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In order to identify appropriate environmental conditions and media components that are either essential or that enhance its growth and Microbial induced calcium carbonate precipitation (MICP) activity, in this study, a series of experiments were conducted to investigate the effects of media components and oxygen conditions on the growth rate and MICP activity of Lysinibacillus sphaericus strain MB 284. From these experiments, it was observed that aerobic conditions could lead to increased calcium carbonate production and up to three times faster growth rates by strain MB284 when compared to anoxic conditions. It was also determined that considering the measured growth rate, final biomass concentration, ureolysis activity, amount of calcium carbonate precipitation, and cost of media components for designing undefined culture media for industrial applications, yeast extract is the most economically appropriate option. In our attempts to grow strain MB284 in urea, sucrose, and ammonium acetate as its sole carbon source in minimal media, it was observed it is auxotrophic and that casamino acids and casein are essential for its growth. Even though our experiments agree with the literature that the addition of urea enhances the growth and MICP activity of L. sphaericus, it was discovered that when the initial urea concentration was greater than 3 g/l, the growth rate of strain MB284 can be temporarily inhibited until enough cells and urease are produced. These results reveal that the growth and MICP activity of strain MB284 during its application for bio-self healing can be highly dependent on environmental and nutrient conditions.

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Methylene blue (MB) is a toxic and colorful organic matter that exists in the wastewater of textile industries. Difficult biodegradability of MB causes biological treatment methods that cannot sufficiently biodegrade it. In photoelectrocatalytic (PEC) methods, by converting the radiation energy to the electricity, MB is degraded efficiently in the anolyte chamber. Using the ultrafiltration (UF) membrane rather than a high-priced cation exchange membrane (CEM) decreases the cost of the PEC pilot. Therefore, in this study, different dependent and independent variables that affect the performance of the PEC are investigated to evaluate the technical feasibility of using ultra-filtration membrane as a separator of anode and cathode chambers. The results demonstrate an increase in the anolyte MB concentration up to 15 mg/l augments the PEC performance. In the best condition, the MB, turbidity, and color removal percent are 51.56%, 65.62%, and 64.19%, respectively, and produced power is 1.075 μW when the anolyte MB concentration, the pH, and the illumination density are 15 mg/l, 3, and 12 W, respectively. Also, the results indicate the removal percentage of the MB, turbidity, and color in either anolyte or catholyte rises in the anolyte acidic conditions and higher illumination densities. Besides, the changes in the EC and pH of anode and cathode chambers during the experiment are investigated, and finally, the relations between MB, color, and turbidity removal percentage are evaluated. As a result, it is found that the UF membrane is a suitable candidate to be used in PEC pilots.

The performance of a sequencing batch bioreactor (SBR) coupled with a membrane bioreactor (MBR) for treatment of hypersaline produced water by insertion of a halophilic bacterial consortium was tested at three different organic loading rates (OLRs): 1, 2 and 4 (kg chemical oxygen (O2) demand (COD)/m3)/d. Four total dissolved solids (TDS) concentrations (20, 50, 80 and 120 g/l) were investigated in this study. At different TDS concentrations and OLRs, COD removal was found to be efficient at 91·3–99·5% and the amount of mixed liquor suspended solids (MLSS) varied from 4·61 to 9·88 g/l. The amounts of COD removal and MLSS increased with increased OLRs and decreased in hypersaline concentrations. Increases in TDS had a negative effect on membrane flux and fouling rates, but, in this hybrid system, the reduction in flux with increase in TDS was minor, while high-quality treated water was produced from the immersed membrane.