"Use of water treatment solids (WTS)"
Use of water treatment solids (WTS) Updated May 2007∗ EPA 188/07: EPA Technical Bulletin Land application of alum sludge from water treatment (November 1996) was withdrawn in March 2001. This interim guideline aims to provide a precautionary approach to the use of WTS until more information becomes available. Introduction Water treatment solids (WTS) are the solid waste products resulting from the treatment of raw water at municipal water treatment plants. Even though WTS generally have little nutrient value, they may be beneficially used as a soil conditioner or agricultural liming agent, depending on the individual characteristics of the product. The Environment Protection Authority (EPA) is investigating the potential environmental risks associated with the use of WTS, and assessing effective strategies to manage these risks. In particular, the EPA is concerned with the possibility of elevated copper levels in WTS, due to the use of copper sulphate at some water treatment plants to control algal blooms during warmer weather. Elevated concentrations of copper in soil (> 200 mg/kg) may create immediate or long- term environmental harm. Furthermore, WTS have the potential to bind plant-available phosphorus in the soil, which may degrade the soil agricultural value. This problem may be mitigated or remediated by adding fertiliser to the soil. Legislation The principal legislation addressing the use of WTS in South Australia is the Environment Protection Act 1993 (the Act). In particular, Section 25 imposes a general environmental duty on all persons using WTS, requiring them to take all reasonable and practicable measures to prevent or minimise any resulting environmental harm. In addition, inappropriate use of WTS may cause either serious or material environmental harm under Sections 79 and 80 of the Act, or environmental nuisance, an offence under Section 82 of the Act. ∗ Updated for ‘Further information’ Use of water treatment solids (WTS) May 2007 Consultation This guideline was prepared by the EPA with the cooperation of the Biosolids Committee, which has representatives from the EPA, SA Water, United Water, United Utilities, Primary Industries and Resources South Australia (PIRSA), Department of Human Services (DHS), and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Interim status To ensure protection of all environmental values and the future economic viability of land uses, further information about WTS is required to support its use. An intensive research project is being undertaken to identify the suitability of WTS for application to cropping or agricultural land. This interim guideline will be replaced at the culmination of that research. Aims of this guideline During the interim period, this guideline: • provides general requirements and guidelines for the use of WTS from the municipal water treatment process, in particular for land application • applies to a specific site or area of land given its current use and does not relate to future land use. Responsibilities It is the responsibility of all generators, handlers and users of WTS to manage the material in a safe and environmentally sound manner, ensuring that: • WTS are not used on land currently under the cultivation of crops intended for direct human consumption • WTS with a copper level greater than 750 mg/kg are not applied to land, other than horse tracks • any site receiving WTS is properly managed to ensure that any potential adverse impact on the environment (including human and animal health) is minimised • the EPA is contacted and made aware of any information relevant to the adverse environmental impact of WTS. Definitions water treatment solids (WTS): the residual solid waste product resulting from the physical, chemical and/or mechanical treatment of raw water at municipal water treatment plants, commonly consisting of highly disordered clay minerals, organic matter, hydroxides of aluminium and iron, and polyelectrolytes agricultural land: land used for the production of crops and/or the raising of livestock land application: spreading material onto land or injecting material below the land surface slope percentage: the percentage of increase or decrease in metres of height for every 100 m of lateral distance pH: the acidity or alkalinity of the soil or WTS, measured in pH units ranging from 1 to 14 where a pH of 1 is highly acidic, 14 is highly alkaline and 7 is neutral Page 2 Use of water treatment solids (WTS) May 2007 conservation value: a value determined through consideration of an area's diversity of habitat, security against development, whether the area abuts an industrial or urban area, its uniqueness in terms of scenic, geological or biological features, and its size and proximity to similar areas stockpiling: storage of material that is not immediately used Guidelines WTS should be used in a manner that does not cause any harm to groundwater or surface waters, or create any dust, noise or odour problems. WTS should not be applied to land in a manner or in amounts that diminish the conservation value of a site, or in amounts which adversely impact on its agricultural use. WTS that are applied to agricultural land other than horse tracks should not exceed the following contaminant levels (equivalent to Grade B Biosolids): Contaminant Level (mg/kg) arsenic 20 cadmium 11 copper 750 lead 300 mercury 9 nickel 145 zinc 1400 Site management Distribution WTS should be applied onto land in a manner that ensures an even distribution of the material, causes no ponding on the surface of the land, and produces no runoff from the site. Vegetation used as forage by any livestock should not be coated or contaminated with WTS, and WTS should not be applied to land currently under cultivation for crops intended for direct human consumption. Interference with the natural habitat of Australian native animal species should be minimised. Rate The application of WTS to land should be at a rate to minimise: • over-application of nitrogen • phosphorus deficiencies • overly alkaline conditions • overloading the soil with heavy metals. Attachment 1 shows a table that can be used to calculate the annual application rate of WTS to agricultural land. Page 3 Use of water treatment solids (WTS) May 2007 Site location Separation distances WTS should not be applied to land: • within 50 m of an occupied dwelling or school • within 20 m of a property boundary • within 100 m of an open watercourse or bore, or in a manner that may potentially lead to groundwater or surface water contamination • where livestock will be grazing, if the copper levels in the WTS exceed 200 mg/kg. Runoff WTS should not be applied to land that has waterlogged soil or a slope greater than 5% unless engineering works are installed to eliminate the risk of contaminated surface runoff. WTS should be incorporated by ploughing into the soil profile (approximately 100–300 mm depth) unless this is counter to the intended use of the area—for example, a horse track—or if ploughing may increase the risk of runoff or soil transport down a slope. pH WTS should not be applied to land with a pH (CaCl2) below 5.5, unless the addition of WTS (in accordance with the site management rate specified below), or any other soil conditioner, will raise the pH of the soil to this level after equilibration with the soil. Furthermore, the soil pH (CaCl2) should be maintained above 5.5 during the land application period and for two years after the application of WTS at the site has ceased. Storage WTS should only be stored at a level site (<5% slope) and for a period of less than six months for any particular batch to prevent potential contamination problems with watercourses, windblown residue, runoff, and livestock access. A storage area should be designed to hold at least the runoff from a one-in-ten-year storm event. These storage guidelines do not apply to processing and storage facilities of a water treatment plant, a landfill site licensed to accept WTS, or WTS in transit to another location, whether by permitted vehicles or by loading, offloading, transporting or handling equipment used in application. References Ahmed M, Grant CD, Oades JM and Tarrant P 1997, Water treatment sludge: potential for use as a soil ameliorant, Urban Water Research Association of Australia, Research report No. 106, 51 pp. Elliott HA and Dempsey BA 1991, Agronomic effects of land application of water treatment sludges, Journal of American Water Works Association, 83 (4), pp 126–131. Moodley M 2001, Effects of the land disposal of water treatment sludge on soil physical quality, PhD Thesis, University of Natal, South Africa. Page 4 Use of water treatment solids (WTS) May 2007 Currency of this guideline This guideline will be updated as new research becomes available. Persons relying on the information should check with the EPA to ensure that it is current at any given time. FURTHER INFORMATION Legislation Legislation may be viewed on the internet at: <www.legislation.sa.gov.au> Copies of legislation are available for purchase from: Service SA Government Legislation Telephone: 13 23 24 Outlet Fax: (08) 8204 1909 101 Grenfell Street Internet: <shop.service.sa.gov.au> Adelaide SA 5000 Email: <firstname.lastname@example.org> For general information please contact: Telephone: (08) 8204 2004 Environment Protection Authority Facsimile: (08) 8124 4670 GPO Box 2607 Freecall (country): 1800 623 445 Adelaide SA 5001 Internet: <www.epa.sa.gov.au> E-mail: <email@example.com> Page 5 Use of water treatment solids (WTS) March 2007 Attachment 1 The maximum rate of WTS application to land should be calculated using the following table (1) (2) (3) (4) (5) (6) (7) (8) Contaminant WTS Maximum Existing Available Annual Maximum Is ANY annual Annual biosolids contaminant permissible soil concentration assimilative assimilative permissible assimilative application rate concentration concentration— in the soil— capacity of capacity of soil annual capacity greater —t/ha —mg/kg mg/kg mg/kg soil mg/kg (10 yrs)—kg/ha contaminant than maximum If (7) = Yes load—kg/ha permissible load? (from Biosolids (from analysis) (2) – (3) (4) × 10 (6) ×1000/(1) Guidelines) (see (5) > (6) Yes or references) No If (7) = No (5) ×1000/(1) Arsenic 20 0.7 Cadmium 3 0.15 Copper 200 12 Lead 200 15 Mercury 1 0.1 Nickel 60 3 Zinc 250 30 Maximum annual application rate (tonnes per hectare) = minimum value column (8) Page 6