Granular indigenous microalgal-bacterial consortium for wastewater treatment: Establishment strategy, functional microorganism, nutrient removal, and influencing factor.

Granular indigenous microalgal-bacterial consortium (G-IMBC) system integrates the advantages of the MBC and granular activated sludge technologies, also with superior microalgal wastewater adaptation capacity. In this review, the concept of IMBC was firstly described, followed by its establishment and acclimation strategies. Characteristics and advantages of G-IMBC system compared to other IMBC systems (i.e., attached and floc IMBC systems) were then introduced. Moreover, the involved functional microorganisms and their interactions, as well as nutrient removal mechanisms were systematically and critically reviewed. Finally, the influencing factors including wastewater characteristics and operation factors were discussed. This study aims to provide a comprehensive up-to-date summary of the G-IMBC system for sustainable wastewater treatment.

Simultaneous improvements on nutrient and Mg recoveries of microalgal bioremediation for municipal wastewater and nickel laterite ore wastewater.

Effects of different mixing ratios between synthetic municipal wastewater (MW) and magnesium (Mg2+)-enriched nickel laterite ore wastewater (NLOWW) on growth of Chlorella sorokiniana (C. sorokiniana), photosynthetic activities, cellular biocomposition, nutrient and Mg2+ removal were investigated in photobioreactors. In the culture without NLOWW, wrinkled cells were observed with low biomass production. The culture mixed with 0.13% NLOWW obtained 1.89-fold higher biomass yield, 3.77-fold enhanced photosynthetic activity (Fv/Fm value), and improved nutrient removal (nitrogen by 102.2%, phosphorus by 39.3%). However, excessive Mg2+ at 100% NLOWW produced highest reactive oxygen species suppressing microalgal growth. The Mg2+ removal capacity increased with NLOWW loading. Moreover, microalgal assimilation primarily contributed to nutrient removal while absorption was the dominant Mg2+ removal pathway. Carbohydrate content in biomass increased with Mg2+ loading. Finally, the approach for MW/NLOWW treatment was demonstrated as economically feasible with revenue of $75.6 per kilogram biomass through a comprehensive economic model.

Evaluation of upgrading a full-scale activated sludge process integrated with floating biofilm carriers.

This study evaluated the performance of a full-scale upgrade of an existing wastewater treatment plant (WWTP) with the intermittent cyclic extended aeration system (ICEAS), located in Qingdao, China. The ICEAS system was not able to meet effluent standards; therefore, a series of modifications and control strategies were applied as follows: (1) floating plastic carriers were added to the tank to aid biofilm formation; (2) operation parameters such as mixing and aeration time, feeding rate, and settling time were adjusted and controlled with a real-time control system; (3) a sludge return system and submersible water impellers were added; (4) the aeration system was also improved to circulate carriers and prevent clogging. The modified ICEAS system exhibited efficient organic and nutrient removal, with high removal efficiencies of chemical oxygen demand (89.57 ± 4.10%), NH4(+)-N (95.46 ± 3.80%), and total phosphorus (91.90 ± 4.36%). Moreover, an annual power reduction of 1.04 × 10(7) kW·h was realized as a result of these modifications.

Full-scale demonstration of step feed concept for improving an anaerobic/anoxic/aerobic nutrient removal process.

A small wastewater treatment plant (WWTP) failed to meet effluent requirements of the first-A discharge standard in China, with the anaerobic/anoxic/oxic (A/A/O) process treating municipal and partial industrial wastewater. Thus an A/O step feed process (Anoxic/oxic/anoxic/oxic/anoxic/oxic) with floating plastic carriers in aerobic units was proposed to improve nutrient removal within the existing WWTP. Four main reform strategies were applied: (1) the original influent was divided into three streams which led into corresponding anoxic units; (2) floating plastic carriers were placed in the second and third oxic units; (3) nitrified liquid recycling was omitted; (4) channel shapes and sizes were adjusted between adjacent units to prevent backflow. After these modifications were implemented, the total nitrogen and phosphorus concentrations in the effluent were reduced from 20.8 to 14.2mg/L, and from 1.89 to 0.57 mg/L, respectively. Moreover, annual electricity consumption in the WWTP was reduced by 245 MWh as a result of these modifications.

[Optimization of a modified UCT step feed process treating municipal wastewater].

A pilot-scale modified UCT step feed process was proposed to treat the municipal wastewater with lower COD/N in a large-scale wastewater treatment plant. Effects of influent distribution ratios and nutrients ratios (COD/N, COD/P and TN/P) on nutrients removal capabilities were importantly investigated. The removal mechanisms of organics and nutrients and sludge characteristics were ultimately discussed. According to the continuous experiments, the stable and high process performance was obtained. The average COD removal efficiencies and effluent concentration of (83.8 +/- 3.86)% and (43.7 +/- 8.35) mg/L were achieved in the influent COD loading of 0.79-0.93 kg/(m3 x d). The COD removal in anaerobic and anoxic zones accounted for 60.2% - 76.2%. With the influent distribution ratio of 40%: 30%: 30%, as much as 88.2% of TN removal efficiency was observed. It should be considered the removal of 32.8% through simultaneous nitrification and denitrification process. The average effluent NH(4+)-N and TN were (0.21 +/- 0.20) mg/L and (7.90 +/- 1.27) mg/L, respectively. It was extremely important that as much as 32.6% - 39.5% of the denitrifying phosphorus accumulation organisms contributed to the high phosphorus removal efficiency of 97.2%. A linear positive relationship was observed between nitrogen removal efficiency and COD/N in the range of 4.64 and 7.41 (R2 = 0.96). Phosphorus removal efficiency was found to be a function of the influent COD/P and TN/P, varying from 35.0 to 92.5 and from 6.24 to 12.5, respectively (R2 = 0.87 and R2 = 0.89). In addition, the great sludge settleability was obtained with the mean SVI of (82.6 +/- 4.99) mL/g.

Enhanced nutrient removal in three types of step feeding process from municipal wastewater.

An anoxic/oxic step feeding process was improved to enhance nutrient removal by reconfiguring the process into (1) anaerobic/anoxic/oxic step feeding process or (2) modified University of Capetown (UCT) step feeding process. Enhanced nitrogen and phosphorus removal and optimized organics utilization were obtained simultaneously in the modified UCT type with both internal and sludge recycle ratios of 75% as well as anaerobic/anoxic/oxic volume ratio of 1:3:6. Specifically, the UCT configuration and optimized operational conditions lead to the enrichment of denitrifying phosphorus removal microorganisms and achieved improved anaerobic P-release and anoxic P-uptake activities, which were beneficial to the denitrifying phosphorus removal activities and removal efficiencies. Due to high mixed liquor suspended solid and uneven distributed dissolved oxygen, 35% of total nitrogen was eliminated through simultaneous nitrification and denitrification process in aerobic zones. Moreover, 62 ± 6% of influent chemical oxygen demands was involved in the denitrification or phosphorus release processes.

Enhanced nutrient removal in a modified step feed process treating municipal wastewater with different inflow distribution ratios and nutrient ratios.

A pilot-scale modified step feed process was proposed to enhance organics and nutrient (N and P) removal performance from municipal wastewater. It combined University of Cape Town (UCT) and step feed process. Effects of inflow distribution ratios and nutrients ratios were investigated. The highest removal efficiencies of 89% for chemical oxygen demanding (COD), 88% for total nitrogen (TN) and 93% for phosphorus were obtained, respectively, at the inflow distribution ratio of 40:30:30%. The phosphorus removal exhibited an upward trend with the increasing of influent COD/P and TN/P, and the nitrogen removal had a positive correlation with influent COD/TN. In addition, aerobic simultaneous nitrification and denitrification and anoxic denitrifying phosphorus uptake made a distinct contribution to enhance nutrient removal. The proposed system was demonstrated to be an attractive enhanced biological nutrient removal process for wastewater treatment plants due to relatively high nutrient removal, robust sludge settleability and energy savings.