Biological Nutrient Removal In Sequencing Batch Reactors Using Fibrous Packing Medium

The sequencing batch reactor (SBR) is perhaps the most promising and viable of the proposed activated sludge modifications today for the removal of organic carbon and nutrients. In a relatively short period, it has become increasingly popular for the treatment of domestic and industrial wastewaters, as an effective biological treatment system due to its simplicity and flexibility of operation. Mechanism and Design of Sequencing Batch Reactors for Nutrient Removal has been prepared with the main objective to provide a unified design approach for SBR systems, primarily based on relevant process stoichiometry. Specific emphasis has been placed upon the fact that such a unified design approach is also by nature the determining factor for the selection of the most appropriate cyclic operation scheme, the sequence of necessary phases and filling patterns for the particular application. The proposed basis for design is developed and presented in a stepwise approach to cover both organic carbon and nutrient removal, domestic and industrial wastewaters, strong and specific wastes. The merits of model simulation as an integral complement of process design, along with performance evaluation of SBR models are also emphasized. Scientific and Technical Report No. 19

In order to control the eutrophication problems, the removal of phosphorus has been increasingly important. The biological phosphorus removal using sequencing batch reactor (SBR) was investigated using simulated municipal wastewater. Experiments were carried out in eight sequencing batch reactors (SBRs) at hydraulic retention time (HRT) of 5 d. The experiment is operated at loading rates (LR) of 5.0, 4.5, 4.0, 3.5 and 3.0 mg/L.d. The mixed cultured growth is increased with the increasing of LR according to the suspended solids readings. The graph of the suspended solid concentration, the phosphorus removal and the chemical oxygen demand (COD) removal is almost same which is increasing by time and loading rate. The higher the loading rate, the higher the value of suspended solid, phosphorus removal and COD removal. LR 5 mg/L.d shows the highest suspended solid (SS) concentration with average value of 846.24 mg/L. The highest value of phosphorus removal is at loading rate 5.0 mg/L.d with average removal of 57.38%. The COD removal is also highest at loading rate 5.0 mg/L.d with average removal of 64.33%. The removal was influenced by the biofilm growth according to the suspended solid readings. The highest SS reading give the highest removal for both phosphorus and COD. According to the Design Expert plotted, the highest phosphorus removal can be achieved at LR 5.0 mg/L with 56.89% removal. Same result in Design Expert for COD removal which give the highest removal of 61.69% at LR 5.0 mg/L.d. As for the SS concentration, the Design Expert determine that the optimum value of SS is at LR 5.0 mg/L.d with the value of 840.92 mg/L.

Simultaneous biological nutrient removal (SBNR) is the removal of nitrogen and/or phosphorus in excess of that required for biomass synthesis in biological wastewater treatment systems where there are no defined anaerobic and/or anoxic zones. The hypothesis is that one or more of three mechanisms is responsible within individual systems: variations in the bioreactor macroenvironment created by the mixing pattern, gradients within the floc microenvironment, and/or novel microorganism activity. Understanding of the mechanisms of SBNR can be expected to lead to improved efficiency and reliability in its application. Preliminary work documented SBNR in 7 full-scale OrbalTM closed loop bioreactors. A batch assay demonstrated that novel microorganism activity was of little importance in SBNR at the three plants tested. While the floc microenvironment likely plays an important role in nitrogen removal in such plants, it cannot explain phosphorus removal. A computational fluid dynamics (CFD) model was developed to elucidate the role of the bioreactor macroenvironment in SBNR. This is the first reported application of CFD to activated sludge biological wastewater treatment. Although the software and computational requirements limited model complexity, it still simulated the creation of dissolved oxygen gradients within the system, demonstrating that the anaerobic zones required for SBNR could occur.

Published as part of the 2001 subscription to Water Science & Technology, Volume 43, Number 3.