Deterioration Of Phosphorus Removal Research Articles

Disintegration and re-granulation of aged algal-bacterial aerobic granular sludge in wastewater treatment

Long-term stability in practical applications is one of the crucial issues challenging the sustainable operation of aerobic granular sludge (AGS)-based wastewater treatment systems. Numerous attempts have been made to improve its long-term stability, among which introducing microalgae to bacterial AGS systems seems promising. This study investigated and recorded the whole process of disintegration and re-granulation of the aged algal-bacterial AGS in a 42-day operation. The disintegration of granules was signaled by broken structure and more effluent biomass discharge, resulting in deterioration of phosphorus removal from 86 % on day 1 to 7 % on day 20 and some slight decrease in chlorophyll a content. The broken granules were found to be filamentous flocs or granule fragments, and the latter with coexisting microalgae possibly accounted for the re-granulation and system recovery. Large proportions of fragments could be developed into new granules on day 30 under no additional strategy adoption. And the effluent biomass, chlorophyll a content and phosphorus removal can recover to their initial levels within 34 days' operation. Interestingly, organics and ammonia removals were not affected, which kept around 99 % during the whole test period. Results from this study provide a more in-depth understanding of the stability of algal-bacterial AGS and its long-term operation management.

Improvement of partial nitrification endogenous denitrification and phosphorus removal system: Balancing competition between phosphorus and glycogen accumulating organisms to enhance nitrogen removal without initiating phosphorus removal deterioration

The novel partial nitrification endogenous denitrification and phosphorus removal (PNEDPR) process can achieve deep-level nutrient removal from low carbon/nitrogen municipal wastewater without extra carbons. However, its performance is limited by long hydraulic retention time (HRT) and low specific endogenous denitrification rate (rNO2). This study aimed at investigating the effects of two improving strategies on PNEDPR. One was decreasing both anaerobic and anoxic reaction time for shortening HRT from 55 h to 17.5 h. The other was temporarily discharging orthophosphate-rich supernatant for balancing the competition between phosphorus and glycogen accumulating organisms to further raise rNO2 without deterioration of phosphorus removal. Results revealed that, desirable nutrient removal was obtained, as average effluent concentrations of total nitrogen and orthophosphate were 8.4 and 0.5 mg/L with their average removal efficiencies of 86.8% and 90.9%. High-throughput sequencing analysis revealed that, Candidatus_Competibacter conducted nitrogen removal endogenous denitrification and Candidatus_Accumulibacter and Tetrasphaera ensured phosphorus removal.

Effect of the biofilm detachment pattern on biological phosphorus removal in the biological contact oxidation remediation system purifying contaminated source water

Focusing on the deterioration of phosphorus removal caused by biofilm phosphorus accumulation in biological contact oxidation process,the effect of two biofilm detachment patterns on pollutant removal in the system purifying contaminated source water was investigated in this study.The phosphorus removal efficiency reached 46.9% on the 7th day,then declined quickly.After full biofilm detachment (FBD) pattern was applied,the phosphorus removal was effectively improved and higher dissolved phosphate (DP) removal efficiency (30%) was maintained over 30 days,and the saturated adsorption capacity of phosphate in the biofilm reached (318.5±21.5) mgTP m-2.While the phosphorus removal performance was not improved obviously in the system applying surface biofilm detachment (SBD) pattern,and the saturated adsorption capacity of phosphate was only 0.68 times of that applying FBD.It's speculated that the microbial community of biofilm in the re-growing period and pollutant removal performance of the system were significantly affected by different patterns.Results demonstrated that the heterotrophic denitrifying bacteria tended to be suppressed by dissolved oxygen during the beginning of biofilm re-growth after FBD pattern was applied,which benefited the colonization and enrichment of phosphate accumulating organisms.Compared to new filler,higher surface porosity and biocompatibility caused by residual microorganism and its extracellular polymeric substances with FBD pattern favored biofilm re-growth,and the removal efficiencies of ammonium,permanganate index,total nitrogen could recovered quickly.

Sequencing Batch Reactor (SBR)에서 포기시간 변경에 따른 영향 (1) - 영양염류 제거

Abstract The effect of the variation of aeration time on the removal of organics, nitrogen and phosphorus using synthetic wastewater was investigated in sequencing batch reactors (SBRs) which included DNPAOs and DNGAOs. The cycling times in four SBRs were adjusted to 12 hours and then included different aerobic times as 1 hr, 2.5 hr, 4 hr and 5.5 hr, respectively. Four SBR systems have been operated and investigated for over 40 days. Average TOC removal efficiencies were about 71 % in all SBRs. The NH 4+ -N removal efficiency was increased as the increase of aeration time. After changing aeration time, the total nitrogen removal efficiencies of SBRs were shown as 35 %, 85 %, 75 % and 65 %, respectively. Higher phosphorus release and uptake were occurred as the decrease of the aeration time. After all, the overall phosphorus removal efficiency decreased and the deterioration of phosphorus removal was occurred when aeration time was over 4 hr. Denitrification in aerobic conditions was observed, which showed the presence of DNPAOs and DNGAOs. In batch experiments, PAOs were shown as the most important microorganisms for the phosphorus removal in this experiment, and the role of DNGAOs was higher than that of DNAPOs for the nitrogen removal.Key Words :SBR, Aeration time, Nutrient removal, PAOs, DNPAOs, DNGAOS, Batch experiment

Performance evaluation of a modified anaerobic/anoxic/oxic (A 2/O) process treating low strength wastewater

A full scale modified A 2/O process which combined pre-anoxic selector and the staging strategy treating low strength wastewater was investigated. In South China, domestic wastewater is always low in strength due to the high level of groundwater and setting of septic tank at the beginning of wastewater collection system. The results suggested that inadequate denitrification could result in deterioration of phosphorus removal. In addition, influent phosphorus concentration had effect on phosphorus removal. The pre-anoxic selector in modified A 2/O process changed the distribution of nitrogen denitrified in different tanks. Characteristics of 3-stage aeration tanks were also studied. The simplified design of rectangular aeration tank could also perform as plug flow as conventional channel aeration tank. In 3-stage aeration tanks, mixed liquid suspended solid (MLSS) increased from one tank to another, while specific oxygen uptake rate (SOUR) of sludge, chemical oxygen demand (COD) and total phosphorus (TP) removal rate decreased, however ammonia nitrogen (NH 3-N) and nitrate nitrogen (NO 3-N) reaction rate remained constant. Furthermore, high MLSS concentration was not suitable for treating low strength wastewater. Waste sludge discharge could improve removal efficiency of COD, NH 3-N, and TP. Without waste sludge discharge, nitrite accumulated in settler.