Micro-aerobic EGSB Research Articles

Research on the Mechanism of Simultaneous and Efficient Removal of Ammonia, NO3 −-N and TN in the Coking Wastewater

Through the sequential-recirculation and cross-recirculation ways, the two-stage micro-aerobic EGSB reactor system was operated to treat the actual coking wastewater. And the removal efficiencies of SCN−-N, CN−-N, NH3-N, NO3 −-N and TN in coking wastewater were investigated, and then the mechanism of simultaneous and efficient removal of NH3-N, NO3 −-N and TN in coking wastewater was also analyzed. The results showed that, using the two-stage micro-aerobic EGSB reactor to treating actual coking wastewater, for the sequential recirculation way and the cross-recirculation way, the removal efficiencies of SCN−-N, CN−-N, NH3-N, NO3 −-N, TN were 98.0%, 91.5%, 81.3%, 30.4%, 24.5% and 97.3%, 97.0%, 92.7%, 92.0%, 70.9%, respectively. And the two-stage micro-aerobic EGSB reactor system could achieve simultaneous and efficient removal of ammonia and TN in the coking wastewater through the cross-recirculation way. For the sequential recirculation two-stage micro-aerobic EGSB reactor system, high SCN−-N and NO3 −-N removal of 94.2% and 90.8% was accomplished in the EGSBI, and high NH3-N removal of 89.8% could attain in the EGSBII. However, high NO3 −-N accumulation in the EGSBII also caused very low TN removal of 24.5% for the two-stage micro-aerobic EGSB reactor system. High SCN−-N removal in the EGSBI could ensure high NH3-N removal in the EGSBII. More importantly, the EGSBI had a very strong ability to support SCN−-N shock. For the cross-recirculation two-stage micro-aerobic EGSB reactor system, the EGSBI could keep simultaneous and efficient removal of SCN−-N, CN−-N, NH3-N, NO3 −-N and TN (93.5%, 92.4%, 84.1%, 92.0% and 73.7%). When using sequential recirculation way, thiocyanate-degrading bacteria could form competitive inhibition to ammonia oxidizing bacteria in the EGSBI, and thus, simultaneous and efficient removal of SCN−-N and NH3-N could not accomplish in the EGSBI. High concentration NO3 −-N in the EGSBI was removed mainly through denitrification. However, through the cross-recirculation way for the two-stage micro-aerobic EGSB reactor system, the effluent recirculation of the EGSBI and/or the EGSBII were changed from simple high NH3-N to mixed recirculation of high NH3-N+high NO3 −-N and/or from high NO3 −-N to high NH3-N+high NO3 −-N, respectively. Consequently, thiocyanate-degrading bacteria, denitrifying bacteria and anammox bacteria could keep high activity at the same time and also the effective coupling of denitrification and anammox bacteria was realized in the EGSBI and EGSBII, and which ensured the simultaneous and efficient removal of SCN−-N, NH3-N and NO3 −-N in the EGSBI and EGSBII, and finally realized the simultaneous and efficient removal of NH3-N, NO3 −-N and TN in the two-stage micro-aerobic EGSB reactor system.

Diatomite strengthen COD and ammonia removal from an micro-aerobic EGSB reactor treating coking wastewater

The performance of one-stage micro-aerobic MAEGSB (OMAEGSB) reactor and two-stage MAEGSB (TMAEGSB) reactor treating actual coking wastewater with and without supplement of diatomite were investigated. The investigation has demonstrated that the two-stage MAEGSB reactor system treating actual coking wastewater could keep high COD and NH3-N removal with supplement of diatomite. With only 24h hydraulic retention time (HRT) (12h for MAEGSB I and 12h for MAEGSB II ), when without diatomite supplement, the TMAEGSB reactor system could attain 72.6% COD average removal and 25.8% NH3-N average removal. However, with 6g•L−1•d−1 diatomite supplement, the TMAEGSB reactor system could keep 84.3% COD average removal and 78.8%-92.8% NH3-N average removal. Such high NH3-N removal efficiency of the TMEGSB was because of the high phenol and thiocyanate (SCN) removal in the MAEGSB I reactor (97.9% and 77.9%) and correspondingly the low influent phenol and SCN concentration for the MAEGSB II reactor (33.9 mg•L−1 and 10.4 mg•L−1). Diatomite supplement could ensure stable and highly efficient phenol and SCN removal in the MAEGSB I reactor. Using TMAEGSB reactor system with diatomite supplement was a simple and high effectively strategy for treatment of actual coking wastewater.

The transformation from anammox granules to deammonification granules in micro-aerobic system by facilitating indigenous ammonia oxidizing bacteria

Granular deammonification process is a good way to retain aerobic and anaerobic ammonia oxidizing bacteria (AOB and anammox bacteria) and exhaust flocculent nitrite oxidizing bacteria (NOB). In this study, to facilitate indigenous AOB growth on anammox granules, by stepwise reducing influent nitrite, anammox granules were effectively transformed into deammonification granules in a micro-aerobic EGSB in 100 days. Total nitrogen removal efficiency of 90% and nitrogen removal rate of 2.3 g N/L/d were reached at stable deammonification stage. High influent FA and limited oxygen supply contributed suppression for Nitrospira-like NOB. In transition stages, Proteobacteria and Chloroflexi were always dominated. Anammox abundance decreased, while AOB abundance grew fast. Anammox bacteria and AOB were dominated by Brocadia fulgida and Nitrosomonas europaea, respectively. Denitrification activity and bacteria existed although without influent organic. The final AOB abundance was about 4.55–13.8 times more than anammox bacteria abundance, with almost equal potential activities.

Kinetic Analysis for COD Removal in Actual Coking Wastewater through an Micro-Aerobic EGSB Reactor

Treatment of actual coking wastewater considered to be difficult by traditional systems. The present study is related to treatment of actual coking wastewater through microaerobic EGSB reactor. The study showed the EGSB reactor could attain about 75% high COD removal. IncreasingVupcould strength COD removal. Moreover, high sludge concentration and profound communal synergism existing within the dense granules were very important. As a result of the kinetic analysis of the EGSB reactor treating actual coking wastewater for COD removal using a modified Stover–Kincannon model, the maximum substrate utilization rate,vmax, half saturation constant,KS, inhibitor constant, KI, actual pollutant removal rate, , and the actual inhibition degree,KS/KIwere determined as 2.65×10-3h-1, 39.57mg.L-1, 415.82mg.L-1, 6.7×10-5h-1.mg-1.L and 0.1(before increasingVup), 7.34×10-3h-1, 19.53mg.L-1, 197.76mg.L-1, 3.7×10-4h-1.mg-1.L and 0.1(after increasingVup), and 9.35×10-3h-1, 6.38mg.L-1, 162.81mg.L-1, 1.47×10-3h-1.mg-1.L and 0.04 (after increasingVupand X), respectively. The inhibition of toxic contaminants in the actual coking wastewater would cause the decreasing of pollutant removal rate, however, enhancing and X (simultaneously optimizing sludge aggregate structure) could strengthen the performance effect.

Thiocyanate Removal from Coking Wastewater through Granular Sludge

To investigate the removal of thiocyanate () in the actual coking wastewater through granular bio-film reactor, two lab-scale granular bio-film reactors (EGSB reactor) (RA and RB) were continuously operated at three stages for about 16 months: anaerobic vs. micro-aerobic for EGSB reactor, varied influent concentrations and varied shock-loading (abrupt and gradual shock-loading) for micro-aerobic EGSB reactor. Compared with anaerobic operation condition, micro-aerobic operation conditions could distinctly strengthen average removal in the EGSB reactor treating actual coking wastewater (47.8% vs.5.3%). At micro-aerobic operation conditions (only with 2000-5000ml·min-1 air flow rate in the external aeration column), with 12h HRT and varied influent concentrations of 200-540mg·L-1, the EGSB reactor could always keep very high removal of 87.6%-94.1%. Microaerobic EGSB reactor had very strong ability of supporting load shock. During the whole operation stage of continuous loads shock (for about 60 days)(from 0.32kgSCN·m-3·d-1 to 1.08 kgSCN·m-3·d-1), removal ability showed a constantly increasing tendency. Micro-aerobic EGSB reactor was a simple and high effectively treatment strategy for the in the actual coking wastewater, and meanwhile high COD, ammonia, phenol and cyanide removal was also kept in the micro-aerobic EGSB reactor.