Enhancement of bio-S0 recovery and revealing the inhibitory effect on microorganisms under high sulfide loading.

Biodesulfurization is a mature technology, but obtaining biosulfur (S0) that can be easily settled naturally is still a challenge. Increasing the sulfide load is one of the known methods to obtain better settling of S0. However, the inhibitory effect of high levels of sulfide on microbes has also not been well studied. We constructed a high loading sulfide (1.55-10.86 kg S/m3/d) biological removal system. 100% sulfide removal and 0.56-2.53 kg S/m3/d S0 (7.0 ± 0.09-16.4 ± 0.25 µm) recovery were achieved at loads of 1.55-7.75 kg S/m3/d. Under the same load, S0 in the reflux sedimentation tank, which produced larger S0 particles (24.2 ± 0.73-53.8 ± 0.70 µm), increased the natural settling capacity and 45% recovery. For high level sulfide inhibitory effect, we used metagenomics and metatranscriptomics analyses. The increased sulfide load significantly inhibited the expression of flavin cytochrome c sulfide dehydrogenase subunit B (fccB) (Decreased from 615 ± 75 to 30 ± 5 TPM). At this time sulfide quinone reductase (SQR) (324 ± 185-1197 ± 51 TPM) was mainly responsible for sulfide oxidation and S0 production. When the sulfide load reached 2800 mg S/L, the SQR (730 ± 100 TPM) was also suppressed. This resulted in the accumulation of sulfide, causing suppression of carbon sequestration genes (Decreased from 3437 ± 842 to 665 ± 175 TPM). Other inhibitory effects included inhibition of microbial respiration, production of reactive oxygen species, and DNA damage. More sulfide-oxidizing bacteria (SOB) and newly identified potential SOB (99.1%) showed some activity (77.6%) upon sulfide accumulation. The main microorganisms in the sulfide accumulation environment were Thiomicrospiracea and Burkholderiaceae, whose sulfide oxidation capacity and respiration were not significantly inhibited. This study provides a new approach to enhance the natural sedimentation of S0 and describes new microbial mechanisms for the inhibitory effects of sulfide.

A novel technology with precise oxygen-input control: Application of the partial nitritation-anammox process.

Reliable and accurate oxygen-input control, which is critical to maintaining efficient nitrogen removal performance for partial nitritation-anammox (PN-A) process, remains one of the main operational difficulties. In this study, a novel, yet simple system (a simple process for autotrophic nitrogen-removal, SPAN) with precise oxygen-input control was developed to treat ammonium-rich wastewater via PN-A process. SPAN brings oxygen to biomass by circulating water and creating water spray (shower) at the water-air interface, and effectively balances the activities of core functional microorganisms through precise oxygen-input control. The oxygen-input rate is decided by the water circulation rate and shower rate and is measurable and predictable. Therefore, the required amount of oxygen for ammonium oxidation can be precisely delivered to the biomass by adjusting the circulation rate and shower rate. The results of two parallel SPAN reactors demonstrated that during long-term operation, the required oxygen input was precisely and reliably controlled. More than 99% of NH4+-N and 81% - 85% of total nitrogen were stably removed, with anammox bacteria contributing to more than 96% of total nitrogen removal. Anammox bacteria were efficiently enriched to the highest level among the key nitrogen-converting microbial groups, both in terms of abundance (8.17%) and nitrogen-conversion capacity, while ammonium oxidizing bacteria were well controlled to provide sufficient ammonium-oxidizing capacity. Nitrite oxidizing bacteria were maintained stable (relative abundance of 1.08%-1.88%) and their activity was effectively suppressed. This study provided a novel technology, SPAN, to precisely control oxygen input in PN-A system, and proved that SPAN was effective and reliable in achieving long-term high-efficiency nitrogen removal.

Start up of partial nitritation-anammox process using intermittently aerated sequencing batch reactor: Performance and microbial community dynamics.

This study investigated the performance and microbial community dynamics of a start-up method for the partial nitritation-anammox (PN-A) process: start-up from return sludge in an intermittently aerated sequencing batch reactor (IASBR). The robustness of this PN-A IASBR system in achieving long-term efficient nitrogen removal was also investigated. Stable partial nitritation with nitrite accumulation ratio of about 80% was firstly achieved in the IASBR. Then, PN-A process with total nitrogen removal of up to 81.5% was established due to the thriving of anammox bacteria Candidatus Kuenenia resulting from the reduction of the aeration rate. Molecular analysis showed that both bacterial and archaeal communities shifted greatly throughout the start-up stage and the PN-A stage. Besides bacterial genus Nitrosomonas, ammonium-oxidizing archaea (AOA) Candidatus Nitrososphaera with a high abundance of 3.44% also contributed to partial nitritation. Nitrospira was effectively restrained (abundance <1.6%) while methanogens co-existed with the aerobic and anaerobic nitrogen-conversion microorganisms. This study showed that IASBR configuration was efficient in starting up the PN-A process from return sludge, maintaining long-term efficient nitrogen removal and triggering the thrive of AOA.

[Advanced Treatment of Incineration Leachate with O3-BAC and Double O3-BAC].

Ozone-biological activated carbon (O3-BAC) process and double O3-BAC process were respectively used for advanced treatment of the biologically treated effluent of incineration leachate, and their pollutant removal performances were compared. The results showed that the double O3-BAC removed 75.9% ± 2.1% of chemical oxygen demand (COD), 78.8% ± 2.9% of UV254 and 96.8% ± 0.9% of color at ozone dosage of 200 mg x L(-1). The treated effluent was with COD of below 100 mg x L(-1) and color of below 40 times, meeting the emission requirements of GB 16889-2008. At the same ozone dosage, however, the O3-BAC removed 68.2% ± 1.3% of COD, 69.7% ± 0.5% of UV254 and 92.5% ± 1.1% of color. The treated effluent was with COD of around 150 mg x L(-1) and color of about 60 times, failing to meet the emission requirements. Namely, ozone of 290 mg x L(-1) was required by O3-BAC in order to achieve similar pollutant removals as those in double O3-BAC at O3 dosage of 200 mg x L(-1). In double O3-BAC at ozone dosage of 200 mg x L(-1), total phosphorus was removed by 63.5% ± 4.4%, and the phosphorus concentration in the effluent was remained 1 mg x L(-1) or less, directly meeting the emission requirement of GB 16889-2008.

[Removal of mixed waste gases by the biotrickling filter].

A biotrickling filter (BTF) was designed for treating mixed waste gases, which contained hydrogen sulfide (H2S), tetrahydrofuran (THF) and dichloromethane (DCM) at the start-up and steady states. The removal efficiency of H2S and DCM could maintain about 99% and 60%, respectively, and the removal efficiency of DCM was reduced from 90% to 37% with the shortening empty bed retention time (EBRT) form 50 to 20 seconds when the inlet concentrations were 200, 100, 100 mg x m(-3) of H2S, THF, DCM, respectively. In the theoretical study, the biodegradation efficiency of contaminants was H2S > THF > DCM by analyzing the Michaelis-Menten Dynamic model.