Situation and Compliance Report on the Disposal of Urban Wastewater and Sludge in Scotland 2020

3. Monitoring Compliance

Monitoring of public Wastewater Treatment Works (WwTW) is included in SEPA’s Annual Monitoring Plan (AMP) which is delivered by Scottish Water (or companies that operate public WwTW under Private Finance Initiative contracts) under Operator Self-Monitoring (OSM) in accordance with the Measurement Assurance and Certification Scotland (MACS) scheme. This is a quality assurance scheme designed to ensure that operator monitoring is fit for regulatory assessment. It includes minimum standards for data quality and links to sample frequency defined in the agreed AMP. Under this programme of work, influent and/or final effluent samples are taken and analysed to assess compliance with discharge quality limits set out in the licence.

Where non-compliance is identified, root cause analysis investigations are initiated to identify the reason(s) for non-compliance and the actions required to secure compliance. Actions required and the timescales for resolution depend on the scale and complexity of the work required. These will also identify where work is already planned or underway.

Scottish Water also completes regular site-specific scheduled tasks which include checks on discharge quality and any breaches of threshold limits (typically set at 70% of the licensed discharge quality limits). These are reviewed daily by the wastewater operational leadership team.

Another type of action to ensure compliance with licence conditions is the planned, and prioritised if necessary, emptying of sludge holding tanks so that bioresources are transferred to treatment centres in a timely manner, removing solids from the WwTW and reducing the risk of adversely affecting the discharge quality^[1].

During the initial Covid-19 pandemic lockdown, SEPA agreed that regulatory sampling should be suspended by wastewater operators from 27 March 2020 to 30 June 2020 in order to reduce Covid transmission risks for staff and the general population. The minimum number of samples required for UWWTR reporting were not, therefore, collected for most sites and it is not possible to assess compliance with annual average standards in 2020. Compliance for parameters assessed on a continuous basis has however been assessed using the normal lookup tables^[2] utilising the available samples taken out with the suspension period.

Following the suspension period, SEPA undertook a desk audit of licence compliance at a number of wastewater treatment works and confirmed that normal operational processes for managing treatment and any incidents had been followed during this time.

Compliance is assessed, as far as possible, based on available samples taken at public WwTW and SEPA data for private wastewater treatment sites in 2018. This data forms the basis of this report.

The data is provided in the form of an Excel spreadsheet as a supporting document accompanying this publication.