Saltwater addition negatively impacted the settling properties of the activated sludge in a sequencing batch reactor, which in turn caused the effluent quality and the dewatering properties to deteriorate. Experiments showed that increasing sodium ion concentrations above 1 meq/L interfered with bio‐flocculation by ion exchange of calcium ions displaced by sodium in mixed liquor flocs, causing increases in the sludge volume index, total suspended solids, and chemical oxygen demand concentrations of the final effluent and in the times of the time to filter test of the mixed liquor. Experiments were also conducted to reverse mixed liquor de‐flocculation by adding calcium ions in wastewater with different sodium chloride concentrations and a positive relationship was found between calcium ion added and improved effluent quality. Calcium ion concentrations above 1.6 meq/L proved to be beneficial for adhesion of microbial aggregates leading to the formation of stable flocs and improved sludge dewatering by reversing the ion exchange phenomenon observed with sodium concentrations above 1 meq/L. Monovalent‐to‐divalent ratios did not provide predictive information on de‐flocculation. Hence, individual ion concentrations in addition to monovalent‐to‐divalent cation ratios are important in the onset of de‐flocculation effects while a system‐specific concentration threshold was measured under which no adverse effects were observed. Practitioner points The adverse effects of varying concentrations of sodium chloride on the biological process affecting bioflocculation and effluent quality. Impact of sodium on the health of the mixed liquor as well as on dewatering processes. Prediction of sea level rise due to climate change will impact utilities situated along the coast with saltwater intrusion problems. Management of dewatered flows containing saltwater from onsite construction Identify management practices to reduce the impact of saltwater on the wastewater treatment plant.

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A study was conducted to analyze the effect of solubilization due to thermal hydrolysis pretreatment on the microbial population responsible for anaerobic digestion at mesophilic temperature. Metagenomic and microbial population analysis was done on digesters receiving sludge with and without thermal hydrolysis pretreatment. The digester receiving thermal hydrolysis pretreatment was stable at lower detention times and showed a shift in microbial population with predominance of methane-producing population in comparison to conventional digesters receiving no thermal hydrolysis pretreatment. Among methanogens, Methanosarcina showed dominance in the thermal hydrolysis pretreatment digester. Digesters with no thermal hydrolysis pretreatment had a mixed culture of acid-producing bacteria and methane-producing archaea, with almost equal proportion of methane-producing Methanobacterium and Methanosarcina. Kinetic parameters showed high growth and substrate utilization rates in digester receiving thermal hydrolysis pretreatment.

A study was conducted to determine the effect of solubilzation due to thermal hydrolysis pretreatment on the microbial population responsible for anaerobic digestion at mesophilic temperature. Metagenomic and microbial population analysis was done on digester receiving thermal hydrolysis pretreatment as well as on conventional digester receiving no thermal hydrolysis pretreatment. The digester receiving thermal hydrolysis pretreatment was stable at lower detention times and showed shift in microbial population with predominance of methane producing population in comparison to conventional digesters receiving no thermal hydrolysis pretreatment. Among methanogens, Methanosarcina showed dominance in the THP digester. Conventional digesters had mixed culture of acid producing and methane producing population, with almost equal population of methane producing archaeal population -Methanobacterium and Methanosarcina. Kinetics showed high growth and substrate utilization rates in pilot digester receiving THP.