Use of micropollutant indicator ratios to characterize wastewater treatment plant efficiency and to identify wastewater impact on groundwater.

Contamination by wastewater has been traditionally assessed by measuring faecal coliforms, such as E. coli and entereococci. However, using micropollutants to track wastewater input is gaining interest. In this study, we identified nine micropollutant indicators that could be used to characterize water quality and wastewater treatment efficiency in pond-based wastewater treatment plants (WWTPs) of varying configuration. Of 232 micropollutants tested, nine micropollutants were detected in treated wastewater at concentrations and frequencies suitable to be considered as indicators for treated wastewater. The nine indicators were then classified as stable (carbamazepine, sucralose, benzotriazole, 4+5-methylbenzotriazole), labile (atorvastatin, naproxen, galaxolide) or intermediate/uncertain (gemfibrozil, tris(chloropropyl)phosphate isomers) based on observed removals in the pond-based WWTPs and correlations between micropollutant and dissolved organic carbon removal. The utility of the selected indicators was evaluated by assessing the wastewater quality in different stages of wastewater treatment in three pond-based WWTPs, as well as selected groundwater bores near one WWTP, where treated wastewater was used to irrigate a nearby golf course. Ratios of labile to stable indicators provided insight into the treatment efficiency of different facultative and maturation ponds and highlighted the seasonal variability in treatment efficiency for some pond-based WWTPs. Additionally, indicator ratios of labile to stable indicators identified potential unintended release of untreated wastewater to groundwater, even with the presence of micropollutants in other groundwater bores related to approved reuse of treated wastewater.

Removal of organic micropollutants in waste stabilisation ponds: A review.

As climate change and water scarcity continue to be of concern, reuse of treated wastewater is an important water management strategy in many parts of the world, particularly in developing countries and remote communities. Many countries, especially in remote regional areas, use waste stabilisation ponds (WSPs) to treat domestic wastewater for a variety of end uses, including using the treated wastewater for irrigation of public spaces (e.g. parks and ovals) or for crop irrigation. Thus, it is vital that the resulting effluent meets the required quality for beneficial reuse. In this paper, both the performance of WSPs in the removal of organic micropollutants, and the mechanisms of removal, are reviewed. The performance of WSPs in the removal of organic micropollutants was found to be highly variable and influenced by many factors, such as the type and configuration of the ponds, the operational parameters of the treatment plant, the wastewater quality, environmental factors (e.g. sunlight, temperature, redox conditions and pH) and the characteristics of the pollutant. The removal of organic micropollutants from WSPs has been attributed to biodegradation, photodegradation and sorption processes, the majority of which occur in the initial treatment stages (e.g. in the anaerobic or facultative ponds). Out of the many hundreds of organic micropollutants identified in wastewater, only a limited number (40) have been studied in WSPs, with the majority of these pollutants being pharmaceuticals, personal care products and endocrine disrupting compounds. Thus, future research on the fate of organic micropollutants in WSPs should encompass a broader range of micropollutants and include emerging organic pollutants, such as illicit drugs and perfluorinated compounds. Further research is also needed on the formation and toxicity of transformation products from organic micropollutants in WSPs, since the transformation products of some organic micropollutants can be more toxic than the parent compound. Combining other wastewater treatment processes with WSPs for removal of recalcitrant organic micropollutants should also be considered.

Use of Alum for Odor Reduction in Sludge and Biosolids from Different Wastewater Treatment Processes.

Applicability of alum addition to wastewater sludge and biosolids produced from different treatment processes was evaluated as a means of odor reduction. Four water resource recovery facilities (WRRFs) were chosen for this study: two used mesophilic anaerobic digestion and two used oxidation ditch processes. The experiments were conducted on a laboratory scale and in all cases the alum was added prior to dewatering. This is the first report of the application of alum for odor reduction in oxidation ditch processes. Alum addition was effective in reducing odors in anaerobically digested biosolids. Addition of 4% alum to anaerobically digested liquid biosolids prior to dewatering resulted in a 60% reduction in the peak odor concentration in the laboratory dewatered cake, relative to the control sample. Alum addition did not reduce odors in dewatered sludge from oxidation ditch processes.

Odour reduction strategies for biosolids produced from a Western Australian wastewater treatment plant: results from Phase I laboratory trials.

This study investigated sources of odours from biosolids produced from a Western Australian wastewater treatment plant and examined possible strategies for odour reduction, specifically chemical additions and reduction of centrifuge speed on a laboratory scale. To identify the odorous compounds and assess the effectiveness of the odour reduction measures trialled in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS SPME-GC-MS) methods were developed. The target odour compounds included volatile sulphur compounds (e.g. dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide) and other volatile organic compounds (e.g. toluene, ethylbenzene, styrene, p-cresol, indole and skatole). In our laboratory trials, aluminium sulphate added to anaerobically digested sludge prior to dewatering offered the best odour reduction strategy amongst the options that were investigated, resulting in approximately 40% reduction in the maximum concentration of the total volatile organic sulphur compounds, relative to control.