Development of new benchmarking systems for wastewater treatment facilities
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2017-06-30Author
Doherty, Edelle
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Abstract
In the European Union, the Urban Waste Water Treatment Directive (UWWTD) of 1991 sets out the requirements for the collection, treatment and discharge of wastewater, to protect the environment from the adverse effects of the discharge of untreated wastewater. Compliance rates with the UWWTD are quite varied within member states, particularly in sensitive areas where regulation is more stringent. Additionally, wastewater treatment can be an energy intensive process. With rising energy costs and growing concerns regarding greenhouse gasses, environmental sustainability is becoming a key aspect of wastewater treatment. The Water Framework Directive (WFD), which focuses on water resource quality across the European Union (EU), is a big driver for achieving effective management of wastewater treatment plants (WWTPs).
Wastewater treatment plants typically operate continually and are subject to several pressures (e.g. population changes, varying influent due to storm water, more stringent environmental regulation etc.), making the implementation of resource efficiencies uniquely challenging. These challenges mean that, without intervention, WWTPs will become more resource intensive as they strive to meet environmental regulations. Ensuring regulatory compliance while operating in an environmentally sustainable manner, amongst other responsibilities, can result in WWTP management becoming a complex process. Performance assessment and benchmarking has developed as a key aspect of WWTP management. However, benchmarking has not been systematically applied in the Irish wastewater sector to date. Benchmarking is a data-driven process, and can only be successful if careful consideration is given to data availability and accuracy. In Ireland, data availability is a major concern. The only data readily available and accurate is that which is supplied for regulatory purposes. Without sufficient data, assessing the accuracy of the available data and identifying comparable WWTPs becomes increasingly complex.
Improved data management practices can be achieved through WWTP benchmarking; WWTPs in countries which have employed benchmarking for several years have experienced increased data availability. To overcome the challenge of data availability during the early years of a benchmarking project, it is necessary to identify interim methods, which are applicable in the current state of Irish WWTPs, to reduce the negative effects of data availability and data accuracy on benchmarking. Facilitating the successful benchmarking of Irish WWTPs in the present-day and at a national level (using these interim and easily-applied methods) can (i) improve WWTP management practices, (ii) accelerate the improvement of data collection practices and (iii) lead the way to the inclusion of more advanced benchmarking applications in the years to come, when data availability and accuracy issues are corrected.
This study aimed to address the challenges associated with benchmarking in a low data availability environment by developing and piloting a WWTP benchmarking methodology and toolkit which was cognisant of data availability and data accuracy issues. The developed performance assessment methodology was piloted in several WWTPs of varying characteristics over an extended period. Additionally, the developed toolkit was supplied to key stakeholders for user testing. The results from piloting and stakeholder testing informed several methodology and toolkit upgrades to enhance usability, key performance indicator (KPI) calculation, result reporting methods and applicability to WWTPs of various configurations. Many of these upgrades were recommended by key stakeholders with a view to integration of the methodology into WWTP management at a national utility level in Ireland.
A decision support tool was developed to work in conjunction with the benchmarking methodology to identify WWTPs which are comparable for benchmarking purposes based on regulatory compliance data. The decision support tool was applied to Ireland’s operational and licenced WWTPs and facilitated the rapid identification of comparable WWTPs. The tool is adaptable to other groups of WWTPs and provides a means of repeating the analysis with ease, when compared against any manual method of identification.
An additional study was conducted to assess the statistical agreement between various sampling methods to assess the feasibility of utilising more cost-effective grab sampling methods in the place of flow-paced sampling methods for WWTP performance benchmarking purposes. This study shows that using more cost-effective and low maintenance methods may be feasible in a WWTP. However, this may need assessment on a case-by-case basis.
Collectively, the methods and studies presented in this research offer a means of benchmarking in a low data availability environment, whilst improving data collection and management practices both by (i) assessing data accuracy issues without the need for high levels of data availability, (ii) identifying comparable WWTPs based on data reported for regulatory purposes and (iii) presenting a method of assessing the feasibility of adopting low-maintenance wastewater sampling methods in a WWTP.