Environmental contextThe majority of biosolids produced in Australia from wastewater treatment processes are applied to agricultural land for beneficial use. We have demonstrated, through improvements to the analytical method, that levels of PFAS in biosolids are significantly higher than historically understood. The land application of biosolids could result in sensitive environments being exposed to PFAS at levels higher than previously anticipated. AbstractThe current industry standard for per- and polyfluoroalkyl substances (PFAS) analysis is for the measurement of only 28 PFAS, even though there are greater than 4700 PFAS known to be in existence. The total oxidisable precursor (TOP) assay, originally published by Houtz and Sedlak, is widely used as an estimate of the total perfluoro alkyl acids (PFAA) content of a sample, particularly in wastewater and biosolid matrices. The total PFAA content is an important measure of potential environmental contamination, which assists in the inference of potential harm that may occur from both well characterised PFAS, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), as well as lesser known precursor compounds and their breakdown products. With the majority of Australian biosolids beneficially applied to land, it is important to understand the future PFAS capacity before they are land applied to maintain the preservation of our agricultural and environmental assets. Our investigation of the TOP method and its application to biosolids involves a comparison of the Houtz and Sedlak method with a modified version coupled with a hydrogen peroxide pretreatment. The underperformance of the previously published method is demonstrated by its inability to sufficiently digest PFAS within biosolids. Therefore, the Houtz and Sedlak method significantly underestimated the levels of PFAS compared with the modified method, which showed a 10-fold increase in the measured PFAS after digestion. Further improvement of this modified method may provide a greater degree of accuracy for the TOP assay. The significant underestimation of the total PFAS load and, therefore, potential environmental harm has significant implications for public and agricultural health and compliance with regulatory limits.

A pilot study was carried out in a waste water treatment plant (WWTP) to recover phosphorous by Struvite precipitation from anaerobic digester centrate by means of Ostara's Pearl technology with the objective to assess technically and economically the performance and reliability of this process treating sidestreams with different concentrations of phosphorous and also to assess the quality of the fertilizer obtained. Different scenarios were studied: phosphorous inlet ranged from 31 to 150 mg PO 4 -P/L. The phosphorous removal varied from 60 to 81% depending on the influent, and the quality of the Struvite obtained was suitable to be used as a fertilizer. The economic assessment of implementing Struvite Pearl recovery process at full scale in WWTPs with anaerobic digestion (AD) and P-physicochemical or bio-P removal was carried out, taking into account investment (CAPEX) and operating costs (OPEX) of the Struvite recovery process and the economic savings due to phosphorous and ammonium removal in centrates. The results showed that with the current reagent strategies and investment costs, the Struvite recovery process was not economically feasible for WWTPs with AD and P-physicochemical removal. However, in the case of bio-P removal WWTPs with AD, the process can be an economic solution (pay back between 5 and 10 years, OPEX recovered due to the selling Struvite) which creates a high value re-cycled fertilizer and saves the environment due to the higher efficiency of the fertilizer usage.