waste water, home architect, home architects

Waste Water

TYPES OF WASTEWATER

There are two types of wastewater created in a home, each of which can be treated and used in various ways.

Blackwater is water that has been mixed with waste from the toilet. Blackwater requires biological or chemical treatment and disinfection before re-use. Black water should only be re-used outdoors.
Greywater is wastewater from non-toilet plumbing fixtures such as showers, basins and taps. Depending on its use, greywater can require less treatment than blackwater and generally contains fewer pathogens. Treated greywater can be re-used indoors for toilet flushing and clothes washing, both of which are significant consumers of water. Greywater can also be used for garden watering.

CALCULATING WASTEWATER VOLUME

The table below indicates the amount of wastewater you can expect from your home after applying simple water use efficiency measures.

BLACKWATER LITRES/PERSON/DAY
Toilet 22
GREYWATER LITRES/PERSON/DAY
Shower 56
Hand Basin 6
Kitchen tap 12
Dishwasher 5
Laundry tap 7
Washing Machine 27
Total - Greywater 113
Total - Overall 135

RE-USE WATER SUPPLY

The quality of your re-use water depends on your treatment system, the water's 'first use' and which chemicals are used in the home.

To reduce your treatment requirements:

Minimise use of cleaning chemicals such as coloured toilet dyes. Use natural cleaning products where possible;
Do not dispose of household chemicals down the sink or toilet. Contact your local council or water authority for information on collection services; and
Use a sink strainer in the kitchen to help prevent food scraps and other solid material from entering your wastewater.
Use a lint filter on the outlet from your washing machine. Replace as necessary.

WASTEWATER RE-USE IN URBAN AREAS

It is sensible to consider wastewater re-use if you live in an urban, sewered area and any of the following apply to you:

Efficiency measures for indoor and outdoor water use have already been undertaken. [See: Reducing Water Demand; Outdoor Water Use]
Water supplies in your area are often limited, eg during droughts.
You have a large garden which you water regularly.

WASTEWATER RE-USE IN RURAL AREAS

Households in rural areas typically have greater scope for reusing wastewater for the following reasons:

There is no centralized treatment service, therefore investment in a wastewater treatment system is a necessity.
Installing a re-use system in a new house, or adapting an existing treatment system to allow re-use, may not incur significant additional expenditure.
Water supply may be restricted, thus placing a premium on using water resources in the most efficient manner.
The regulations for reusing wastewater in rural areas are not as stringent as urban areas - there is more scope
for innovation.
The septic tank and absorption trench system is currently the most prevalent on-site wastewater treatment system in rural Australia. This system does not actively treat wastewater to remove pathogens, and therefore the treated wastewater needs to be disposed underground, rather than re-used.

REUSING WASTEWATER INDOORS

Greywater can be re-used indoors for toilet flushing and clothes washing. Toilets and clothes washers are two of the biggest users of water in an average household.

Reusing wastewater for toilet flushing will save approximately 65 litres of potable water in an average household every day.
Reusing wastewater in your clothes washer will save approximately 90 litres of potable water in an average household every day.

In order to re-use greywater indoors for toilet flushing and clothes washing you will need to firstly:

Separate greywater and blackwater waste streams.
Install a greywater treatment and disinfection system that provides a suitable level of treatment and meets local regulations.

Greywater can be directly diverted from the shower or bathroom sink drains for re-use in the toilet only. However, it should not be stored for more than a couple of hours before re-use or disposal to sewer.

PRECAUTIONS

Greywater must be treated and disinfected before storage and general re-use because:

* It can contain significant numbers of pathogens which spread disease.

* It cannot be stored for longer than a few hours untreated as it begins to turn septic and smell.
When reusing greywater for clothes washing discoloration of clothing from dissolved organic material may be an issue. This can be avoided by installing an activated carbon filter.

Re-use of blackwater inside the home is not advisable, even after treatment and disinfection.

TREATMENT SYSTEMS FOR INDOOR RE-USE

Domestic greywater systems require an accreditation certificate to be sold commercially in most states. Check with your local council or state health department. Owner built systems generally require only Council approval.
There are many different types of greywater treatment systems, a few examples are given below. Refer to the reference list at the end of this sheet for further information and contact your local council for a list of suppliers in your area.
Greywater needs to be filtered before being treated in order to remove large waste particles. A coarse filter for greywater can be quite simple. See the diagram above for an example for owner operators. It comprises a waterproof box and a filter bag or stocking attached with rubber bands. The stocking or bag must be checked regularly and replaced when full.
Once coarse filtered, greywater can be treated using a sand filter. The basic structure is a waterproof box filled with coarse sand laid over a gravel bed. Greywater flows in at the top and out the bottom. A number of commercial sand filters are available.
Reed beds and sand filters treat the wastewater through filtration and some biological nutrient uptake. Wastewater needs to be pre-treated to allow removal of large particles, otherwise clogging will occur, and the lifetime of the system will be reduced.
Smaller sized aerated wastewater treatment systems are also suitable for treating greywater for general re-use.

REUSING WASTEWATER OUTDOORS

Reusing wastewater outdoors can reduce your household's potable water use by 30 to 50 percent.
Treated wastewater can be re-used to water gardens either by subsurface or above ground irrigation. Only treated and disinfected wastewater should be used for above ground irrigation due to potential presence of pathogens.
The only place where blackwater can be safely re-used is outdoors. However, in some States blackwater cannot be re-used for above ground irrigation even if treated and disinfected: check with your local council or state health department.

PRECAUTIONS

Avoid watering fruits and vegetables with re-use water if they will be eaten raw. There is a chance that pathogenic organisms may be present in wastewater even after treatment.

The level of re-use of wastewater in the garden needs to be balanced with the amount of water, solids and nutrients that the plants and soil in your garden can absorb. If excess wastewater is applied:

* Excess nutrients may run-off or leach through the soil to enter waterways, contributing to algal blooms and other water quality problems.
* Soils and plants may become water logged and inhibit plant growth.
* Soils can become physically clogged with organic and suspended material or damaged by salts in the wastewater.

TREATMENT SYSTEMS FOR OUTDOOR RE-USE

There are many different types of treatment systems suitable for outdoor re-use, a few examples are given below.

Wet composting systems treat all household wastewater and also allow the composting of other household organic wastes (kitchen and green waste). Compost must be removed periodically and disposed of carefully underground. The effluent from wet composting systems typically requires further treatment and/or disinfection if it is to be re-used above ground.

WET WEATHER STORAGE

If you are reusing your wastewater in the garden, you will need to have a method of either disposing or storing the wastewater you do not require during periods of high rainfall.
If storage is not an option and you live in an urban area, excess wastewater can be directed to a sewer. In rural areas sub-surface disposal to a trench in the garden is recommended, provided there is enough space.
Storage is recommended as it maximises the usefulness of wastewater.

Wastewater should be treated and disinfected before storage. Storage requirements depend on:

* Climate.
* Household demand for re-use water.
* Presence/size of disposal area.
* Maximum daily wastewater output.

Stormwater is pure rainwater plus anything the rain carries along with it. Stormwater should be considered a valuable resource. Its re-use leads to water savings and reduced environmental impact.

In urban areas stormwater is generated by rain runoff from roof, roads, driveways, footpaths and other impervious or hard surfaces. The stormwater system is separate from the sewer system. Unlike sewage, stormwater is generally not treated before being discharged to waterways and the sea.

Poorly managed stormwater can cause problems on and offsite through erosion and the transportation of nutrients, chemical pollutants and sediments to waterways. Stormwater is a useful resource that can replace imported water for uses where high quality water is not required, such as garden watering.Stormwater Management

There are a number of steps the homeowner can take to better manage stormwater, and reduce the environmental impact of their home.

Avoid cut and fill on your block when preparing the building foundations. Attempt to maintain the existing topography and drainage pattern.
Retain vegetation, particularly deep-rooted trees. These lower the water table, bind the soil, filter nutrients, decrease run-off velocities, capture sediment and reduce the potential for dryland salinity.
Detain stormwater on your block where practicable through use of permeable paving, pebble paths, infiltration trenches, soakwells, lawn, garden areas and swales.
Reduce erosion potential on site during building works by minimising the time that land is left in an exposed, unstable condition. Employ sediment traps and divert 'clean' stormwater around the disturbed site.
Minimise the area of impervious surfaces such as paved areas, roofs and concrete driveways.
Grade impervious surfaces, such as driveways, during construction to drain to vegetated areas.
Harvest and store roof water for use.
Reduce pollution resulting from fertiliser, herbicide and pesticide application. Do not over-use products. Follow the manufacturer's instructions regarding amount and frequency of application. Look for organic alternatives.
Avoid the use of solvent based paints. When using water based paints, clean brushes and equipment on a lawn area to trap contaminants before they reach waterways. Plant based paints are the most environmentally benign.

THE TRADITIONAL APPROACH

PIPES

The traditional stormwater management response relied on conveyancing. Water was conveyed by a pipe or channel from a collection area to a discharge point. The collection area is your house or street and the discharge point is the nearest ocean, river or lake. The coveyancing system sought to remove the most water (high quantity) from a site in the shortest time possible (high velocity). Large, impervious paved areas and big pipes are typical of coveyancing.

The traditional system of conveyancing is highly effective in reducing stormwater nuisance and flooding on site, unless the pipes get blocked. Conveyancing does not solve the problem but merely transfers it to the other end of the pipe and ultimately upsets the local water balance. Stormwater is carried rapidly with its suspended litter, oil, sediment and nutrients and dumped in an ocean, river or lake. The receiving waterbody then becomes flooded and temporarily polluted because all the stormwater arrives at one time.