Study on the effect and regularity of plating parts cleaning wastewater by enhanced aerobic process with high-density bacterial flora.

In this research, we established an enhanced aerobic biological method utilizing a high-density bacterial flora for the treatment of low-biochemical plating parts washing wastewater. The elucidation of pollutant removal mechanisms was achieved through a comprehensive analysis of changes in sludge characteristics and bacterial community structure. The results demonstrated that throughout the operational period, the organic load remained stable within the range of 0.01-0.02 kgCOD/kgMLSS·d, the BOD5/COD ratio increased from 0.004 mg/L to 0.33 mg/L, and the average removal rates for key pollutants, including COD, NH4+-N, and TN, reached 98.13%, 99.86%, and 98.09%. MLSS concentration remained at 7627 mg/L, indicating a high-density flora. Notably, Proteobacteria, Bacteroidota, and Acidobacteriota, which have the ability to degrade large organic molecules, had been found in the system. This study affirms the efficacy of the intensive aerobic biological method for treating low-biochemical plating washing wastewater while ensuring system stability.

Micro-pressure swirl reactor (MPSR) for efficient COD and nitrogen removal of high-concentration wastewater.

A micro-pressure swirl reactor (MPSR) was developed for carbon and nitrogen removal of wastewater, in which dissolved oxygen (DO) gradient and internal circulation could be created by setting the aerators along one side of the reactor, and micro-pressure could be realized by sealing most of the top cap and increasing the outlet water level. In this study, velocity and DO distribution in the reactor was measured, removal performance treating high-concentration wastewater was investigated, and the main functional microorganisms were analyzed. The experiment results indicated that there was stable swirl flow and spatial DO gradient in MPSR. Operated in sequencing batch reactor mode, distinct biological environments spatially and temporally were created. Under the average influent condition of chemical oxygen demand (COD) concentration of 2,884 mg/L and total nitrogen (TN) of 184 mg/L, COD removal efficiency and removal loading was 98% and 1.8 kgCOD/(m3·d) respectively, and TN removal efficiency and removal loading reached up to 90% and 0.11 kgTN/(m3·d) respectively. With efficient utilization of DO and simpler configuration for simultaneous nitrification and denitrification, the MPSR has the potential of treating high-concentration wastewater at lower cost.

Improving oxygen dissolution and distribution in a bioreactor with enhanced simultaneous COD and nitrogen removal by simply introducing micro-pressure and swirl.

Increasingly, environmental regulations are demanding more exacting chemical oxygen demand (COD) and nitrogen removal from wastewater, which come at a high economic cost. A very simple novel bioreactor, the micro-pressure swirl reactor (MPSR), can improve the dissolution and distribution of oxygen by the introduced micro-pressure swirl. Comparison with a conventional sequencing batch reactor (SBR) over 76 days of operation showed that this method can enhance simultaneous COD and nitrogen removal. By installing an aeration diffuser on one side of the two-dimensional MPSR, a swirl formed in the bioreactor that extended the retention time of the air bubbles. This unique flow regime, combined with the micro-pressure caused by the elevated water surface at the bubble outflow point, resulted in a higher level of dissolved oxygen (DO) in the MPSR. Aerobic and anaerobic zones that created appropriate conditions for simultaneous COD and nitrogen removal also formed in the MPSR. As the organic loading rate increased from 0.29 to 1.68 g COD/(L · day) over the test period, the COD removal efficiencies of the MPSR were generally 10-20 % greater than those of the SBR. In particular, the total nitrogen (TN) removal efficiencies of the MPSR and SBR were 40-50 and 20-35 %, respectively, whereas the TN concentrations in the MPSR effluent were always around 10 mg/L lower than those of the SBR. Further, because of the unique DO distribution, the bacterial species in the MPSR were more diverse and contributed to enhanced TN removal.

Performance of micro-pressure double-cycle coupled membrane integrated bioreactor for the treatment of urban sewage.

Based on the theory of nitrogen and phosphorus removal and technical requirements, a micro-pressure double-cycle bioreactor coupled with membrane components was used to treat municipal wastewater. The method realized the simultaneous removal of organic matter, nitrogen, and phosphorus in the same reactor and had the characteristics of membrane bioreactor process. Results showed that the average removal efficiency of COD, NH+4-N, TN, and TP were 93.74%, 95.1%, 71.85%, and 81.03%, respectively. During operation, Proteobacteria and Bacteroidetes were the main dominant bacteria, and they had complete nitrogen and phosphorus metabolic pathways. Owing to the low protein content in the mixture, the design of film placement in the micro-precipitation zone was conducive to alleviating the membrane pollution caused by the accumulation of protein, thereby improving the effluent quality and extending the service life of the membrane components.

Precise determination of the total nitrogen content in activated sludge by ultrasonic pre-treatment assisted wet method.

The study proposed a method for determining total nitrogen (TN) content in activated sludge by ultrasound pre-treatment assisted wet method. Based on the single-factor experiment, with the TN content as the response value, the response surface methodology was employed to examine the individual and interactive effects of three factors: the dilution multiple of the sludge mixture, ultrasonic time, and ultrasonic power. At the same time, the physico-chemical parameters and the digestion-oxidation parameters were optimised. The results indicated that the optimal parameters were as follows; sludge dilution multiple of 225 times, stirring rate of 400 r/min, ultrasonic time of 22 minutes, ultrasonic power of 720 W, and optimal added volume of potassium persulfate at 8 mL with a digestion time of 40 minutes. The relative standard deviation (RSD) for the parallel determination of TN in sludge samples using ultrasonic pre-treatment assisted wet method was ≤2.77%, with a spike recovery rate of 98.49-101.43%. The method, ultrasonic pre-treatment assisted wet method to determine TN concentration in activated sludge, was simpler to operate, more accurate.

Characterization of a novel micro-pressure double-cycle reactor for low temperature municipal wastewater treatment.

To solve the deterioration of effluent caused by low temperature in urban sewage treatment plant in cold areas, a new type of reactor was proposed, the biochemical environmental and low-temperature operating characteristics of the reactor were studied. Through analysis of flow simulation and dissolved oxygen (DO) distribution when the aeration rate was 0.6 m3/h, it showed that there were many different DO environments in the reactor at the same time, which provided favourable conditions for various biochemical reactions. The operation test showed that the average effluent removal rate of COD, TN, NH4+-N and TP was 92.53%, 74.57%, 89.61% and 96.04%, respectively. And there were a variety of functional bacteria related to nitrogen and phosphorus removal in the system, most of them with strong adaptability at low temperatures. Among the dominant microorganisms, Flavobacterium and Rhodobacter were related to denitrification, Aeromonas and Thiothrix were related to phosphorous removal. Denitrifying phosphorus removal was the main way of phosphorus removal. Picrust2 results showed that the reactor operated well at low temperature, and the regional difference distribution of nitrification genes further confirmed the existence of functional zones in the reactor. The results showed that the Micro-pressure Double-cycle reactor worked well at low temperature, which provided a new idea and way for the upgrading of urban sewage treatment plants in cold areas.

Study on the inhibition of sludge bulking in A2/O coupled system at low temperature by segmented inlet water mode.

This study aimed to propose a segmented influent method to inhibit sludge bulking. The sludge bulking phenomenon was observed in a A2/O coupled system treating municipal wastewater under low temperature (15 ± 0.5)°C. Adopting the segmented inlet water process, the distribution ratio of the inlet flow in the anaerobic zone and the aerobic zone were 2:1 and 1:1, the sludge bulking phenomenon was suppressed. The sludge loading rate (F/M) analysis showed that the F/M of the anaerobic zone with single-point inflow was only 0.15 kg COD·(kg MLSS·d)-1, which was prone to induce sludge bulking. However, the F/M concentration gradient of the system under segmented inlet water conditions was obvious, which could inhibit the sludge bulking caused by low F/M. The effluent removal results showed that the system had high removal rates of COD, NH4+-N, TN, and TP at a flow distribution ratio of 2:1, with average removal rates of 88.85% ± 2.94%, 91.26% ± 6.68%, 76.60% ± 5.60%, and 96.80% ± 2.17%, respectively. This study confirmed that the segment inlet method inhibited sludge bulking, while the flow distribution ratio of 2:1 also ensured efficient pollutant removal capacity of the system.

Simultaneous removal of organic matter and nitrogen by heterotrophic nitrification-aerobic denitrification bacteria in an air-lift multi-stage circulating integrated bioreactor.

This study aimed to propose a novel air-lift multi-stage circulating integrated bioreactor (AMCIB) to treat urban sewage. The AMCIB combined the reaction zone and sedimentation zone, the alternating circulation of activated sludge in separate aerobic and anaerobic environments facilitates the enrichment of HN-AD bacteria. The preliminary study showed that AMCIB had high removal efficiencies for COD, NH4+-N, TN and TP under high dissolved oxygen (DO) concentration conditions, with average removal rates of 93.21 %, 96.04 %, 75.06 % and 94.30 %, respectively. IlluminaMiSeq sequencing results showed that the system successfully cultured heterotrophic nitrification-aerobic denitrification (HN-AD) functional bacteria (Pseudomonas, Acinetobacter, Aeromonas) that played a crucial role in sewage treatment, and Tetrasphaera was the central phosphorus removing bacteria in the system. Functional gene predictions showed that the HN-AD played a dominant role in the system.

Treatment of phosphorus waste water using crystallization method.

Phosphorus is the restrictive factor of water eutrophication and phosphorus removal is the key point to control this phenomenon. It's also important to recover phosphorus resource from wastewater. Crystallization method was used to treat and recycle high concentration phosphorus wastewater, the selection of organic solvent, influence of volume ratio of organic solvent and wastewater, precipitation time and stirring speed on the production of crystal and its structure was investigated. Experimental results indicate that, with ethanol as extractant, under the condition of volume ratio of ethanol to wastewater being 1.5:1 and stirring speed about 200 r/min, crystal precipitated fast with fine crystal shape and purity, phosphorus removal efficiency more than 85% was obtained.

Pilot study on urban sewage treatment with micro pressure swirl reactor.

This study aimed to propose a new type of micro-pressure swirl reactor (MPSR) to treat urban sewage. The MPSR could form a stable swirl in the reactor, and realized the coexistence of anaerobic, anoxic, and aerobic zones in a single aeration tank. The pilot study showed that MPSR achieved high removal efficient of SS, COD, NH4+-N, TN, TP under the conditions of drastic fluctuation in influent quality and temperature, and the average removal rate were 88.58%, 93.32%, 94.47%, 73.19%, 96.16%. The relative high abundance of Thermomonas, Thaurea, and Dechloromonas, etc, guaranteed the denitrification efficiency of the MPSR, and Dechloromonas was the main phosphorus removal bacteria in the system. The study confirmed the rationality of the structural design of the MPSR, and it was excellent in sewage treatment and stability.