Odour Management and Monitoring in Scottish Waste Water Treatment Plants

Background
Wastewater treatment works in Scotland have evolved substantially in the past 20 years. During the 1990s, major investments were made to comply with the Urban Wastewater Treatment directive. These investments were designed to protect the environment from the adverse effects of urban waste water discharges, and were not specifically focused on odour control. Odours continued to present issues at some sites, and in 2005, a statutory Code of Practice (CoP) for odour control at sewage works in Scotland was published by the Scottish Executive. Sewage works operators have been working under the CoP since the implementation of the Sewerage Nuisance (Code of Practice) (Scotland) Order in April 2006. At the same time, a number of sites have moved into private sector operation under the Private Finance Initiative (PFI). These changes have delivered ongoing improvements in odour performance. However, odours continue to be reported by local communities living close to some sites. Consequently, CREW has commissioned this project on behalf of Scottish Government, with the aim of reviewing and identifying good practice for odour management and monitoring at wastewater treatment plants in Scotland.

Research undertaken
The focus of the project was firstly to draw together and summarise existing statutory and non-statutory guidance on odour control relevant to sewage works in Scotland. Additional research was carried out to investigate the existence of potentially relevant odour monitoring and control methods, so that any new methods could be integrated into the analysis. Based on this, a “site odour potential framework” was developed to enable appropriate odour controls to be identified for an individual sewage works.

Detailed discussions were then held with facility operators and with local authority officers responsible for regulating odours associated with sewage treatment works in Scotland. Five specific sites were evaluated (Shieldhall, Ardoch, Dalmuir, Seafield and Levenmouth). The odour controls in operation at these works were evaluated against the controls that would be expected at these sites based on the odour potential framework. The odour performance of these sites gives an insight into the effectiveness of the controls applied. Based on this discussion and the supporting information, a streamlined guide to management of odours at sewage works in Scotland was development. This was designed to enable effective odour management techniques to be identified, taking into account the odour potential of individual sites.

An odour management and monitoring workshop consisting of representatives from Scottish water, regulators representing a number of local authorities, and operators was held. Feedback from the workshop has contributed to this report.