Report No FR0216

Sept 1991

The objective of this interim report is to review and technically evaluate the various processes for nutrient removal. Processes may be either chemical or biological but must achieve particular effluent standards for a range of sewage treatment works sizes.

The EC Urban Wastewater Treatment Directive states that there will be the need to achieve total nitrogen and phosphorus emission standards of 10 and 1mg/1 respectively for "sensitive areas". It is proposed that these be implemented by 1998 and therefore there is a need for the UK Industry to define what are the most appropriate technical and economic process solutions.

A review and evaluation of processes for nutrient removal has been performed and has shown that great progress has been made in the past ten years with nutrient removal systems and in particular with respect to biological phosphorus removal systems. It seems likely that Biological phosphorus removal processes will need to be followed by a chemical dosing and settlement stage (using a low chemical dose) to ensure compliance with less than 2mg P/l. However, more information is required and should be obtained from:-

1. UK chemical phosphorus removal plants.
2. Scandinavian and European chemical addition and biological phosphorus removal plants.
3. American biological nitrogen and phosphorus activated sludge plants.
4. Biological nitrogen removal attached-growth processes, and costs for the carbon source. This information will be used in the selection strategy for processes to meet different requirements, available Q4 91, and in the final report which will detail a comparative review of all technical and cost information, for completion Q1 92. The final report will include any further references unearthed in talking and corresponding with plant operators.

More data is required and should be obtained particularly from operational:

1. Nitrogen removal processes.
2. Phosphorus and nitrogen removal activated sludge plant to ascertain the consistency of performance, and the effects of a range of influent wastewater parameters.

The literature review covers the existing and proposed legislation covering nutrients from point and non-point sources. The mechanisms of nutrient removal both chemical and biological are described and then nutrient removal processes are described with some actual performance data.

The performance of all processes to meet the proposed legislation is discussed and a conclusion given.

Copies of the report are available from FWR, price £35.00, less 20% to FWR Members.