Using indicators to assess microbial treatment and disinfection efficacy

One of the primary goals of this chapter is to provide the reader with a broad understanding and appreciation of the various roles indicators play in the design, risk assessment and performance monitoring of commonly used wastewater treatment and disinfection processes. The chapter outlines how different indicators such as faecal bacteria, bacteriophages, bacterial spores, parasites and helminth eggs can be used to assess the efficacy of microbial treatment and disinfection in a range of natural and engineered systems. The usefulness of the various indicators will be explored by assessing their presence and behaviour in raw sewage, primary, secondary, tertiary treated, final effluent, sludge and in reclaimed wastewater used for different reuse applications, such as irrigation of crops.
Using the very latest international scientific research, indicator performance, reliability, ease of use, safety, cost, and suitability for use in resource-limited and/or emergency settings will be assessed. Therefore, the content should provide a state-of-the-art reference resource to help guide water managers, regulators, stakeholders and anyone interested in gaining a better understanding of the advantages and limitations of current treatment indicators.

The chapter will summarize the extensive range of methods, from the enumeration and detection of traditional faecal indicators, such as Escherichia coli, Enterococcus, alternative indicators like spores of Clostridium perfringens and coliphages, to the application of novel surface modified “micro mimics” used for elucidating pathogen attenuation and transport in natural and engineered treatment systems. Readers should also gain an insight into the fate, behaviour and transport of various indicators and the different ways they may be applied in natural and engineered systems e.g. as surrogates for pathogens, as regulatory parameters, and as treatment performance parameters. As such, the content should help water managers, engineers, and water and sanitation specialists to decide on the most appropriate parameter, or group of parameters to use during microbial treatment and disinfection efficacy investigations.
Reference to international case studies by leading experts in the field should help the reader gain a broader insight into the potential application and geographical stability of the most promising indicators of treatment and disinfection efficacy. As such, it offers an international perspective on both current research and provides guidance on the potential utility and future use of the various microbial monitoring tools identified. The chapter will also be furnished with examples on the microbial reductions achieved using both intrinsic indicators as well as ‘spiked’ indicators in both large-scale and small-scale natural and engineered treatment systems, found in different parts of the world.

The effectiveness and suitability of microbial indicators and traditional surrogates for predicting pathogen fate and transport, will also be investigated with respect to high and low-income urban, peri-urban and rural settings, in order to identify the most useful (repeatable, reproducible) approaches and where possible highlight ‘best practise’. The chapter concludes with a summary of the current state-of–the-art, before identifying existing knowledge gaps and future challenges facing practitioners tasked with the further development and application of indicators of treatment efficacy.