Verification of an alternative sludge treatment process for pathogen reduction at two wastewater treatment plants in Victoria, Australia

Abstract

At South East Water wastewater treatment plants (WwTPs) in Victoria, Australia, biosolids are stockpiled for three years in compliance with the State guidelines to achieve the highest pathogen reduction grade (T1), suitable for unrestricted use in agriculture and landscaping. However, extended stockpiling is costly, may increase odour nuisance and greenhouse gas emissions, and reduces the fertiliser value of the biosolids. A verification programme of sampling and analysis for enteric pathogens was conducted at two WwTPs where sludge is treated by aerobic and anaerobic digestion, air drying (in drying pans or solar drying sheds) and stockpiling, to enumerate and, if present, monitor the decay of a range of enteric pathogens and parasites. The sludge treatment processes at both WwTPs achieved T1 grade biosolids with respect to prescribed pathogenic bacterial numbers (<1 Salmonella spp. 50 g−1 dry solids (DS) and <100 Escherichia coli g−1 DS) and >3 log10 enteric virus reduction after a storage period of one year. No Ascaris eggs were detected in the influent to the WwTPs, confirming previous studies that the presence of helminth infections in Victoria is extremely low and that Ascaris is not applicable as a control criterion for the microbiological quality of biosolids in the region.

Physicochemical Properties of Biochars Produced from Biosolids in Victoria, Australia

“…In brief, 1:5 ( w / v ) sample/Milli-Q water suspensions were prepared and shaken for 1 h on a mechanical shaker and the EC was recorded on the clear supernatant solution after approximately 30 min. The pH of the supernatant solution was measured according to Method 4B2 [ 17 ].…”

“…Total K, total P, total Ca, total Mg, and heavy metals in biosolids and biochars were analysed according to Method 17A1 [ 17 ]. Samples were oven-dried at 105 °C prior to analyses.…”

“…However, South East Water obtained approval from EPA Victoria in December 2015 to use 1- and 2-year-old biosolids stockpiles from Boneo and Somers WwTPs as T1 grade biosolids. This approval was based on a research study that showed that sludge treatment and management processes operating at Boneo and Somers WwTPs exceeded the verification requirements for alternative treatment processes to produce T1 grade biosolids with respect to prescribed faecal bacterial numbers and enteric virus reduction after stockpile storage for a minimum of 1 year [ 17 ].…”

“…This represents a scenario in which pyrolysis is used to reduce biosolids inventory at a particular WwTP where different types of biosolids co-exist at any given time. The details of various biosolids with different plant locations, biosolids production processes, drying methods, number of years stockpiled before pyrolysis, and treatment and contamination grade are highlighted in Table 1 [ 4 , 17 ].…”

A Hybrid Kinetic Analysis of the Biosolids Pyrolysis using Thermogravimetric Analyser

“…In this work, thermogravimetric analysis is employed initially to explore the pyrolysis characteristics of a reference Australian biosolids (obtained from Boneo water recycling plant of South East Water in Victoria) by a method of multi‐heating rates and different temperatures. A comprehensive kinetic study has been performed on this Australian reference biosolids for the first time using a hybrid approach where model‐free methods such as KAS and OFW are used to estimate the activation energy while model‐fitting method such as Coats‐Redfern is used to derive pre‐exponential factor.…”