Treatment of industrial effluents and analysis of their impact on the structure and function of microbial diversity in a unique process

Excessive nutrients released from factories along with pollutants are the key reason for the dense growth of plants in water bodies, which poses a serious environmental problem in many developed and developing countries. The dairy and fertilizer industries produce a large amount of wastewater loaded down with organics and nutrients including phosphate and nitrate. Most of the wastewater treatment plants treat these two nutrients in different procedures in separate setups, which is time consuming and expensive. Nitrogen contamination is being treated by nitrification and denitrification processes whereas phosphate in the wastewater is treated by enhanced biological phosphorus removal (EBPR).

EBPR process is preferred for phosphorus treatment but this method was found to be inefficient for removing nitrogen entities. In one of the previous studies, a low oxygen phase was added to the conventional EBPR method for treating nitrogen entities. But it made the process more complicated and expensive.

In this study, researchers have developed a process known as anoxic-aerobic single-cell Sequential Batch Reactor (AnASBR) which have many benefits over the conventional and the modified EBPRs. This process is capable of treating the industrial effluent polluted with nitrate along with phosphate and organics. Also this process has the potential to change the diversity as well as the metabolic adaptation of the involved microorganism radically than that of the conventional process.

In order to help AnASBR as a long-term and safe alternative for the treatment of wastewater rich in nutrients, this study aimed at achieving the following.
I. Optimization of the AnASBR to achieve maximum removal of nutrients and Chemical Oxygen Demand (COD).
II. Treatment of two industrial effluents in the optimized AnASBR
III. In-depth study of microbial diversity and putative metabolic potential of the microbes.

Two sequential batch reactors (SBR) with Anoxic-Aerobic process (AnAP) were established for the treatment of effluent from two industries; phosphate fertilizer (AnASBR_PPL) and dairy industry (AnASBR_DW). Up to 90% and ~80% of COD removal were achieved in AnASBR_PPL and AnASBR_DW, respectively. Interestingly change in influent had an impact on bacterial diversity. All reactors were filled from the parent SBR with the same deposit, while the population remained largely unchanged, the population’s evenness changed drastically to get accustomed to the changing climate. Rhodocyclales was accounted for 66% of the population in AnASBR-PPL and 22% in AnASBR-DW. Rhodocyclales was widely reported as the significant phosphate accumulator in full-scale EBPR systems.

AnASBRs observed the predominance of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia. The identity of the core group members remained relatively constant at steady-state activity, but their relative abundances in both reactors changed considerably as a result of varying industrial effluent. However, population of few strains such as Lactobacteriales, Enterobacteriales changed drastically with respect to the influent, as these strains were predominant in AnASBR_DW but not present in AnASBR_PPL.

A novel Anoxic-Aerobic Process (AnAP) that eliminated the anaerobic cycle was designed and worked for the simultaneous remediation of industrial effluent phosphate, nitrate, and chemical oxygen demand (COD). COD and nutrients in the effluents were successfully remediated simultaneously in the optimized reactors. Partial sludge granulation was observed in both SBRs which makes it easier for the microbes to consume a very small amount of phosphate and nitrate under aerobic conditions. The metagenomic study revealed denitrifying phosphate accumulating organisms (DNPAOs) as the dominant group of bacteria in both the reactors. PAOs were also present in the consortium but not in dominance. Diverse micro-flora ensured robustness and performance stability in the process of high strength and various industrial effluent treatments. This study proved the efficiency of the new AnASBR as an alternative system that is energy efficient with higher ease of operation for the treatment of real industrial effluents without fail.

Reference: https://pubmed.ncbi.nlm.nih.gov/32148310/

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