Optimal conditions and nitrogen removal performance of aerobic denitrifier Comamonas sp. pw-6 and its bioaugmented application in synthetic domestic wastewater treatment.

To assess the possibility of using aerobic denitrification (AD) bacteria with high NO2--N accumulation for nitrogen removal in wastewater treatment, conditional optimization, as well as sole and mixed nitrogen source tests involving AD bacterium, Comamonas sp. pw-6 was performed. The results showed that the optimal carbon source, pH, C/N ratio, rotational speed, and salinity for this strain were determined to be succinate, 7, 20, 160 rpm, and 0%, respectively. Further, this strain preferentially utilized NH4+-N, NO3--N, and NO2--N, and when NO3--N was its sole nitrogen source, 92.28% of the NO3--N (150 mg·L-1) was converted to NO2--N. However, when NH4+-N and NO3--N constituted the mixed nitrogen source, NO3--N utilization by this strain was significantly lower (p < 0.05). Therefore, a strategy was proposed to combine pw-6 bacteria with traditional autotrophic nitrification to achieve the application of pw-6 bacteria in NH4+-N-containing wastewater treatment. Bioaugmented application experiments showed significantly higher NH4+-N removal (5.96 ± 0.94 mg·L-1·h-1) and lower NO3--N accumulation (2.52 ± 0.18 mg·L-1·h-1) rates (p < 0.05) than those observed for the control test. Thus, AD bacteria with high NO2--N accumulation can also be used for practical applications, providing a basis for expanding the selection range of AD strains for wastewater treatment.

Mixed nitrifying bacteria culture under different temperature dropping strategies: Nitrification performance, activity, and community.

In this study, the nitrification performance, metabolic activity, antioxidant enzyme activity as well as bacterial community of mixed nitrifying bacteria culture under different temperature dropping strategies [(#1) growth temperature kept at 20 °C; (#2) sharp1 decreased from 20 °C to 10 °C; (#3) growth at 20 °C for 6 days followed by sharp decrease to 10 °C; and (#4) gradual decreased from 20 °C to 10 °C] were evaluated. It was shown that acclimation at 20 °C for 6 days allowed to maintain better nitrification activity at 10 °C. The nitrite oxidation capacity of nitrifiers was significantly correlated with the relative light unit (RLU) (p < .05) and the fluctuation of superoxide dismutase (SOD) enzyme activity (p < .01). With serial #3 showed the highest RLU levels and the least SOD enzyme fluctuation as compared to serials #2 and #4. Throughout the experimental period, Nitrosospira and Nitrosomonas as well as Nitrospira were identified as the predominant ammonia-oxidizing bacteria (AOB) and nitrate-oxidizing bacteria (NOB). The dynamic change of AOB/NOB ratios and nitrification activity in serials #2-#4 demonstrated that AOB recovered better than NOB with long-term 10 °C exposure, and the nitrification performance was mainly limited by the nitrite oxidation capacity of NOB. Applying 6 days acclimation at 20 °C was beneficial for the mixed nitrifying bacteria culture to cope with low temperature (10 °C) stress, possibly due to the maintenance of metabolic activity, antioxidant enzyme activity stability as well as appropriate AOB/NOB ratio.

Effect of different struvite crystallization methods on gaseous emission and the comprehensive comparison during the composting.

This study compared 4 different struvite crystallization process (SCP) during the composting of pig feces. Four combinations of magnesium and phosphate salts (H3PO4+MgO (PMO), KH2PO4+MgSO4 (KPM), Ca(H2PO4)2+MgSO4 (CaPM), H3PO4+MgSO4 (PMS)) were assessed and were also compared to a control group (CK) without additives. The magnesium and phosphate salts were all supplemented at a level equivalent to 15% of the initial nitrogen content on a molar basis. The SCP significantly reduced NH3 emission by 50.7-81.8%, but not the N2O. Although PMS group had the lowest NH3 emission rate, the PMO treatment had the highest struvite content in the end product. The addition of sulphate decreased CH4 emission by 60.8-74.6%. The CaPM treatment significantly decreased NH3 (59.2%) and CH4 (64.9%) emission and yielded compost that was completely matured. Due to its effective performance and low cost, the CaPM was suggested to be used in practice.

Bioaugmentation for treatment of full-scale diethylene glycol monobutyl ether (DGBE) wastewater by Serratia sp. BDG-2.

A novel bacterial strain BDG-2 was isolated and used to augment the treatment of silicon plate manufacturing wastewater that primarily contains diethylene glycol monobutyl ether (DGBE). BDG-2 was identified as a Serratia sp. Under the optimal conditions of 30 °C, pH 9 and DGBE concentration of 2000 mg L(-1), the bioaugmented system achieved 96.92% COD removal after 39.9h. Laboratory-scale technological matching results indicated that, in a biofilm process with the addition of 100 mg L(-1) ammonia and 5 mg L(-1) total phosphorus (TP), 70.61% COD removal efficiency could be obtained in 46 h. Addition of polyaluminium chloride (PAC) to the reactors during the suspension process enhanced the settleability of the BDG-2 culture. Subsequently, successful start-up and stable operation of a full-scale bioaugmented treatment facilities were accomplished, and the volumetric organic load in the plug-flow aeration tank was 2.17 ± 0.81 kg m(-3) d(-1). The effluent COD of the facilities was stable and always below 100 mg L(-1).

Bioaugmentation treatment of PV wafer manufacturing wastewater by microbial culture.

The wastewater of silicon photovoltaic (PV) battery manufacturing contained polyethylene glycol (PEG) and detergents, which possessed the characteristics of high content of organics and low bioavailability, and then resulted in high treatment costs. To address the difficulties of existing treatment facilities in stably meeting discharge standards, eight tons of microbial culture (consisting of Bacillus sp. and Rhodococcus sp.) were added into the aerobic treatment unit. Subsequently, the effectiveness of the microbial culture in small-scale biological wastewater treatment was evaluated, and the operating conditions for engineering applications were optimized. The application study showed that the average chemical oxygen demand (COD) removal efficiency reached 95.0% when the pH value was 7, the gas-water ratio was 28:1, the reflux ratio was 50%, which indicated an increase of 51.2% contrasting with the situation without bioaugmentation. The volume load of the treatment facilities after augmentation increased by 127.9% and could tolerate the COD shock load reached 2,340 mg·L(-1). At last, the effluence met the class I standard of the Integrated Wastewater Discharge Standard (GB8978-1996).

Impact resistance of different factors on ammonia removal by heterotrophic nitrification-aerobic denitrification bacterium Aeromonas sp. HN-02.

To give reference for the application of heterotrophic nitrification-aerobic denitrification bacteria in actual wastewater treatment, the impact resistance of extreme pH, low temperature, heavy metals and high salinity on ammonia removal by a typical heterotrophic nitrifying-aerobic denitrifying bacterium Aeromonas sp. HN-02 was investigated. The results showed that HN-02 demonstrated strong acid- and alkali-resistance. In addition, it remained active at 5°C, and the removal rates of ammonia and COD were 0.90 mg L(-1)h(-1) and 22.34 mg L(-1)h(-1), respectively. Under the same extent of immediate temperature drop, the temperature correction coefficients of ammonia, COD removal rates and cell growth rate were close. Moreover, HN-02 could survive in the solution containing 0.5 mg L(-1) Cu(2+) or 8 mg L(-1) Zn(2+), or 0.5 mg L(-1) of equivalent Cu(2+)-Zn(2+). Furthermore, efficient ammonia removal was retained at salinity below 20 g L(-1), thus it could be identified as a halotolerant bacterium. At last, stronger stress resulted in higher ΔCOD/ΔTN ratio.