Application of Biofilm Carrier in Aerobic Reactors as a Method to Improve Quality of Wastewater Treatment

Nikolay Makisha

doi:10.3390/hydrology8020077

Abstract

The research revealed in the paper considers the improvement of secondary treatment of wastewater in the aerobic reactor to provide removal of organics and nutrients. There were five types of polymer biofilm carriers taken into account initially; however, two of them were decided not to apply due to technological reasons. The main part of the research was divided into three substages to investigate each type of biofilm carrier. According to the literature review, the optimal efficiency may be reached if the carrier filling ratio is 10 to 30% of reactor volume. On this basis, there were three benches launched at each sub-stage with a corresponding filling ratio of 10, 20, and 30%. The fourth reactor at each sub-stage had no floating carrier to control the experiment. The research of all three types of carriers showed the effect of BOD removal in the range of 95–96% for benches equipped with a floating carrier, which can be considered similar to the control bench with the efficiency of 92%. In the case of ammonia nitrogen, the removal control bench showed only 55% of efficiency, while floating carriers helped to increase the efficiency up to 70–86%. Despite obtaining relatively positive results, the research has to be continued to achieve regulation requirements in treatment quality.

Highlights

All methods of secondary wastewater treatment to provide nitrogen removal are based on nitrification and denitrification (N/D) processes that occur with the participation of certain microorganisms, because of which nitrogen compounds are oxidized to nitrites and nitrates, and reduced to nitrogen gas
After settling the mixed liquor in the Hydrology 2021, 8, x FOR PEER REVIsEeWdimentation tank, the effluent was diverted to the sewer, and the activated slud7goef 1f5rom the sedimentary cone was returned to the aerobic reactor using an airlift
After finishing the part of the research, which was described in the paper, the following summary can be made: 1. Polystyrene carrier showed the most efficient removal of BOD from 155 to 8 mg/L and NH4 removal from 22.1 to 3.1 mgN/L with filling ratio 10%; polyvom carrier ensured the best performance with filling ratio of 20% to provide removal of BOD from 161 to 6.7 mg/L and NH4 removal from 26.6 to 4.9 mgN/L; bioballs carrier optimum filling ratio was 20% that allowed removing of BOD from 144 to 6.4 mgBOD/L and NH4 from 22.7 to 4.3 mgN/L

Summary

Introduction

All methods of secondary wastewater treatment to provide nitrogen removal are based on nitrification and denitrification (N/D) processes that occur with the participation of certain microorganisms, because of which nitrogen compounds are oxidized to nitrites and nitrates, and reduced to nitrogen gas. One of the main advantages of these treatment methods is the possibility of their implementation in conventional activated sludge treatment facilities—in aerobic reactors. Nitrification processes require aerobic conditions with a dissolved oxygen content of 2–7 mg/L in water; denitrification processes require anoxic conditions (the presence of dissolved oxygen in an amount of 0.5 mg/L and/or chemically bound) and/or anaerobic conditions in which oxygen is absent. The implementation of N/D processes is possible in biological reactors, and in trickling filters, respectively, both the attached biofilm and suspended form of activated sludge are involved in treatment. It was important to establish and evaluate the impact of various factors on the implementation of nitrification and denitrification, including the concentration of the substrate, temperature, dissolved oxygen concentration (DO), pH, concentration, and nature of toxic substances. [5,6]

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Results

Discussion

Conclusion