Long Term Sludge Experiments - Frequently Asked Questions

Long Term Sewage Sludge Experiments Frequently Asked Questions

1 Why is sewage sludge applied to land? ...... 1 2 How do metals end up in sewage sludge and at what concentrations? 1 3 What else goes down the drain that might end up in sludge? ...... 2 4 What other routes are there for sludge...... 2 5 Why was this experiment set up?...... 3 6 Why have we not seen these effects before now? ...... 3 7 What happens to food crops grown in soil where sludge is applied? ....3 8 How is the use of sewage sludge in agriculture regulated/ controlled? .4 9 How will the results be used?...... 4 10 To what area of land are organic materials applied?...... 4 11 What are the implications of the these results for other organic materials applied to land? ...... 4 12 Will sludge continue to be spread on land?...... 4 13 How is the use of sewage sludge in agriculture regulated/ controlled? .5 13.1 European controls ...... 5 13.2 Sludge (Use in Agriculture) Regulations 1989...... 5 13.3 Cross Compliance ...... 5 13.4 Code of Practice for the Agricultural Use of Sewage Sludge...... 6 13.5 The “Safe Sludge Matrix”...... 7

1 Why is sewage sludge applied to land? sewage sludge onto land can benefit soils in many ways; providing nutrients, stabilising and improving their structure (thus reducing the risk of soil erosion), improving pH, increasing water holding capacity (which helps to reduce flood risk) and locking carbon into the soil. They are a good source of nitrogen, phosphorus and sulphur, and contain magnesium and other useful trace elements. Using sewage sludge as a fertiliser also reduces the need for inorganic fertilisers which are often produced in energy intensive processes. In the UK, over 100,000 hectares are beneficially treated with sewage sludge annually equivalent to 0.8% of the total UK agricultural land area. (England – 8.1 million hectares of agricultural land, UK 12.0 million hectares excluding rough grazing)

Government and the believe that the recycling of sewage sludge on land is the Best Practicable Environmental Option in most circumstances.

2 How do metals end up in sewage sludge and at what concentrations? Metals enter the sewerage system from a number of sources, including domestic and commercial premises, and run-off from impervious areas. Long Term Sewage Sludge Experiments - Frequently Asked Questions

Metals, particularly zinc, are present in many household and personal care products as preservatives and anti-microbial agents. The majority of copper comes from plumbing systems. During the treatment of wastewater, metals tend to associate with solids because of their chemistry (e.g. electro-static charge) and end up in the solid sludge (rather than in the water fraction).

Concentrations of metals in sludge have reduced markedly over the last 10-15 years as a result of strict controls at source and changes in the UK manufacturing base. The main inputs of metals now come from diffuse sources such as run-off and household use rather than industrial sources.

Comparison of metal content (mg metal per kg dry solid sewage sludge) of archived sewage sludge material and currently produced sewage sludge. Metal Archived sewage Currently produced sewage sludges** sludges*** Zinc 6000 608 Cadmium 44 1.4 Copper 5050 300 Lead 1240 138 Nickel n/a 39 Chromium n/a 82 Mercury n/a 1.36 **Late 1970s-early 1980s information **Data for England & Wales 2005 (Source: Ofwat MD109) n/a = not available

3 What else goes down the drain that might end up in sludge? Under the Water Industry Act 1991 (as amended), discharges from all manufacturing sites and many other commercial premises are subject to trade effluent consent conditions that limit the amount of PTEs and other contaminants entering the sewage system. The Urban Water Treatment Regulations 1994 place a statutory duty on sewerage undertakers to exercise a trade effluent function sufficient to ensure that discharges from their treatment plants do not adversely affect the environment and that sludge can be disposed of safely in an environmentally acceptable manner. Water Services Companies monitor these discharges from industry to ensure that the appropriate standards are complied with and can prosecute for breaches of trade effluent consents.

4 What other routes are there for sludge A recent note on “Energy and Sewage” by the Parliamentary Office of Science and Technology states:

“Sludge may … be incinerated, with the option of energy recovery. However, to incinerate sludge, it must be dry enough to burn with no extra energy input other than that needed to fire up the incinerator. It therefore needs dewatering, using energy intensive processes such as centrifugation or thermal dehydration. Centrifugation requires less energy but surplus heat from can be used for thermal dehydration. There has been strong opposition from some sections of the public over incineration of due to fears about impacts on human health. At present, reuse of sludge via application to land is generally considered a more acceptable option. Long Term Sewage Sludge Experiments - Frequently Asked Questions

However, the quantity of sludge produced is increasing while the area of available farmland in the UK is decreasing. This increases energy costs as there is more sludge to be transported, usually via lorry, to more remote locations.“

Recycling sewage sludge to land supplies organic matter and essential plant nutrients.

5 Why was this experiment set up? The “Long-term Sludge Experiments” were started in direct response to the report of an Independent Scientific Committee which, in 1993, recommended that “further research was needed to examine the effects of heavy metals from sewage sludge on soil micro-organisms.” The report also recommended that the sites for the experiment “should provide a long-term resource for use in controlled experiments.” MAFF/DoE (1993). Review of the Rules for Sludge Application to Agricultural Land: Soil Fertility Aspects of Potentially Toxic Elements: Report of the Independent Scientific Committee. The intention of the experiment was to apply sewage sludge at metal loadings which would bring soil metal concentrations up to and in excess of the maximum permissible soil metal limits in the Sludge (Use in Agriculture) Regulations, in order to search for measurable changes, particularly in soil microbial properties.

6 Why have we not seen these effects before now? The experiment was deliberately designed as long-term because soils usually respond slowly and variably to pressures. The first 4 years was a setting-up period; thereafter measurements were taken every other year in 1999, 2001, 2003 and 2005. It was important to accumulate a number of measurements before any conclusions were drawn. Even the conclusions being drawn now, after 12 years, should be regarded as interim. One key question is whether the effects seen to date will persist. Some effects were apparent at the first measurements in 1999 and persisted thereafter, whilst some were only evident in one sampling year. For the reasons stated above, it is important that a sufficient body of data was accumulated before interim conclusions could be drawn.

7 What happens to food crops grown in soil where sludge is applied? With the data provided from the experiments to date, it is not possible to read across directly to other legume crops because the rhizobia may differ in their ability to tolerate Zn. It is unlikely that non-legume (e.g. root crop) yields will be affected, as no consistent yield decreases have been measured in cereal and grass crops at the study sites to date.

Current EU legislative limits on metals in sludge-treated soils are designed not only to protect human health, but crop growth and health as well. In addition, producers using sludge follow The Safe Sludge Matrix guidance developed by scientists, retailers and producers, which prevents the transfer of pathogens to food crops

Long Term Sewage Sludge Experiments - Frequently Asked Questions

8 How is the use of sewage sludge in agriculture regulated/ controlled? Sewage sludge application to land is regulated by the Sludge (Use in Agriculture) Regulations when applied to agricultural land or under an exemption from the Licensing Regulations 1994 when applied to non-agricultural land. These activities are monitored by the Environment Agency in England and Wales and SEPA in Scotland.

9 How will the results be used? The results from the Long-term Sludge Experiments will help to underpin regulation of sludge spreading on agricultural land so that controls are based on sound science. These interim results raise issues that need to be clarified further in the next stage of the study.

10 To what area of land are organic materials applied? Animal manures are applied annually to around 3.5 – 4 million hectares of land in the UK, green to c.20,000 hectares and paper crumble to c.10,000 hectares. Sewage sludge is applied to more than 100,000 hectares annually.

11 What are the implications of the these results for other organic materials applied to land? Other organic materials that are applied to land may also contain heavy metals. However, until further data is available on the bioavailability of metals from other materials, we can't be certain that metals from other sources would have similar impacts on soil function or crop uptake. We do not yet have equivalent data for other materials.

Currently the re-use of waste derived organic materials is controlled through waste regulations, or where compost meets the appropriate standard, through the use of the Quality Protocol for Compost, which takes a precautionary approach in order to ensure benefit to the soil. In either case there is a requirement to measure and then monitor the addition of heavy metals to soils and ensure that soil function is protected.

Agricultural manures may also contain some heavy metals. Where these are used, farmers are expected to comply with the recommendations of the Codes of Good Agricultural Practice now being developed into a revised Code of Good Agricultural Practice for soil, water and air. http://defraweb/corporate/consult/cogap-rev/index.htm

12 Will sludge continue to be spread on land? Yes. Provided sludge spreading is carried out in accordance with good practice guidance, and in the light of a science-based understanding of potential risks, it is a positive recycling activity which can improve soils. The Long-term Sludge Experiments will help contribute to the body of scientific evidence for the safe spreading of sludge on agricultural land. Long Term Sewage Sludge Experiments - Frequently Asked Questions

13 How is the use of sewage sludge in agriculture regulated/ controlled? Sewage sludge application to land is regulated by the Sludge (Use in Agriculture) Regulations when applied to agricultural land or under an exemption from the Waste Management Licensing Regulations 1994 when applied to non-agricultural land. These activities are monitored by the Environment Agency in England and Wales and SEPA in Scotland.

13.1 European controls ¾ The Sewage Sludge Directive 86/278/EEC requires member states to ‘regulate sewage sludge in agriculture in such a way as to prevent harmful effects on soil, vegetation, animals and man, thereby encouraging the correct use of such sewage sludge’ ¾ The Directive lays down maximum metal limits for concentrations of heavy metals in soil and maximum annual quantities (expressed as a 10 year average) which may be introduced into the soil ¾ The Directive was transposed into UK law by way of the Sludge (Use in Agriculture) Regulations 1989. The UK regulations do not set maximum metal concentration limit values in the applied sludge, but instead set maximum concentration limits in soils receiving sludge and maximum annual metal loading rates (as a 10 year average).

13.2 Sludge (Use in Agriculture) Regulations 1989 Requirements of the current Regulations include: ¾ Testing requirements and standards for soil and sludge ¾ Cropping and grazing restrictions following the application of sludge to agricultural land ¾ Records must be kept by sludge producer and occupier of land where sludge is spread ¾ Sludge producers must maintain a sludge register to demonstrate compliance with the requirements of the Regulations

Sludge (Use in Agriculture) Regulations – maximum statutory permissible concentrations of PTEs in soil after application of sewage sludge. Element Soil metal limit (mg of metal per kg of soil) according to the pH of soil 5.0<5.5 5.5<6.0 6.0-7.0 >7.0 Zinc 200 250 300 450 Copper 80 100 135 200 Nickel 50 60 75 110 For pH 5.0 and above Lead 300 n/a n/a n/a Cadmium 3 n/a n/a n/a Mercury 1 n/a n/a n/a

13.3 Cross Compliance Compliance with the Sludge (Use in Agriculture) Regulations is now a Statutory Management Requirement under Cross Compliance. Farmers must Long Term Sewage Sludge Experiments - Frequently Asked Questions comply with the requirements of the Regulations or risk losing a proportion of their Single Farm Payment.

13.4 Code of Practice for the Agricultural Use of Sewage Sludge The Code was developed to complement the Regulations and its recommendations are based on scientific evidence and where relevant the requirements of the Regulations. The objectives of the code: ¾ No conflict with good agricultural practice ¾ Long term viability of agricultural activities is maintained ¾ Public nuisance and water pollution are avoided ¾ Human, animal or plant health is not put at risk The Code requires tighter limits than the Regulations, in particular: ¾ Tighter limits on soil concentration of zinc ¾ Tighter limits on soil concentration of cadmium

Sludge Code of Practice maximum permissible concentrations of PTEs in soil after application of sewage sludge and maximum annual rates of addition. Element Limit According to pH of soil Maximum permissible annual average rate of PTE addition over a 10 year period (kg/ha) 5.0<5.5 5.5<6.0 6.0- >7.0 7.0 Zinc 200 200 200 300 15 Copper 80 100 135 200 7.5 Nickel 50 60 75 110 3 For pH 5.0 and above Lead 300 n/a n/a n/a 0.15 Cadmium 3 n/a n/a n/a 15 Mercury 1 n/a n/a n/a 0.1 Chromium 400 n/a n/a n/a 15 Molybdenum 4 n/a n/a n/a 0.2 Selenium 3 n/a n/a n/a 0.15 Arsenic 50 n/a n/a n/a 0.7 Flouride 500 n/a n/a n/a 20

Long Term Sewage Sludge Experiments - Frequently Asked Questions

13.5 The “Safe Sludge Matrix” The “Safe Sludge Matrix” was an agreement developed between Water UK and the British Retail Consortium (BRC) in 1998 (www.adas.co.uk/matrix). The current Regulations are used alongside the voluntary “Safe Sludge Matrix”. All water companies signed up to the voluntary code via Water UK. The “Safe Sludge Matrix” introduced: ¾ A ban on untreated sludge use on agricultural land from the end of 1999. ¾ Strict controls on pathogen levels and the definition of Conventional and Enhanced final sludge treatment standards. ¾ Hazard Analysis and Critical Control Point (HACCP) controls on sludge treatment to achieve the above standards. ¾ Conventionally treated sludge can only be used on combinable and animal feeds crops and harvested forage crop. It can not be used on grazed grassland or on land used to grow ready to eat crops, fruit, horticultural crops etc.

“Safe Sludge Matrix” 3rd Edition

Crop Group Untreated Treated Enhanced treated sludges sludges sludges

Fruit xx  Salads xx  10 (30 month harvest month interval applies) harvest Vegetables x x  interval ⎬applies) (12 month harvest interval applies) Horticulture x x  Combinable & Animal x  Feed Crops 3 week 3 week - GRAZED x x no grazing  no grazing Grass (Deep injected or and and ploughed down only) harvest harvest & interval interval applies ⎬applies Forage - HARVESTED x ⎬

9 All applications must comply with the Sludge (Use in Agriculture) Regulations and Code of Practice x Applications not allowed (except where stated conditions apply)