In this study, use of microalgae for secondary and tertiary wastewater treatment was evaluated. First phase of the study investigated the ability of microalgae to remove nutrients, organic carbon and indicator bacteria from secondary effluents and centrate.For secondary wastewater and centrate, the reductions in soluble concentrations of total nitrogen, phosphorus, and COD were 27, 51.7, 29.5% and 49.4, 78.6. 32.8%, respectively. Total coliform reduction was greater than 99.5%. The second phase investigated the use of microalgae in combination with activated sludge system. Soluble COD removal improved from 1.5% for sample A (activated sludge) to 65.6 and 77.8% for samples B (activated sludge and microalgae) and C (microalgae). Ammonia was removed by 99.9% for B and C, while the removal was 46.4% for A. Total dissolved phosphorus was removed by 81.3 and 73.2% for B and C, but there was no reduction in dissolved phosphorus for A.iii

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This study investigated the impact of lime stabilization on the fate and transformation of AgNPs. It also evaluated the changes in the population and diversity of the five most relevant bacterial phyla in soil after applying lime-stabilized sludge containing AgNPs. The study was performed by spiking an environmentally relevant concentration of AgNPs (2 mg AgNPs/g TS) in sludge, applying lime stabilization to increase pH to above 12 for two hours, and applying lime-treated sludge to soil samples. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) were used to investigate the morphological and compositional changes of AgNPs during lime stabilization. After the application of lime stabilized sludge to the soil, soil samples were periodically analyzed for total genomic DNA and changes in bacterial phyla diversity using quantitative polymerase chain reaction (qPCR). The results showed that lime treatment effectively removed AgNPs from the aqueous phase, and AgNPs were deposited on the lime molecules. The results revealed that AgNPs did not significantly impact the presence and diversity of the assessed phyla in the soil. However, lime stabilized sludge with AgNPs affected the abundance of each phylum over time. No significant effects on the soil total organic carbon (TOC), heterotrophic plate count (HPC), and percentage of the live cells were observed.