Report No SR3578/1

DISPOSAL OF SEPTIC TANK EFFLUENTS IN
AREAS WITH A SHALLOW WATER TABLE

SR3578/1

Oct 1994

SUMMARY

Large numbers of properties in isolated rural areas of Scotland and Northern Ireland are reliant on septic tanks for treatment of their sewage. However there are no universally accepted guidelines to deal with the safe disposal of the effluent from these treatment systems in areas where there may be a risk of groundwater contamination, for example in locations with shallow water tables where groundwater is used for potable supplies. The development of such guidelines would be of great benefit to the regulatory water authorities in Scotland and Northern Ireland particularly with respect to the evaluation of planning applications which propose the disposal of septic tank effluents to groundwater.

Consequently, in 1993 WRc was awarded a contract by the Scotland and Northern Ireland Forum for Environmental Research (SNIFFER) to carry out research into the effects of the disposal of septic tank effluents in areas with shallow water tables. The objectives of the research programme were:

  1. to identify and evaluate any existing guidelines currently used overseas;
  2. to review research carried out to date into the problems of effluent disposal from septic tanks and to relate that research to the specific problems of Scotland and Northern Ireland;
  3. to carry out site investigation work to validate the findings of the literature study;
  4. to develop practical and workable guidelines for use by regulatory officers in Scotland and Northern Ireland.

The research programme comprised two principal areas: a comprehensive literature study and groundwater quality surveys at a site in Scotland, including the use of bacteriophage tracers. The results of these two areas of study were then used to develop g uidelines which are reported here.

KEY WORDS

Septic tanks, effluent disposal, groundwater, bacteriophage

Copies of the report are available from FWR, price 12.50, less 20% to FWR Members.