Wastewater Biosolids Treatment and Use

Introduction

The Chartered Institution of Water and Environmental Management (CIWEM) is an independent professional body representing over 12,000 environmental professionals. CIWEM's agreed purpose is to develop and promote better and integrated management of the environment; to foster a deeper understanding of water and environmental issues and to enhance the quality of people's lives. This is achieved through CIWEM's Royal Charter, education, training and professional development; dissemination of information; conferences and events; research and publications; contact with Government agencies and other bodies, partnerships with other organisations and the publication of Policy Position Statements (PPS).

This PPS is a revision of PPS1, published in November 1998.

Purpose

1. To outline the main issues relating to wastewater biosolids treatment and use, taking account of legislation, water industry operations and other matters of concern to legislators, regulators, the public and other stakeholders, particularly in a UK context.

Background

1. The collection and treatment of municipal wastewater is one of the most significant contributions to improved public health. Biosolids are the solids separated from wastewater and created during its treatment.

2. The use of biosolids on land completes nutrient cycles and conserves organic matter. It feeds the soil and promotes better structure and life within the soil. It is thus a component of sustainable development.

3. In December 1998, an agreement was reached between Water UK and the British Retail Consortium, which developed additional guidelines for the use of biosolids in agriculture. The agreement has been adopted across the UK, and its major points will be incorporated into amendments to the "Sludge Regulations" which are currently being revised.

4. The inputs of potential pollutants at point sources (i.e. factories) have been effectively controlled over the last 20 years so that their concentrations in biosolids have been dramatically reduced. For most works further reductions are now limited by contributions from diffuse sources such as dental amalgam (mercury), cosmetics (zinc), plumbing (copper).

5. The risk to health (i.e. the risk of pathogen transmission) is controlled by biosolids treatment and/or restrictions on how land is used after biosolids have been applied and intervals to harvesting, grazing, etc.

6. The risk of adverse environmental impact when biosolids are used on agricultural land is controlled through the soil limit values set in the Sludge Regulations. These limit values are based on sound science and are reviewed on the basis of continuing R&D.

7. Biosolids treatment and their use or disposal account for approaching half of the total cost of wastewater treatment.

8. Biosolids contain organic matter and plant nutrients separated from wastewater, and concentrated during its treatment.

9. Wastewater biosolids treatment / use in the EU takes place within the framework of the relevant directives (CEC 1986 and CEC 1991), implemented as national regulations, which may in turn be complemented and amplified by codes of practice. The EU Commission is in the preliminary stages of revising the Directive with the objective of promoting beneficial use.

10. The use of biosolids on land is, in many cases, the Best Practicable Environmental Option (BPEO).

11. When biosolids are used on land, they substitute for part of the mineral fertiliser needs of crops, and because of the gradual release nature of the nutrients the crops are frequently healthier and therefore need fewer applications of crop protection chemicals.

Key issues

1. CIWEM considers that term "sewage sludge" is really a misnomer because up to 40% of the solids are excess biomass that has grown during the wastewater treatment process and that was not originally present in the sewage. CIWEM considers it should be replaced with the terms "wastewater biosolids" or "biosolids".

2. Although the use of biosolids in agriculture is regulated, there is no EU framework for the use of biosolids in forestry or for land restoration. An even more serious deficiency is with regard to the spreading of manures and other residuals on land. They can have similar environmental effects to biosolids, but they are 20 times greater in quantity than biosolids. CIWEM considers that it is inconsistent to regulate 5% and not the remaining 95% and welcomes the start that the Commission has made in reducing this inconsistency by increasing the range of residuals that it is considering.

3. CIWEM applauds the work of water utilities in the UK (Water Companies in England and Wales, Water Authorities in Scotland and the Water Service in Northern Ireland), to complete all capital works and commissioning operations to comply with legislation.

4. There is no documentary evidence that there have been adverse effects on public health where biosolids treatment and use have conformed to existing legislation. However the world is changing. The number of reported food poisoning incidents has risen unacceptably; bacteria with high infectivity and/or antibiotic resistance are emerging. In the light of this there is a case for a more precautionary approach for all materials that are applied to land, however CIWEM considers that the application of precaution should be proportionate to risk.

5. Nuisance may occur if the operation of wastewater treatment works or biosolids recycling sites cause offensive odours or disruptive vehicle movements. However, implementation of good practice can bring about substantial amelioration and often elimination of such problems.

6. The recommendation of the House of Commons Select Committee (February 1998) that all biosolids used on agricultural land should be 'stabilised and pasteurised' would require significant extra investment by the water utility companies. However in the light of factors discussed above, and the importance of ensuring public and stakeholder confidence, CIWEM considers extra attention to pathogen reduction may be desirable even if the need has not been strictly proved.

7. CIWEM considers that the term "disinfected" is preferable to "pasteurised". The latter implies very restricted process conditions whereas disinfection describes processes that safeguard health.

8. In CIWEM's view it is essential that the use of biosolids on land remains an option for the recovery of biosolids. Other routes, notably incineration and other methods of thermal destruction, are generally much more expensive, and landfill capacity should not be wasted on materials that can be beneficially used.

9. CIWEM considers that the known risks from controlled use of biosolids on land are very small, however CIWEM considers that if there are risks they should be borne by the producer of the biosolids and not by the landowner. CIWEM considers that those who supply biosolids (or other organic soil treatments) for use on land should indemnify landowners for an extended period (perhaps 20 years) against the possibility of adverse effects from the biosolids until the risk of such effects emerging could be considered nil.

10. CIWEM commends the British Retail Consortium (as lead body for the UK food industry) and Water UK (representing the water utilities in UK) for negotiating agreement on the use of biosolids in agriculture. CIWEM considers this a world milestone. It commends the commitment to continuous improvement in operation and to subjecting its operations to independent audit. CIWEM recommends biosolids recyclers to continue to take proactive measures to build and ensure stakeholder acceptance and confidence.

Conclusions

1. Generally wastewater biosolids treatment and use are being performed efficiently in the United Kingdom. However, to ensure environmental, animal and human health are protected, to guarantee the continued availability of agricultural land for the beneficial use of biosolids and other residuals, and to meet current and future stakeholder concerns, there should be a consistent framework of controls for all residuals applied to land.

2. Whatever the Government, stakeholders or public opinion demand, the next five years will present the water utilities with a challenge to develop more advanced, environmentally friendly and cost effective operational practices.

References

CEC (1986) Council of the European Communities On the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture (86/278/EEC) Official Journal of the European Communities No L 20/43-48 CEC (1991) Council of the European Communities Concerning urban wastewater treatment (91/271/EEC) Official Journal of the European Communities No L 135/40-52

January 2001

Note:- CIWEM Policy Position Statements (PPS) represents the Institution's views on issues at a particular point in time. It is accepted that situations change as research provides new evidence. It should be understood, therefore, that CIWEM PPS's are under constant review, that previously held views may alter and lead to revised PPS's