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Toxic prescribed chemicals in Sewage Effluent Discharged in the UK

AFM filtration can be applied to the filtration of waste water in order to eliminate, or at least greatly reduce the level of prescribed substances discharge into rivers and the marine environment.  We have shown that AFM can be used in combination with diffused aeration activated sludge waste water treatment of landfill leachate water to essentially prevent the discharge of toxic prescribed chemicals.  By way of example Table 1 below presents typical data for TBT ( tri-butyltin).

Table 1 shows that the AFM filter was removing TBT to below the limit of detection in all but one of the analyses. The results  demonstrate that the AFM filter is concentrating the TBT in the back-flush water and there by preventing it from being discharged to the environment.  Indeed the levels discharge by the landfill site can be up to 400 times lower than a level discharge by a sewage works located up-stream of a drinking water abstraction point.

Table 2  Environment Agency maximum permissible sewage effluent discharge levels in the UK

Considering that the quantities of water discharge by sewage works relates to approximately 160 litres per person per day, allowing prescribed substances at the above concentration to be discharged represent a very large quantity of chemicals.  These chemicals such as TBT are bioaccumulated in the marine environment. The chemicals do not disappear but continue accumulate around the food chain increasing in concentration all of the time. The UK government guidelines now suggest that you should not eat more that two oily fish per week.  However fish meal is also used to feed cattle, chickens and other animals,  so we can not escape the problem.

We know that the population are now exposed to much high levels of chemicals than at any stage in the past.  We also know that the level of cancers in the UK have increased by around 30% over the last 30 years.  Unless some action is taken to reduce the use of chemicals and their discharge into the environment the situation can only deteriorate.

Dryden Aqua under European Commission Research project have confirmed that simple AFM tertiary treatment of sewage effluent is a cost effective means of treating waste water.  Indeed for new sewage works the adoption of AFM as opposed to humus tank sedimentation may indeed result in a lower construction costs than existing systems. The life cycle costing have also proved to be a great deal lower than any existing technology.  However the main aspect is that AFM represent effective tertiary treatment of sewage effluent, compliance with very tight discharge consents and virtual elimination of prescribed chemicals.

List 1 Prescribed substances

The Dangerous Substances Directive 76/464/EEC listed 129 so-called "black list" list 1 substances which were considered to be so toxic, persistent or bio-accumulative that efforts to control chemical releases and prevent pollution should be given the highest priority.

From the original list of 129 substances, Daughter Directives have been adopted providing emission limits and quality objectives for receiving water. The implementation of best available technology (BAT) is required under PPC (pollution prevention and control) authorisation for the elimination of red list  List 2 substances in discharges to water.

The black list substances covered by Daughter Directives for elevation to red list status are contained in the Environmental Protection (Prescribed Processes and Substances) Regulations 1991 (as amended). They are as follows:-