Action Synopsis: Bat Conservation About Actions

Change effluent treatments of domestic and urban waste water

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects of different sewage treatments on the activity of foraging bats. The study was in the UK. We found no studies that evaluated the effects of changing effluent treatments of domestic and urban waste water discharged into rivers on bat populations.



  • Abundance (1 study): One replicated, site comparison study in the UK found higher activity (relative abundance) of foraging bats over filter bed sewage treatment works than over active sludge systems.


About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, site comparison study in 2003 at 30 sewage treatment works and in central and southern Scotland, UK (Park & Cristinacce 2006) found that percolating filter beds had higher activity of Pipistrellus spp. over them than activated sludge systems, and activity over filter beds was similar to that along nearby river banks. The number of Pipistrellus spp. bat passes recorded over percolating filter beds (54) was higher than over activated sludge systems (9). Activity of Pipistrellus spp. over filter beds (average 15 bat passes/site) was also similar to that along nearby river banks (23 bat passes/site), whereas activity over activated sludge sites (3 bat passes/site) was lower than along nearby river banks (18 bat passes/site). At filter beds, waste water is sprayed over inert filter material creating a microbial film which supports high insect numbers. In activated sludge systems, sewage and bacterial sludge are mixed creating an unfavourable habitat for insects. At each of 30 sites (18 filter bed, 12 activated sludge), bat activity was recorded with bat detectors at three points/site for 15 minutes each after dusk in June–August 2003. At each of 23 sites (15 filter bed, 8 activated sludge), recordings were also made at two points on the river bank 50 and 75 m upstream from the sewage treatment works.

    Study and other actions tested
Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.


Where has this evidence come from?

List of journals searched by synopsis

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Bat Conservation

This Action forms part of the Action Synopsis:

Bat Conservation
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