This project will investigate the the fate and the sources of a range of priority emerging contaminants to CECs Australian wastewater treatment plants (WWTPs), that will allow water and environmental authorities better diagnostic tool for proactively managing the release of emerging contaminants into treatment plants.

PhD Thesis underway by Madara Weerasooriyagedara.

The proposed project will evaluate new methods for synthesising novel fluorescent biopolymer nanoparticles (BNPs) in quantities that are suitable to facilitate challenge testing at full-scale and investigate techniques for stabilising the BPNs for distribution. The prepared BNPs will then be used to demonstrate a full-scale challenge test at a South East Water membrane treatment plant. The BNP test will be performed at the same time as a scheduled MS2 bacteriophage challenge test or pressure-based test in order to compare the two methods.

Wastewater must be treated to remove four classes of pollutants to levels that regulators consider safe for discharge to the environment: these are nutrients, micropollutants, total suspended solids and pathogens. Utilities are granted licenses to discharge based on the performance of their wastewater treatment plants (WWTPs) and legislation-derived guidelines which consider the social, economic, and environmental impacts of wastewater discharge. The problem is that there are substantial interpretative differences between States and jurisdictions. This research established a standard risk assessment framework that provides a transparent method for assessing the relative benefits of different disposal and treatment options, and which can be applied uniformly across Australia.

‘PFAS’ are a large class of chemical compounds, some of which can bioaccumulate or be toxic to humans and animals. Three PFAS: PFOS, PFOA and PFAS3; have been comprehensively investigated. An earlier study (WaterRA Project 2046) found PFAS in recycled wastewater and this raised concerns that crops irrigated with recycled water might lead to long-term chronic toxicity or bioaccumulation in soils. This research used existing datasets about PFOS, PFOA and PFAS3 to build a predictive conceptual model: the PFAS Exposure Model for Irrigation (PEMI). This was used to derive ‘Trigger Points for Investigation’(TPI); the levels of PFOS or PFOA or PFAS3 that, when measured in soil or recycled water, are high enough to cause concern and trigger investigation and action. Levels lower than the TPI’s are considered ‘safe’, and the PFAS3 TPI was higher than the median concentration measured in recycled wastewater from 17 Australian treatment plants (Project 2046). While these TPI are an excellent start to ongoing environmental and safety monitoring, the authors note that more data and research about plant uptake, animal transfer, degradation and leaching of additional PFASs will help validate and improve the PEMI.

Compliance with the Australian Guidelines for Water Recycling ensures that recycled wastewater does not present a health risk due to infectious pathogens or disease-causing chemicals. Many pathogens in wastewater are inactivated by disinfection treatments such as chlorination, but this causes a problem when disinfectants react with nitrogen compounds in wastewater and form Disinfection By-Products (DBPs), some of which pose a health risk. This research collected samples from four wastewater treatment plants (WWTPs) with different treatment methods and climate zones. A comprehensive and innovative analysis of the types of pathogens, various chemical forms of nitrogen and DBPs, and removal of these components during the recycling process, was related to season, climate and the four different treatment trains. It was concluded that the WWTP using a combined anaerobic/aerobic pond system was best at removing nitrogens and minimising DBP formation, but the best overall treatment performance was delivered by an activated sludge, oxidation ditch and infiltration pond WWTP in a temperate climate. Pathogens were found in influents but not treated effluents, and so were other nitrogen-removing micro-organisms. Treatment was better in summer, and the wastewater quality in these four WWTPs posed a low health and environmental risk to non-potable reuse.

Water treatment by micro- or ultrafiltration, or reverse osmosis is applied to a range of purposes, including recycling wastewater or reducing contamination sufficiently to make it safe for discharge to the environment. The problem is that membranes age, foul, are blocked by compounds in the feedwater and stop working. Ceramic membranes last longer and are more resistant to cleaning and defouling processes than other types of membranes. This research used a 25m2 ceramic microfiltration membrane pilot plant installed downstream of an ozone disinfection process to examine the effect of the integrated combination of these two units on turbid (3-5 NTU), highly fouling secondary effluent from a wastewater treatment plant. Adding coagulation with ‘PAC’ to the process stream more than doubled (flux) flows through the membrane. The pathogen indicators E. coli and MS2 were used to calculate Log Removal Values of >3.2 and 4 for protozoans and viruses respectively. It was concluded that the hybrid ozone-PAC – ceramic membrane treatment process was highly effective for treating and recycling challenging wastewaters.

Recycled stormwater has a range of possible uses that have different levels and types of human exposure. Before systems to collect and re-use stormwater are established it is important to identify and measure the risk stormwater poses to human health and the environment. This research collected samples from two sites after 12 rainfall events. Low levels of herbicides and other chemicals were found in all samples, lower than the threshold considered safe by the Australian Guidelines for Drinking Water (ADWG), but higher than levels Environment Protection Agencies permit for injection into natural acquifers. These low levels probably caused some of the toxic effects observed in the in vitro cell culture tests. There were very low levels of pathogens that can infect humans in some samples. It was concluded that stormwater should be treated before being re-used for a range of applications which might include replenishing acquifers and that it would be sensible to survey stormwater catchments and in some cases treat stormwater from specific contaminated sites because this would be more cost-effective than treating the entire stormwater outflow.

Water supply is usually continuous, and interruptions to supply are expensive and inconvenient. Most direct tests for the waterborne pathogens that cause illness are too slow and expensive to be used for the routine monitoring of water safety. Instead, the Hazard Analysis and Critical Control Point (HACCP) system, which was originally developed and implemented in the food industry, has been applied to manage microbiological and chemical contaminants in water treatment plants. This research extended the HACCP approach to water recycling and reclamation processes, by completing a literature review, collating and analysing existing datasets and case studies, conducting a gap analysis, running some pilot trials and preparing three HACCP template plans for use by water utilities, including those in America, when developing their own HACCP systems.