed.Remain stagnant and unused for more than 24 hours, unless suitably treated.Do not use greywater to irrigate vegetables that will be eaten raw or uncooked, unless it has been suitablytreated.

Figure 1. E. coli levels in greywater before and after treatment with a constructed wetland.

Construction materials and costYou need a budget of between R 3 500 and R 7 100 depending on the requirements of piping andpumps. If you situate the wetland in close proximity to the source, fewer pipes are required. If thetreated water is used locally or on a sloped site, it does not need a pump. All the material for the construction of a wetland can be found at your localhardware store (prices as of 2019). Wetland components R 2 200 (basic requirements)Planting R 500 - R 900Fat / grease trap R 500 Pump and Tank R 3 500 (optional extra)

Wetland components: R 2 200

50 mm PVC pipe @ R 30 / mx 15 mR 450

50 mm PVC straight @ R 12 eax 3R 36

50 mm PVC elbow @ R 7 eax 3R 21

50 mm PVC 45 deg @ R 12 eax 2R 24

50 mm PVC tee@ R 15 eax 2R 30

13 - 19 mm concrete stone@ R 410 / mx 2.4 m R 984

50 mm end cap@ R 10 eax 2R 20

50 mm tank connector @ R 90 eax 1R 90

250 micron plasticmembrane 3 m wide @ R 500 / 30 mx 7 mR 500

Basic wetland components

Construction materials and cost

Grease / fat trap = R 427

Rain water pit @ R 160 eax 1R 160

Grid@ R 74 eax 1R 74

25 mm elbow @ R 14 eax 2R 28

25 mm socket @ R 24 eax 2R 48

25 mm pipe@ R 10 / mx 2mR 20

20 cm pot@ R 37 eax 1R 37

Weir basket @ R 60 eax 1R 60

Fat / grease trap components

100 litre crate@ R 210 eax 1R 210

Sump and pump = R 3 210

Water pump@ R 3 000 eax 1R 3 000

Sump and pump components

C O N T A C T U SFor more information on Water Wise and grey water solutions,

please visit the Rand Water website at www.randwater.co.za and

click on the Water Wise logo. Alternatively, call us at 0860 10 10 60

or email us on waterwise@randwater.co.za.

This booklet was developed by:Rand Water - Water WiseGIBB Engineering and Architecture

Water Plants: Abrus Enterprise Ivan van der Walt Aqua Flora Pieter van der Walt Water Trough: Abrus Enterprise Ivan van der Walt Materials: Most hardware stores. Grease Trap: Abrus Enterprise Ivan van der Walt Wetland Water Quality and Research: Rand Water Samanta Stelli

A C K N O W L E D G E M E N T S