An investigation into the effects on soil quality and fertility of the heavy metals present in sewage sludge has published interim findings today.

The results will help inform the sustainable recycling of organic material to land to improve soil quality. Spreading treated sewage sludge on agricultural land provides organic matter and nutrients and maintains soil carbon, as well as offering what is in many circumstances the best environmental option for recycling of sewage sludge. The alternative disposal routes are landfill or incineration, both of which waste a potentially valuable resource.

Headline results show that under certain conditions metal-rich sludge could impact upon some microbial groups, with implications for soil quality over the long term. However, the  results represent the potential impacts under a worst-case scenario. Moreover,  the long timescale over which the effects were projected means that there is good time, before there is any significant risk of damage occurring, to properly investigate the issues arising from the experiments so far.

Further work is now planned to understand the mechanisms behind the identified impacts and how these could be influenced.