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Owing to its widespread and persistent usage, methylene blue (MB) is an environmental substance, mostly found in the printing and dyeing industry that raises concerns in the environment recently by posing significant threat to human life and the ecosystem as a whole. Thus, there is the need to effectively manage and treat the wastewater from these industries before reaching to the available water sources. Ozonation treatment is very efficient in treating printing and dyeing wastewater (MB) and can be greatly improved by using micro-bubble technology. Microbubble dissolution is an effective way to improve the rate of ozone mass transfer. To discover these properties, a method was used to improve the mass transfer of ozone microbubbles, which was used to effectively treat simulated printing and dyeing wastewater. We investigated the effects of pH, water temperature, ozone flow, and other conditions on the dissolution and attenuation properties of ozone in methylene blue microbubble solutions. Treatment of simulated printing and dyeing wastewater (methylene blue) was investigated under various initial pH and ozone flow rates. A catalytic exhibition was performed towards the decolorization of methylene blue (MB) concentrations and the corresponding COD removal efficiency. Ozone depletion and pH levels played key roles in MB degradation. Under high pH level of 11.01, the rate of removal of COD was 93.5%. Ozone dosage also has direct effect on COD removal efficiency and decolorization. Higher ozone flow rates, 0.4 L/min and 0.5 L/min recorded more than 94% degradation of COD thus very effective and efficient. Also, ozone flow rates 0.3 L/min, 0.4 L/min and 0.5 L/min with initial pH, 7.03, 6.63 and 6.36 decreased to 3.43, 3.49 and 3.44 after reaction processes which clearly shows that with high ozone dosage, pH reduces considerably.

In order to ascertain the characteristics of two different biofilm reactors and its efficiency, the influence of pH, DO and HRT in the clean-up of COD, NH3-N and TP as well as determining the relationship between microbial community structures and its performance of the two biofilm reactors. This study made use of a biological contact oxidation process system in a small-scale experiment to treat domestic sewage. This contemporary study examined the performance of two different fillers thus, BCF and MBBF in removal of organic pollutants from domestic wastewater as a novel technique of BCOP for sewage treatment. Two self-made biological contact biofilm reactors were used for the experiment: BCR (mounted with BCF) and MBBR (mounted with MBBF). After the biological treatment, the COD concentration of effluent could stay below 350 mg/L. The study analyzed the effects of hydraulic residence time (HRT) on COD, ammonia nitrogen (NH3-N), and total phosphorus (TP) as well as the characteristics of each biofilm filler. The optimal HRT was 12 h; at that time, the experimental results indicated that BCF had higher removal efficiency of chemical oxygen demand, ammonia-nitrogen and total phosphorus at 50%, 96%, and 86%, respectively. Great contribution was made by the process by means of improving the biodegradability of domestic sewage and reducing sludge emergence via fermentation in the biological reactor.

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