whether land is irrigated with recycled water or not. Phosphorus loads in runoff from agricultural and urban land can exceed quality parameters for protecting waterways. Intentional discharges of recycled water to stormwater systems, such as from road washing, must assess the nitrogen concentration of the recycled water relative to the receiving water bodies of that stormwater. Management strategies are aimed at reducing loads and preventing movement off-site. Recycled water storages (reservoirs, dams and tanks) can also suffer from excessive algal growth from eutrophication. In addition to production of toxins, algae in recycled waters may clog irrigation systems. Preventive measures include source control, hazard reduction, irrigation tools and light reduction. Various measures can be used to reduce the residual risk of eutrophication of waterways from phosphorus to acceptable levels (see Table A4.12). Table A4.12 Phosphorus eutrophication of waterways: control points, preventive — measures, target criteria and verification Critical control points Preventive measures Target criteria Verification Phosphorus Soil Buffer distances and strips concentrations in Discharges to surface Irrigation with recycled water should nearby surface waters waters minimised not be conducted directly adjacent to have not increased surface waters. Appropriate buffer from baseline levels distances need to be observed and Local waterways taken before buffer plantings used to strip nutrients down slope of development of the from runoff. Buffer distances and recycled irrigation reuse scheme. extent of nutrient stripping devices systems are will depend on slope and the buffered from importance and sensitivity of the runoff to local waterway (Appendix 6). waterways. surface waters is inevitable. Minimise Irrigating and phosphorus loads by not applying fertilisation excess. Also, minimise phosphorus loads by reducing recycled water applied or fertilisers Phosphorus applied. Ensure crop nutrient budget concentration low Phosphorus includes inputs from all sources (water, enough to limit algal concentration limits fertilisers, soils, manures, etc). growth. No algal algae growth Water treatment blooms observed. Fish and other animals can strip Storage Phosphorus loads nutrients from the water column. systems in crops, pastures, parks and gardens Nutrients supply balance with demand are no more than Nutrient from plants grown required for target balance productivity. Some runoff to Irrigation Irrigation tools Reduce residence time of water in storage, increasing the turnover rate in storages, reducing the time available for algal growth and producing conditions unsuitable for algal growth. Algae number low enough to prevent irrigation issues Algal growth controlled. No irrigation emitters and filters blocked.
whether land is irrigated with recycled water or not. Phosphorus loads in runoff from agricultural and urban land can exceed quality parameters for protecting waterways. Intentional discharges of recycled water to stormwater systems, such as from road washing, must assess the nitrogen concentration of the recycled water relative to the receiving water bodies of that stormwater. Management strategies are aimed at reducing loads and preventing movement off-site. Recycled water storages (reservoirs, dams and tanks) can also suffer from excessive algal growth from eutrophication. In addition to production of toxins, algae in recycled waters may clog irrigation systems. Preventive measures include source control, hazard reduction, irrigation tools and light reduction. Various measures can be used to reduce the residual risk of eutrophication of waterways from phosphorus to acceptable levels (see Table A4.12). Table A4.12 Phosphorus — eutrophication of waterways: control points, preventive measures, target criteria and verification Critical control points Preventive measures Target criteria Verification Soil Buffer distances and strips Irrigation with recycled water should not be conducted directly adjacent to surface waters. Appropriate buffer distances need to be observed and buffer plantings used to strip nutrients from runoff. Buffer distances and extent of nutrient stripping devices will depend on slope and the importance and sensitivity of the waterway (Appendix 6). Discharges to surface waters minimised Local waterways down slope of recycled irrigation systems are buffered from runoff to local waterways. Phosphorus concentrations in nearby surface waters have not increased from baseline levels taken before development of the reuse scheme. Irrigating and fertilisation Storage systems Nutrient balance Some runoff to surface waters is inevitable. Minimise phosphorus loads by not applying excess. Also, minimise phosphorus loads by reducing recycled water applied or fertilisers applied. Ensure crop nutrient budget includes inputs from all sources (water, fertilisers, soils, manures, etc). Water treatment Fish and other animals can strip nutrients from the water column. Nutrients supply balance with demand from plants grown Phosphorus concentration limits algae growth Phosphorus loads in crops, pastures, parks and gardens are no more than required for target productivity. Phosphorus concentration low enough to limit algal growth. No algal blooms observed. Irrigation Irrigation tools Reduce residence time of water in storage, increasing the turnover rate in storages, reducing the time available for algal growth and producing conditions unsuitable for algal growth. Algae number low enough to prevent irrigation issues Algal growth controlled. No irrigation emitters and filters blocked.