Return to AGCSA.com.au

AGCSA Water Management

Reclaimed Water

 Please click here to return to Water Management Page

 

     
 

 2.3 RECLAIMED WASTEWATER 

KEY CONCEPTS 

  • Effluent is an excellent source of water if it is of satisfactory quality for the intended purpose.
  • The salts, nutrients etc. in effluent can be beneficial, but in excess they pose a significant environmental risk.
  • Reuse of effluent must be sustainable in the long term. Excessive concentrations of nutrients, salts, heavy metals and other contaminants can cause rapid and severe deterioration of soils, turf quality and water bodies.
  • With careful planning, good understanding of the interactions between effluent and the site, good water and nutrient management and an appropriate monitoring program, effluent can be a useful resource that saves fresh water and reduces fertiliser use.  

 

Reclaimed wastewater, which is primarily treated sewage effluent, is increasingly being used to irrigate turf. A number of detailed reports (Lang et al. 1977; GHD 1977; NSW Task Force on Reclaimed Water 1982) have investigated and described the feasibility of reusing treated sewage effluent. A Department of Resources and Energy report (1983) stated that in Australia the total amount of treated sewage was about 1300 gigalitres/annum, of which 56 gigalitres/annum (4.4%) is reused in irrigation. Treated wastewater is an important water resource for irrigation purposes and in the future it may be the only source of supplemental water available for turf culture.

In regions serviced by Sydney Water, annual usage of recycled water has settled at an average of approximately 27 megalitres per day over the past four years. Recycling within sewage treatment plants (STPs) accounted for 89% of all recycling, irrigation for 10% and industrial recycling for 1%. The present level is about 2% of daily water consumption (Sydney Water 2001).

As demands on our water supplies for domestic consumption increase, less water becomes available for irrigation purposes. However, the increase in urban development brings not only a greater demand for potable waters but also generation of more wastewater. The treatment of this wastewater and its disposal have become significant environmental issues. In particular, the disposal or reuse of wastewater must be done in an ecologically sustainable manner. Wastewater can contain a range of contaminants including salts, nutrients, heavy metals, viruses and bacteria that can limit the reuse options. The use of wastewater that has a heavy contaminant load can have implications for human health, cause soil degradation and result in uncontrolled discharge of pollutants to surface and groundwaters. The other important component of the sustainability equation is maintaining the playing quality of the turf area.

The reuse of wastewater will, in the future, be an integral part of ecologically sustainable development and integrated catchment management philosophies concerning water quality. There is now strong encouragement to reuse treated wastewater for irrigation purposes in order to protect the quality of surface waters. In most states, environment protection policies demand that wastewater no longer be discharged to surface waters and that it be reused. The general philosophy and, in some cases, legislation demand there be no discharge of wastewater to waterways by early in the new millennium. As a consequence, numerous reuse schemes are being established around Australia to use wastewater for turf irrigation.

The reuse of wastewater has a strong community appeal and it seems to be the right thing to do. However, if a reuse scheme is to be sustainable for a long period-and most authorities define this as at least 50 years-then much investigation is required before the scheme is implemented. Once the scheme is implemented, it must then be monitored by the water authority, environmental regulators and the golf course to ensure that it is sustainable and does not present an environmental or public health risk.

2.3.1 Guidelines for the reuse of reclaimed wastewater

Most of the state authorities responsible for the reuse of wastewater, such as the NSW Environment Protection Authority (EPA) and the various state health authorities, have in conjunction with Departments of Agriculture and water authorities produced guidelines for wastewater reuse. While State guidelines vary, the underlying philosophies are similar and most use the ANZECC and ARMCANZ (2000) water quality guidelines and for sewerage effluent, the ANZECC, ARMCANZ and NHMRC (2000): Guidelines for sewerage systems - use of reclaimed water as their base documents. In NSW, the reuse of treated wastewater is covered in the Draft Environmental Guidelines for Industry - The Utilisation of Treated Effluent by Irrigation (NSW EPA 1995).  The following information provides a general overview of this document from a turf management perspective.

2.3.2 NSW guidelines for use of effluent by irrigation

The EPA's Draft Environmental Guideline The Utilisation of Treated Effluent by Irrigation (NSW EPA 1995), is the principal reference and should always be consulted for detailed guidance on irrigating effluent.

The EPA guideline is educational and advisory in nature and can be described as outcome- or performance-based, encouraging best management practices. This means that the guideline describes environmental outcomes (which may be required by legislation or government policy) and provides information on some of the acceptable approaches that may be used to achieve those outcomes. This gives the user the flexibility to develop other approaches specific to their site that meet the environmental outcomes described in the guideline. The guideline is not a mandatory or regulatory tool but is designed to assist the user  to achieve a sustainable effluent irrigation scheme.   The topics that the guideline includes are described below.
 
Scope of the guidelines
The guideline provides information for planners, designers, installers and operators of effluent irrigation systems, with the aims of:

  • encouraging the beneficial use of effluents and providing guidance as to how this might be accomplished in an ecologically sustainable manner;
  • providing guidance for the planning, design, operation and monitoring of effluent irrigation systems in order to minimise risks to public health, the environment and agricultural resources; and
  • outlining the statutory requirements that may be needed for an effluent irrigation system in NSW.

The document is an environmental guideline, it is not a design and operations manual.  Technical and scientific problems associated with the use of effluent can be complex and often require the integrated efforts of several disciplines in science and engineering.  Accordingly, designers and operators might need to seek advice from specialist consultants and from government authorities such as NSW Agriculture, the Department of Land and Water Conservation, NSW Health and Workcover Authority.

Environmental performance objectives
The EPA has established the following environmental performance objectives for using effluent by irrigation.
Resource use: Potential resources in effluent, such as water, plant nutrients and organic matter, should be identified, and agronomic systems developed and implemented for their effective use.
Prevention of public health risks: The effluent irrigation scheme should be sited, designed, constructed and operated so as not to compromise public health.  In this regard, special consideration should be given to the provision of barriers that prevent human exposure to pathogens and contaminants.
Protection of surface waters: Effluent irrigation systems should be located, designed, constructed and operated so that surface waters do not become contaminated by any flow from irrigation areas, including effluent, rainfall run-off, contaminated sub-surface flows or contaminated groundwater.
Protection of groundwater: Effluent irrigation areas and systems should be located, designed, constructed and operated so that the current or future beneficial uses of groundwater do not diminish as a result of contamination by the effluent or run-off from the irrigation scheme or changing water tables.
Protection of lands: An effluent irrigation system should be ecologically sustainable.  In particular, it should maintain or improve the capacity of the land to grow plants, and should result in no deterioration of land quality through soil structure degradation, salinisation, waterlogging, chemical contamination or soil erosion.
Community amenity:The effluent irrigation system should be located, designed, constructed and operated to avoid unreasonable interference with any commercial activity or the comfortable enjoyment of life and property off-site, and where possible to add to the amenity.  In this regard, special consideration should be given to odour, dust, insects and noise.
Protection of plant and animal health: Design and management of effluent irrigation systems should not compromise the health and productivity of plants, domestic animals, wildlife and the aquatic ecosystem. Risk management procedures should avoid or manage the impacts of pathogenic micro-organisms, biologically active chemicals, nutrients and oxygen depleting substances.

Planning and approvals
Users of effluent irrigation may have specific statutory obligations under health, environmental, agricultural and/or food legislation in NSW and these may be a condition of land development.  In addition, wastewater treatment plant owners, operators and end-users may be liable under common law and under the Trade Practices Act for the use of effluent that causes harm. Proposals for an effluent irrigation system should be discussed at the early planning stage with the relevant regulatory or advisory authorities which may include the local council, NSW EPA, NSW Health, NSW Agriculture, Department of Land and Water Conservation, Planning NSW and the NSW WorkCover Authority.

Environment Protection Licences
Specific activities and premises are required to be licensed under the Protection of the Environment Operations Act 1997 (the POEO Act); however, an environment protection licence is not likely to be required for effluent irrigation schemes operating in accordance with the EPA guideline.

Scheduled activities
Schedule 1 of the POEO Act is the 'Schedule of EPA-licensed activities.' A licence is always required for Scheduled activities. Whenever effluent irrigation is ancillary to a Scheduled activity, the licence associated with the scheduled activity may also include conditions relating to the effluent irrigation.

Under the POEO Act, the EPA is the relevant authority for an activity whenever:

  • the activity is listed on Schedule 1 of the POEO Act;
  • a licence to control water pollution from the activity has been granted; or 
  • a public authority is carrying out the activity or is occupying the premises where the activity occurs.

Effluent irrigation is not specifically listed on Schedule 1, therefore it does not generally have to be licensed.

Non-scheduled activities
Non-scheduled activities are any activities other than those listed in the 'Schedule of EPA-licensed activities.' The POEO Act does not generally require non-scheduled activities, which includes effluent irrigation, to be licensed. Operators of effluent irrigation schemes should be able to manage their effluent to avoid pollution of water.

Golf courses
Golf course construction and operation is a non-scheduled activity and therefore does not generally require an environment protection licence.  The local council will be the appropriate regulatory authority for golf courses.

Site assessment
Where reclaimed water is to be used as a source of irrigation water it is very important that a detailed analysis and site investigation are undertaken as part of the planning process.
Site assessments for golf courses must look in detail at all greens, tees and fairways, soil types and all other areas to be irrigated with effluent.

ESSENTIAL SITE ASSESSMENT CRITERIA 

  • Soil types and soil limitations for irrigation of effluent (including phosphorus sorption capacity, exchangeable sodium percentage, soil salinity, depth to seasonal high water table, depth to bedrock or hardpan, saturated hydraulic conductivity; available water capacity, soil pH (CaCl2), effective cation exchange capacity, emerson aggregate test).
  • Limiting site characteristics (including drainage, climate, proximity and sensitivity of ground and surface waters, topography, geology of the site; proximity to dwellings or other sensitive receptors, flooding potential)
  • Grass species
  • Irrigation requirements and methods
  • Nutrient loads
  • Ability of the site to cope with extra demands because of the effluent, e.g. extra growth, runoff containment.
  • Proximity to dwellings  

 

Reclaimed water treatment
Effluent may include water from industrial sources, stormwater runoff and sewage. The quality of the  effluent depends on its source and level of treatment. For reclaimed water from sewerage systems, effluent quality also depends on the catchment and industries serviced. Treatment must be such that it protects the beneficial uses of soil, ground and surface waters from polluted runoff and protects public health from toxicants and micro-organisms.

A priority performance objective for effluent reuse is protection of human health. In general, the better the treatment and the greater the disinfection, the fewer micro-organisms there will be and therefore there are fewer restrictions to site access and management. For example, tertiary or advanced treatment of sewerage wastewater will produce an effluent that is very low in biological oxygen demand (BOD), suspended solids (SS), coliform bacteria and viruses and the wastewater can be used for food crops or aquaculture  with fewer controls on human access to the irrigated area.
 
For irrigation of reclaimed water from sewerage systems, public health requirements are based on national Guidelines for Sewage Systems-Reclaimed Water (ARMCANZ, ANZECC & NHMRC 2000). This national guideline outlines general treatment, disinfection and irrigation requirements, however, in NSW the NSW EPA or NSW Health may adopt more stringent requirements on a site-specific basis.
NSW Health should be consulted in regard to the level of treatment of effluent to be achieved when public health could be at risk through contact with irrigated effluent.

Golf courses
For golf courses, the relevant end-use category in the national sewerage reclaimed water guidelines is: "URBAN (NON POTABLE) - Municipal with either controlled or uncontrolled public access"

Nutrients, salts and heavy metals are recognised as important constituents of wastewater and must be accounted for in determining the sustainability of a reuse site.

Reclaimed water quality for irrigating turf
The quality of irrigation waters has already been  outlined in Section 2.2.  The EPA effluent irrigation guideline provides a detailed description of the key constituents of reclaimed wastewater and how effluent quality should be considered in the design and operation of an irrigation system. Summary information on key effluent constituents with emphasis on turf irrigation is provided below.

  • Nitrogen: In wastewater nitrogen levels can be very high and the main impact of this will be on grass growth. Every time the turf is irrigated it is fertilised with a soluble source of nitrogen that is readily taken up by the plant. Uncontrolled and lush growth can occur, resulting in a soft, thatchy and disease-prone turf. Nitrogen that enters waterways can also stimulate growth of nuisance plants and weeds and algae.
  • Phosphorus: Phosphorus is another important element and applications in excess of what the soil can absorb and the vegetation will take up can be leached into ground and surface waters. Excess phosphorus in waterways is a prime cause of algae growth.
  • Heavy metals: Heavy metals such as zinc, iron, copper, nickel, lead, chromium and cadmium occur in recycled water. Iron, zinc and copper are essential for healthy turf but in excessive amounts these elements are toxic. Heavy metals in recycled water can be a problem where the main source of effluent is of industrial origin; however, recycled water that is mainly of domestic origin has a low heavy metal input and is unlikely to be toxic to turf. The ANZECC and ARMCANZ (2000) guidelines for irrigation water quality and Harivandi et al. (1997) have published comprehensive lists of heavy metals and the recommended concentrations.
  • Boron: Boron occurs naturally in some soils and groundwater as well as in recycled water. Boron is used in detergents and soaps and most treated effluent contains 0.5-1.0 mg/L of boron. Boron is essential to turf growth but levels greater than 2.0 mg/L can be toxic. The effects of boron depend on plant species tolerance and soil conditions. Well-drained soils that are readily leached generally do not accumulate boron because it is a mobile element and is easily leached through the soil. In general, recycled water of domestic origin does not contain toxic levels of boron.
  • Human pathogens: When dealing with treated wastewater, health considerations must be taken into account. Wastewaters (such as those from sewerage systems) can contain a wide variety of potentially infectious microorganisms . Thermotolerant coliforms are the most commonly used indicator of pathogens.

All states have public health requirements governing the microbiological quality and use of recycled water. These requirements are generally based on the ANZECC, ARMCANZ and NHMRC (2000) reclaimed water guidelines and are designed to provide asistance to authorities, users and the general public. 

  • Other contaminants: Wastewater used for turf irrigation can come from a range of sources and knowledge of what takes place at the source will provide an indication of possible toxic elements, for example:
  • citrus processing-various oils and acids
  • sewerage treatment -eg agricultural and industrial chemicals;
  • petroleum processing-hydrocarbon residues; and
  • wool scouring-sodium and bicarbonate.

Design considerations
The design of an effluent irrigation scheme needs to take into consideration a range of factors including: site limitations, plant selection, volumes of water and levels of pollutants in effluent, irrigation methods and scheduling, land area available for irrigation, storage requirements of effluent; stormwater runoff controls, and buffer distances to sensitive receptors such as waterways.

Water and nutrient budgets
When planning and designing a scheme to use reclaimed wastewater or where it is already in use, it is very important to estimate the annual water requirements and nutrient load as this will have a significant effect on the fertiliser program, soil management and the health and quality of the turf. The calculation of the irrigation requirement is detailed in section 2.6.

The nutrient content is an important economic as well as environmental consideration (Harivandi et al. 1997). Even if the concentration of nutrients is relatively low, because they are applied on a regular basis, the nutrients are efficiently used by the turfgrass.

CALCULATING NITROGEN LOADINGS

Average total nitrogen in the wastewater   =  30 mg/L (0.00003 kg/L)
Evapotranspiration (ET) per irrigation season  =  350 mm
Volume of water applied per 100 m² per season  = 35 000 L
Total nitrogen applied per 100 m² per season = 35 000 L × 0.00003 kg    =       1.05 kg/L 100 m².


If the annual nitrogen requirement is 3kg/100 m², then the reclaimed wastewater will provide about 30% of the annual requirement.

CALCULATING PHOSPHORUS LOADINGS

Average total phosphorus in the wastewater         =  5-10 mg/L (0.000005-0.00001 kg/L)
Evapotranspiration (ET) per irrigation season        =  350 mm
Volume of water applied per 100 m² per season    =  35 000 L
Total phosphorus applied per 100 m² per season  =  35 000 L × 0.000005 kg (0.00001 kg) = 0.175-0.35 kg/L 100 m².

If the annual phosphorus requirement is 0.5-0.8 kg/100 m², then the reclaimed wastewater will provide up to 70% of the annual requirement.

The above examples are for a relatively low ET requirement. If the water demand or usage were 1200 mm (120 000 L), then the nitrogen load would be 3.6 kg/100 m² and the phosphorus 0.6-1.2 kg/100 m². In this scenario, the annual nitrogen requirement is provided by the wastewater, as is all of the phosphorus.

The above examples assume that the irrigation season is over the full 12 months; however, this is not the case in all areas of New South Wales where the climate is more seasonal, with periods when no supplementary water is required. It is important to realise that there is little or no carryover of nitrogen in sandy soils and while the applied nitrogen meets the annual requirements it may in fact be applied over a shorter time period. This can result in excessive, soft growth.

In assessing the suitability of wastewater for irrigating turf, long-term analytical data is required, as the quality of wastewater can change during the year: e.g. in summer the salts often increase. Monthly water quality data, over several years, will give a good indication of the possible changes. Unfortunately, many wastewater treatment plants, in particular those in rural areas, often only have minimal information available.

ESSENTIAL DATA REQUIRED FOR ASSESSING RECLAIMED WATER QUALITY:

pH      Electrical conductivity
Calcium     Magnesium
NH3-N     Total phosphorus
NO2-N     Boron
NO3-N     Potassium
Bicarbonate    Heavy metals
Sodium     Chloride

2.3.3 Site evaluation and monitoring

In evaluating the feasibility of using wastewater, it is important to determine whether or not the system can cope with the potential nutrient and salt loads and whether a long-term, sustainable turf system can be maintained.

There is no point in establishing a recycling system because it seems like a good thing to do if in the long term it is going to result in site degradation. The utilisation of treated
effluent by irrigation (NSW EPA Draft Environmental Guideline) describes the procedure for establishing reclaimed water irrigation system.

Procedure for establishing an effluent irrigation system
The following is a suggested checklist of procedures to be followed when setting up an effluent irrigation system:

Planning:

  • Discuss the proposal with the relevant EPA regional office and other appropriate authorities. 
  • Assess effluent quality

 Site selection:

  • Select an appropriate site and conduct site assessment
  • Any site assessment must look in detail at all greens, tees and fairways and determine the following conditions  

 ESSENTIAL SITE ASSESSMENT CRITERIA
  • Soil types
  • Drainage
  • Phosphorus retention
  • Proximity and quality of ground and surface waters
  • Topography
  • Geology of the site
  • Irrigation requirements
  • Nutrient loads
  • Ability of the site to cope with extra demands because of the waste water e.g. extra growth, runoff containment
  • Proximity to dwellings

Design:

  • Determine the water balance for the irrigation system
  • Establish the minimum land area requirements based on limiting loading rates (hydraulic, nutrient, organic and salt.
  • Calculate the minimum wet weather storage capacity requirements for the irrigation system
  • Define the operational processes to be used in effluent irrigation and management

 Statutory approvals:
• Comply with the requirements of the Local Council, NSW Health, EPA and other authorities in the planning and design stages where appropriate

Installation:

  • Install system in accordance with the conditions of Pollution Control Approval
  • Once construction is completed, forward a Certificate of Compliance to the EPA indicating that installation has been in accordance with the conditions of approval 

Operation and maintenance:
• Operate the system in accordance  with best management practices

On-going monitoring   

An annual review of the management plan and monitoring results may be required as a condition of licence and this may be in the form of an annual Environmental Management Report. These procedures enable the operator and the EPA to assess the on-going performance of the irrigation scheme.

Sampling may be required on the following:

  • Soils (surface and subsoils down to 2 m) from the irrigation areas;
  • Effluent
  • Groundwaters and surface waters
  • Crops/plants 

The samples may need to be analysed for the following constituents, where appropriate:
 Soils: Structure, profile features, cation exchange capacity, electrical conductivity, N and P (total and available), P sorption capacity, organic matter, chloride, and pH.
 Wastewater, and water samples: BOD, N and P (Total and Available), salinity indicators (electrical conductivity, Na, Ca, K, Mg and SAR), exchangeable cations, chloride, chemical contaminants, and TDS.
 Additionally, the water table height should be measured.

Sampling may be necessary where some trace contaminants had previously been identified in the system. Plant analysis also provides the opportunity to fine tune the nutrient budget since it provides quite precise information on nutrient uptake by the vegetation. The frequency of sampling would vary according to the parameter being measured.

Once the site assessment is completed and a reuse program implemented, it is then necessary to initiate a monitoring program. The site assessment will identify key areas that can be used as indicators and include monitoring.

 KEY MONITORING POINTS FOR GOLF COURSES
  • Surface and groundwater
  • Each of the major soil types
• Representative greens, tees and fairways

The monitoring will  include water and soil analysis; water use; weather data and records of any significant changes in turf conditions (e.g. pests, weeds and disease, soft growth etc).

 

Where reclaimed water is to be used as a source of irrigation water it is very important that a detailed analysis and site investigation  are undertaken as part of the planning process.

The following is a basic checklist of tasks that need to be undertaken.

Please click here to return to Water Management Page