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ENVIRONMENTAL GUIDELINES USE OF EFFLUENT BY IRRIGATION ENVIRONMENTAL GUIDELINES

ENVIRONMENTAL GUIDELINES USE OF EFFLUENT BY IRRIGATION ENVIRONMENTAL GUIDELINES USE OF EFFLUENT BY IRRIGATION From 24 September 2003 the Department of Environment and Conservation (DEC) incorporates the Environment Protection Authority (EPA), which is established in the Protection of the Environment Administration Act 1991 as the Authority responsible for administering the Protection of the Environment Operations Act 1997 (POEO Act). Statutory functions and powers in the POEO Act continue to be exercised in the name of the EPA. Published by: Department of Environment and Conservation (NSW) 59–61 Goulburn Street Sydney PO Box A290 Sydney South 1232 Phone: (02) 9995 5000 (switchboard) Phone: 131 555 (information & publications requests) TTY: (02) 9211 4723 Fax: (02) 9995 5999 Email: info@environment.nsw.gov.au Website: www.environment.nsw.gov.au The Department of Environment and Conservation (NSW) is pleased to allow this material to be reproduced in whole or in part, provided the meaning is unchanged and its source, publisher and authorship are acknowledged. ISBN 1 74137 076 0 October 2004 DEC 2004/87 Printed on recycled paper Foreword Water recycling is becoming a critical element for managing our water resources. By safely irrigating recycled water, sustainable development can be achieved while conserving our high quality water supplies. Being able to access alternative safe water sources is particularly critical in times of drought. By providing an additional source of water, recycling can help to decrease the diversion of water from sensitive river and wetland ecosystems. Another major benefit of effluent reuse by irrigation is the decrease in wastewater discharges to natural waterways. When pollutant discharges to waterways are removed or reduced, the pollutant loadings to these waters are decreased. Substances that can be pollutants when discharged to waterways can be beneficially reused for irrigation. For example, plant nutrients such as nitrogen and phosphorus can stimulate harmful algal blooms in waterways but are a valuable fertiliser for crops. In some cases, returning well treated water to rivers might provide a better outcome than reuse by irrigation, for example, to supplement river flows. This Guideline will however help increase the options available for water management, particularly those sources of wastewater that are not suitable or adequately treated for safe discharge to our rivers, estuaries and oceans. Many water needs can be satisfied with recycled water as long as it is adequately treated to ensure water quality is appropriate for the proposed use. Greater treatment and management is required for uses where there is a greater chance of human exposure to the recycled water. Effluent can pose environmental, public health or agricultural resource risks if not managed appropriately and the information in this Guideline will support the establishment of safe effluent irrigation reuse schemes. Water recycling has proven to be effective and successful in creating a new and reliable water supply, while not compromising public health. Effluent reuse by irrigation is now an accepted practice that will play a greater role in our overall water supply in the future. The NSW Government is committed to encouraging and optimising the safe reuse of water. This Guideline will provide an essential information resource to help meet these goals and promote the wise use of our limited water resources. Bob Debus Minister for the Environment iv Contents Foreword ...................................................................................................................iii Figures and Tables.............................................................................................................viii Symbols and Abbreviations................................................................................................ix Executive Summary ...............................................................................................................x 1. Introduction................................................................................................................1 1.1 Purpose and scope...........................................................................................................1 Application of this Guideline....................................................................................................... 2 Related documents ........................................................................................................................ 3 1.2 Environmental performance objectives........................................................................4 1.3 Uses of effluent in irrigation...........................................................................................5 1.4 Guidance............................................................................................................................5 1.5 How this Guideline is organised...................................................................................6 1.6 Procedure checklist for establishing a system.............................................................6 Planning........................................................................................................................................... 6 Site selection.................................................................................................................................... 6 Design .............................................................................................................................................. 6 Statutory requirements ................................................................................................................. 7 Installation....................................................................................................................................... 7 Operation and maintenance......................................................................................................... 7 2. Site Considerations...................................................................................................8 2.1 Land use conflicts.............................................................................................................8 2.2 Selecting the site...............................................................................................................8 Climate............................................................................................................................................. 8 Preliminary investigations............................................................................................................ 8 Detailed soil investigations........................................................................................................... 9 2.3 Soil properties.................................................................................................................10 Soil sodicity................................................................................................................................... 10 Soil salinity.................................................................................................................................... 10 Saturated hydraulic conductivity.............................................................................................. 11 Available water holding capacity.............................................................................................. 11 Soil pH ........................................................................................................................................... 11 Cation exchange capacity and exchangeable cations............................................................. 11 Emerson Aggregate Test (EAT)................................................................................................. 12 Soil phosphorus adsorption ....................................................................................................... 12 2.4 Soil organic matter.........................................................................................................13 2.5 Acid sulfate soils ............................................................................................................13 2.6 Groundwater ..................................................................................................................15 Groundwater vulnerability ........................................................................................................ 15 2.7 Surface water ..................................................................................................................16 2.8 Flood potential................................................................................................................17 v 3. Effluent Quality and Irrigation Considerations................................................18 3.1 Classification of effluent for environmental management......................................18 3.2 Organic content..............................................................................................................20 3.3 Solids................................................................................................................................20 3.4 Nutrients..........................................................................................................................21 Nitrogen......................................................................................................................................... 21 Phosphorus ................................................................................................................................... 22 Potassium ...................................................................................................................................... 23 3.5 pH.....................................................................................................................................23 3.6 Chemical contaminants.................................................................................................23 Metals............................................................................................................................................. 24 Synthetic organic compounds.................................................................................................... 25 Herbicides ..................................................................................................................................... 26 3.7 Mineral salts....................................................................................................................26 3.8 Specific ions.....................................................................................................................28 Sodium........................................................................................................................................... 28 Chloride and chlorine.................................................................................................................. 29 Alkalinity....................................................................................................................................... 30 Bicarbonate.................................................................................................................................... 30 Boron.............................................................................................................................................. 30 Fluoride.......................................................................................................................................... 30 3.9 Oil and grease.................................................................................................................31 3.10 Treatment and disinfection ..........................................................................................31 Municipal sewage effluent ......................................................................................................... 32 Other effluent types..................................................................................................................... 32 3.11 Other factors....................................................................................................................33 4. Design Considerations...........................................................................................34 Licensing considerations in the design process......................................................................34 Load-based licensing ..................................................................................................................34 The use of models in design ......................................................................................................35 Other design considerations....................................................................................................... 35 4.1 Calculating land area and storage requirements......................................................35 Full reuse schemes....................................................................................................................... 35 Partial reuse schemes................................................................................................................... 36 4.2 The water balance ..........................................................................................................36 Precipitation.................................................................................................................................. 36 Effluent applied............................................................................................................................ 37 Evapotranspiration...................................................................................................................... 37 Percolation..................................................................................................................................... 38 Runoff ............................................................................................................................................ 39 Effluent storage............................................................................................................................. 39 4.3 Nutrient loading rates...................................................................................................40 Nitrogen balance.......................................................................................................................... 42 Phosphorus compounds............................................................................................................. 44 Nutrient imbalances .................................................................................................................... 47 vi 4.4 Salinity control and salt balances ................................................................................48 Soil salinity and plant growth.................................................................................................... 48 4.5 Organic Loading Rates..................................................................................................51 4.6 Heavy metals and persistent organic chemicals.......................................................51 Herbicides ..................................................................................................................................... 55 4.7 Models .............................................................................................................................55 The DEC model............................................................................................................................ 57 4.8 Plant selection and land use.........................................................................................58 4.9 Erosion control................................................................................................................58 4.10 Separation distances and management of buffer zones..........................................58 4.11 Irrigation..........................................................................................................................62 Methods......................................................................................................................................... 62 Suitable irrigation areas .............................................................................................................. 63 Irrigation scheduling ................................................................................................................... 63 Storage management................................................................................................................... 64 5. Operation and Management Considerations.....................................................65 5.1 Site management plans.................................................................................................65 5.2 Control systems..............................................................................................................66 5.3 Monitoring systems.......................................................................................................67 Frequency of sampling................................................................................................................ 68 Effluent .......................................................................................................................................... 69 Soil.................................................................................................................................................. 70 Surface waters............................................................................................................................... 72 Groundwater ................................................................................................................................ 73 Plants.............................................................................................................................................. 73 Animals.......................................................................................................................................... 74 5.4 Tailwater and stormwater runoff control ..................................................................74 Uncontaminated runoff diversion............................................................................................. 74 Contaminated runoff collection................................................................................................. 74 5.5 Site access ........................................................................................................................75 5.6 Occupational health and safety issues........................................................................76 5.7 Plant and animal health................................................................................................76 5.8 Reporting on scheme performance.............................................................................78 5.9 Transfer of effluent to other users...............................................................................78 6. Statutory Requirements.........................................................................................79 6.1 Environment Protection Licences................................................................................79 Background................................................................................................................................... 79 When is a licence required?........................................................................................................ 80 Assessing a licence application.................................................................................................. 81 Information to be included when applying for a licence....................................................... 82 Licence conditions........................................................................................................................ 86 6.2 Environmental offences ................................................................................................86 vii 6.3 Development consent....................................................................................................86 Part 4 of the EP&A Act................................................................................................................ 87 Integrated development assessment (IDA) ............................................................................. 87 Part 5 of the EP&A Act................................................................................................................ 87 Examples ....................................................................................................................................... 88 6.4 Other statutory requirements ......................................................................................89 Sewerage schemes managed by local government ................................................................ 89 Activities within national parks................................................................................................. 89 Threatened species....................................................................................................................... 89 Protection of drinking water supplies ...................................................................................... 90 Animals to abattoirs..................................................................................................................... 90 Pure food legislation.................................................................................................................... 91 Australian and New Zealand Joint Food Standards Code.................................................... 91 7. References and Further Reading..........................................................................92 7.1 References........................................................................................................................92 7.2 Further reading...............................................................................................................95 Soils, site suitability and planning............................................................................................. 95 Plant water and nutrient requirements .................................................................................... 95 Sewage effluent ............................................................................................................................ 95 Other .............................................................................................................................................. 95 Glossary .................................................................................................................................97 Appendix 1: Guidelines for the Use of Reclaimed Water from Municipal Sewage Treatment Plants...............................................105 Appendix 2: Load-based Licensing .........................................................................108 Appendix 3: Soil Texture Factors for Soil Salinity Measurement.....................109 Appendix 4: The Effluent Reuse Irrigation Model (ERIM)................................110 Model description .....................................................................................................................110 Model assumptions...................................................................................................................111 Decisions.....................................................................................................................................111 Modelling method ..................................................................................................................... 111 Model time step.......................................................................................................................... 112 Percolation................................................................................................................................... 113 Capacity independent solution method................................................................................. 113 Crop factors................................................................................................................................. 114 Rainfall runoff and terminal pond sizing............................................................................... 114 Evaporation, rainfall and the storage pond........................................................................... 114 Discounting rainfall for tree canopy interception................................................................. 115 Discounting irrigation for spray misting................................................................................ 115 Wet weather augmented flows................................................................................................ 115 Method of characterising schemes.......................................................................................... 116 Precautionary discharges.......................................................................................................... 116 Formal model specification ...................................................................................................... 117 Appendix 5: Government Agency Roles................................................................119 Appendix 6: Department of Environment and Conservation Offices..............121 viii Figures and Tables Table 2.1: Landform requirements for effluent irrigation systems.................................13 Table 2.2: Typical soil characteristics for effluent irrigation systems.............................14 Table 3.1: Classification of effluent for environmental management ............................19 Table 3.2: Mineralisation of organic nitrogen in wastewater sludge and effluent in soil................................................................................................22 Table 3.3: Trigger values for metals in irrigation effluent for long term use on all soil types (up to 100 years) .......................................25 Table 3.4: General irrigation water salinity ratings based on electrical conductivity.........................................................................27 Figure 3.1: Relationship between SAR and EC of irrigation water for prediction of soil structural stability............................................................29 Table 4.1: Crop factors for some crops, trees and pasture................................................37 Table 4.2: Yield and nutrient content of crops in NSW for cultivation under irrigation with effluent...................................................41 Table 4.3: Phosphorus adsorption potential of NSW soils (1m depth)..........................47 Table 4.4: Yield reduction of crops due to soil salinity.....................................................49 Table 4.5: Yield reduction of trees due to soil salinity......................................................50 Table 4.6: Maximum permitted topsoil concentration for chemical contaminants ..................................................................................53 Table 4.7: Concentrations of herbicides in irrigation effluent at which crop injury may occur..........................................................................55 Table 4.8 Sensitive receptors of effluent irrigation schemes...........................................60 Table 4.9: Recommended buffer distances to water resources and public areas.........61 Table 5.1: Recommended effluent sampling frequency...................................................70 Table 5.2: Recommended soil monitoring strategy...........................................................72 Table 6.1: Design parameters for effluent irrigation systems..........................................85 Table A1: Guidelines for treatment, disinfection and irrigation controls for the spray application of municipal sewage effluent...............................105 Table A3: Soil texture factors for converting EC 1:5 soil-water solution measurement to saturated extract....................................................................109 Table A5: Summary of key agency regulatory and advisory roles..............................119 ix Symbols and Abbreviations ABM Australian Bureau of uploads/Litterature/ eff-guide.pdf