Report No FR/D0007

Final Report


Sept 1992


This report reviews the current applicability of four processes used for disinfection of sewage, microfiltration, ultraviolet radiation (UV), ozonation and lime treatment, and examines the available data on these processes in respect of efficacy of micro-organism inactivation, environmental effects and capital and operating costs.

On micro-organism removal microfiltration can be very effective even if used for low quality effluents. However, the reliable application of this technology at full scale to low quality effluent is yet to be fully demonstrated, and considerable development work is currently being undertaken. UV also appears to be effective in reducing numbers of indicator organisms, pathogenic bacteria and viruses. Its application is limited to good quality effluents, ie, essentially secondary effluents. However reactivation of bacteria may occur in some cases following UV disinfection.

Only limited useful data are available to assess the application of ozone despite its widespread use in the USA. Ozone appears to moderately inactivate pathogenic bacteria and viruses in secondary effluents.

Clariflow acts as a primary treatment process as well as achieving a high degree of disinfection at high pH. The process seems to be effective in removing pathogenic bacteria, spores and cysts from raw sewage. Data for viral inactivation are scarce, with different reports stating reasonable or poor removal.

The report examines practical aspects of disinfection systems and environmental effects, although available information on environmental effects is somewhat limited. Costs are also examined.

The report concludes with a review of novel treatment processes and further research needs.

Copies of the report are available from FWR, price 15.00, less 20% to FWR Members.