Traditionally, Membrane Bioreactor (MBR) Validation is focussed on performance during commissioning when membranes are new, and the range of operating conditions are limited. As membranes age it is important to understand how MBR performance changes to have confidence in the quality of the water produced. Gathering data on the relationships between operational monitoring parameters such as turbidity and pathogen removal during the life of membranes would assist operators to understand the ongoing performance of membranes compared with initial performance.

The former Water Recycling Centre of Excellence developed the MBR Validation Protocol. This protocol was prepared as part of NatVal to provide guidance for the validation of MBRs. It proposed a tiered approach that allowed for a simplified process where log reduction values (LRVs) are claimed.

The aim of this project is to collect and review performance data from a broad range of operating MBR facilities in Australia to understand the pathogen LRV performance in relation to operating conditions and monitoring parameters; targeting a range of membrane age, integrity, performance, and control. This will allow water managers to understand and predict the ongoing performance of MBR plants compared to initial performance, informing future MBR design and also assisting in optimising membrane lifecycle planning. This research will also provide operators and regulators with greater confidence MBR operation throughout the asset life, and lower the whole of life cost of MBR ownership for water service providers by maximising the validated operating envelope.

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.

Stormwater and treated wastewater can contain infectious pathogens. The Australian Guidelines for Water Recycling (AGWR) require that these are removed during recycling, and that recycling processes pass “Quantitative Microbial Risk Assessments” (QMRA). The problem is that these QMRA’s are often based on estimates. This research further developed methods (begun in WaterRA project 3002) to generate real-world measurements and data relevant to firefighters and domestic users because there are concerns that small amounts of recycled non-potable water might be inadvertently ingested. To test this, a harmless chemical, cyanuric acid, was added to safe water, then twenty-six volunteers used it, and a domestic high-pressure sprayer, to clean a full-sized model car for 10 minutes. The volunteers then collected their own urine for the next 24h because if this test-water is ingested, the cyanuric acid can be measured in the urine. From this it was discovered that the volunteers ‘drank’ an average of 0.13mL. This led to the conclusion that the conservative estimates in the AGWR currently protect domestic non-potable recycled water users, but that prolonged and/or high intensity occupational use of high-pressure sprays should be investigated further.

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.

In an earlier project stormwater was collected from an urban environment, treated through electrolysis, injected into and retrieved from an aquifer, and reused for greywater irrigation. This research used the previously established hardware and software for ten months to gather data about operational efficacy, reliability and costs. E. coli, a common indicator of faecal contamination, was barely removed by electrolysis, and other pathogens were not examined, which prevents assessment of water quality or its compliance with the AGWR. 20878 kL stormwater were treated and added to the aquifer, and 5886 kL retrieved for irrigation. Total operational costs were $29344 and the cost of processed water ranged from $0.13 to $0.28 per kL. The purpose-designed software and computerised telemetry was reliable and suitable for upgrading with security features. It was concluded that the system has potential for further development as an alternative to using mains potable water to irrigate open public spaces.

Cryptosporidium is a waterborne microscopic parasite with different forms at various stages of its lifecycle. One form, the spherical oocyst, is excreted by infected people and transported in rivers and surface waters. In the first part of this research (WaterRA Project 2015) an in vitro cell culture ‘infectivity assay’ test was developed to be able to differentiate between live infectious and dead ‘safe’ oocysts. In the second part of this research the ‘infectivity assay’ was used to examine the frequency and occurrence of infectious cryptosporidia at different stages of wastewater treatment. Samples from five wastewater treatment plants were examined. It was concluded that there is a strong seasonal element to infectious oocyst removal in which winter rainfall and temperatures reduced removal efficacy but that exposure to sunlight is an effective way to inactivate infectious oocysts and make recycled water safe and fit for purpose.

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.

Membranes are used to remove viruses from treated wastewater to make it safe for discharge or recycling. It is important to monitor the integrity of membranes and check that viruses cannot break through. This creates a need for surrogates that are cheaper, safer and easier to use than the non-hazardous indicator virus currently applied to test membrane integrity. This research synthesised a series of fluorescent nanoparticles with similar dimensions to viruses, with the idea that the fluorescence would support continuous in situ monitoring in real time, but unfortunately the nanoparticles did not emit enough fluorescence and could not be detected in the product water.

Smaller and regional Wastewater Treatment Plants (WWTPs) have the capacity to recycle wastewater for agricultural use, but the cost of obtaining regulatory approval or ‘accreditation’ is prohibitive. One reason for this is that each WWTP must demonstrate that its processes and operations consistently remove pathogens that cause infectious diseases in humans. Operating conditions include flow rate through the WWTP, and temperature in the activated sludge component of the WWTPs. Although pathogen ‘log removal values (LVR)’ were obtained for a WWTP at 19-20°C in Part I of this project (WQRA project 2001), these values cannot also be attributed to summer temperatures of 26°C. This research determined LRVs for ‘new’ WWTP operating conditions and combined the data with data from Phase I (Project 2001) for analysis. One of the conclusions from Part II was that faster flow rates associated with increased rainfall reduced pathogen LRVs.

Some wastewater treatment plants (WWTPs) use membrane bioreactors (MBR). These contain a microporous membrane which clarifies treated wastewater by removing microbial organisms. Wastewater must also be treated to remove nitrogen and phosphorus, which can act like uncontrolled fertilisers if they are released to the environment. Iron or aluminium salts added to the wastewater react with phosphorus and make solid particles which can be ‘caught’ and separated in the MBR. The problem is that the amounts of iron salts commonly added to some WWTPs foul the membrane and reduce its performance. This research used a laboratory-scale MBR to discover that lower amounts of specific iron salts effectively reduce phosphorus to levels that are safe to discharge while also reducing fouling and increasing the operating life of the membrane. Another conclusion was that ascorbic acid (vitamin C) cleaned iron-associated foulants from membranes more effectively than the conventional cleaning agent, citric acid.