Wastewater Treatment Using a Modified Aerobic Sequencing Batch Reactor

Babu, Gaddam Vidya Sagar and Bhattacharyya, Debraj (2018) Wastewater Treatment Using a Modified Aerobic Sequencing Batch Reactor. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

A research is currently being conducted at IIT Hyderabad to develop a containerized wastewater treatment plant. Small- and medium-scale industries and small residential communities prefer containerized wastewater treatment systems over site-built systems. A containerized wastewater treatment plant offers several advantages over site-built system such as – modular design, flexible operation, better quality control, lesser space requirement etc. The most important component of the present containerized treatment system, which is under development, is a modified sequencing batch reactor (SBR) which has a several novel features over conventional SBR. In an SBR, all the major processes of an activated sludge system – equalization, reaction (aeration), and clarification, are incorporated in one single tank, thereby, saving space. The present system offers several operational flexibilities which are essential for developing a containerized wastewater treatment plant. The scope of this thesis is to develop a pilot/field-scale prototype and to study the performance of the system at different operating conditions using a real domestic wastewater. The reactor has been installed at a Common Effluent Treatment Plant near Patancheru and operated at three different cycles – 12, 8 and 6 hrs. Kinetics of biodegradation was studied at these three cycles. A first-order reaction rate was observed. Different wastewater quality parameters like COD, SOC, TN, TP, TSS, VSS were analyzed. It was observed that COD removal was 75-82% using a floating decanter system and 90-94% using a membrane decanter. However, SOC removals were found to be only around 50% which indicates the presence of considerable amount of recalcitrant carbon in the wastewater. TSS and VSS removals are also found to be between 76-82%. Nitrification occurred within the first one hour of the aeration phase which indicates the presence of considerable amount of Nitrifiers in the sludge biomass. Total nitrogen in the treated effluent was between 20 and 25 mg/L at all the three cycles, which is more than the upcoming Government’s regulation of 10 mg/L (yet to be enforced). This implies that further process modification will be necessary to achieve the desired limit. The effluent total phosphorus was, however, always less than 2 mg/L which is the upper limit of discharge. Fluctuations were observed in all the influent parameters over time. However, the effluent parameters at every cycle were fairly stable. Carbon material balance was done in order to determine the percentage (59-65) of conversion of inlet carbon to carbon dioxide. Bacterial analysis was also done in order to see the removal of common bacterial species. The SBR was able to completely remove Salmonella sp. and Staphylococcus aureus sp. when membrane decanter was used. Microalgae (diatom) was introduced into the system at 6-h cycle. and suitable light source was used to enhance nitrogen removal. The increase in removal percentage was marginal. This indicates that further study is required to convert the existing bacteria-based system into a bacteria-algae based system in order to bring down the effluent nitrogen to the desired level (10mg/L).

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