•A pilot-scale system was built to treat cellulosic ethanol biorefinery wastewater.•The combined CSTR-IC-SBR system with ozone-enhanced unit showed 85% of COD removal.•The ozone improved the biodegradability of anaerobic effluent from 0.15 to 0.33.•The shortcut biological nitrogen removal process was developed and operated stable.The treatment of wastewater from a cellulosic ethanol biorefinery presents special challenges. A pilot-scale process that utilized a continuous stirred tank reactor (CSTR), an internal circulation reactor (IC), and a sequencing batch reactor (SBR) with ozone oxidation enhancement was developed for the treatment of this challenging biorefinery wastewater. The CSTR and IC were used for COD removal through anaerobic treatment, and the SBR process was used for nitrogen removal through alternating aerobic nitrification and anaerobic denitrification. The combined process removed 85% of chemical oxygen demand (COD) and 80% of ammonium. The corresponding effluent concentrations of COD and ammonium were 1591 ± 226 mg/L and 61 ± 8 mg/L, respectively. Ozonation enhanced the biodegradability of the anaerobic effluent, the BOD5/COD ratio of which increased from 0.15 ± 0.02 to 0.33 ± 0.05. The BOD5/COD ratio of the effluent from the SBR was 0.07 ± 0.01, which indicated the effluent was no longer treatable using a biological process. A total sulfate removal efficiency of 65% was obtained through an alternating anaerobic and aerobic process, and the final effluent sulfate concentration was 217 ± 10 mg/L.Download high-res image (167KB)Download full-size image

There are three key aspects of substrate effect on anaerobic ammonia oxidizing (anammox) bacteria: (1) substrate concentration-based nitrogen loading rate (NLR), (2) hydraulic retention time (HRT)-based NLR and (3) nitrite/ammonia ratio. The first part has been fully investigated in the past, while the latter two are still not properly understood. In this study, two types of substrate effects (HRT-based NLR and nitrite/ammonia ratio) were experimentally proved based on a 226 day operation of a sequencing batch biofilm reactor (SBBR) that was dominated by anammox bacteria. A modified first-order substrate removal kinetic model was developed, which efficiently fits to the experimental results. Decreasing HRTs from 72 h to 6 h were applied to the SBBR, and the HRT = 6 h was proven to be optimal for the highest nitrogen removal rate (NRR) (1.62 kg N m−3 d−1 and the total nitrogen removal efficiency >90%). In addition, the influent nitrite/ammonia ratio of 1.2 resulted in a stable and effective operation of anammox SBBR with an improved ammonia removal efficiency (by 17%) and an enhanced NRR (from 0.93 kg N m−3 d−1 to 1.14 kg N m−3 d−1).

A natural origin adsorbent was prepared by sawdust and beta-cyclodextrin (β-CD) for the removal of an organic compound (aniline) during water pollution accidents. The results of BET, SEM and FTIR analyses indicated that β-CD attaches on the sawdust surface and forms an organic film. Batch tests show that the optimum pH for aniline adsorption is in the range of 4–8. Adsorption equilibrium is achieved in 30 minutes, and the adsorption kinetics follows a pseudo-second-order kinetic model. The Langmuir model appears to fit the isotherm data better than the Freundlich model at 15 °C compared with that at 30 °C and 45 °C. The maximum adsorption capacity is estimated to be 84.03 mg g−1 at 15 °C (R2 > 0.99). The negative value of the standard entropy (ΔHo) and standard free energy (ΔGo) indicates an exothermic and spontaneous nature of the adsorption interaction. Moreover, the results of FTIR suggest that the formation of an inclusion complex between the β-CD and aniline molecules through host–guest interactions enhances the adsorption capability.

Microbes are vital to the earth because of their enormous numbers and instinct function maintaining the natural balance. Since the microbiology was applied in environmental science and engineering more than a century ago, researchers desire for more and more information concerning the microbial spatio-temporal variations in almost every fields from contaminated soil to wastewater treatment plant (WWTP). For the past 30 years, molecular biologic techniques explored for environmental microbial community (EMC) have spanned a broad range of approaches to facilitate the researches with the assistance of computer science: faster, more accurate and more sensitive. In this feature article, we outlined several current and emerging molecular biologic techniques applied in detection of EMC, and presented and assessed in detail the application of three promising tools.

With the unique cell compartmentalization and the ability to simultaneously oxidize ammonium and reduce nitrite into nitrogen gas, anaerobic ammonium-oxidizing (anammox) bacteria have challenged our recognitions of microorganism. The research conducted on these bacteria has been extended from bench-scale tryouts to full-scale reactor systems. This review addresses the recently discovered versatile properties of anammox bacteria and the applications and obstacles of implementing the anammox process in ammonia-rich wastewater treatment. We also discuss the merits and drawbacks of traditional and anammox-based processes for nitrogen removal and suggest areas for improvement.

A laboratory anaerobic membrane bioreactors (AnMBRs) (10 L volume) was operated at 30 °C and fed with artificial sewage containing 30% protein at COD loading rate 5.1 kg/m3-d to investigate membrane fouling with two membranes. Biomass attached to the membrane surface and formed a foulant layer on the membrane. The foulant layers from polyvinylidene fluoride ultrafiltration membranes coated with PEBAX (cPVDF) and an uncoated polyetherimide (PEI) ultrafiltration membranes were analyzed and compared to suspended biomass in the reactor, using terminal restriction fragments (T-RFs) of the 16S rRNA gene and a clone library. One species of OP11 bacteria was present at high relative abundance in the foulant layers of both membranes. By contrast, Bacteroidetes and Firmicutes (LGC) species were present at low relative abundance in the foulant layers but high relative abundance in the suspended biomass. Similar differences were observed for other species. The results suggest that some minority species like OP11 play a direct role in fouling by attaching to the membrane surface while others, including some that likely play a major role in the metabolism of influent organics, play a less important or indirect role. In the AnMBR, the EPS was predominately proteinaceous. EPS and microbial cells of the foulant layer contributed to membrane fouling. The results also indicate that fouling of PEI was faster than cPVDF and this reaffirm the importance of the membrane material in fouling.Research highlights▶ An anaerobic membrane reactor (AnMBR) was tested for biofouling by using polyvinylidene fluoride ultrifiltration membrane coated with PEBAX (cPVDF) vs an uncoated polyetherimide (PEI) ultrafiltration membrane. ▶ OP11 bacteria were present at high abundance in the fouling layers of both membranes. Other species were present at high abundance in suspended biomass. ▶ Extracellular polymeric substance (EPS) in AMRR was mainly proteinaceous. Both EPS and bacterial cells, especially OP11, caused biofouling. ▶ Fouling of PEI membrane was faster than cPVDF.

A kinetic model for shortcut nitrification−denitrification process with sequencing batch reactor (SBR) was developed. To test this model, the kinetic parameters of the model including maximum specific rates and half-maximum rate concentrations for shortcut nitrification and denitrification were estimated from the results obtained from a laboratory-scale SBR fed with a soybean curd processing wastewater (400−800 mg COD L−1, 50−65 mg NH4+-N L−1) at 26 °C. In the nitrification step, two DO levels (0.5 and 3.5 mg L−1) were tested and the predicated nitrification rates under different NH4+-N concentrations using this model fit well with correlation coefficient R = 0.9902. In the denitrification step, the process of nitrite removal was close to a zero-order reaction if the concentration of electron donor was not so low (COD > 100 mg L−1), and concentrations of nitrite and organic matter (as COD) had limited effect on denitrification rate. The model can be used to predict nitrogen removal performance with different influent NH4+-N and COD concentrations and under various DO concentrations.

•Integrated anaerobic membrane bioreactor was used to treat benzothiazole wastewater.•The accumulation of VFAs increased with the addition of benzothiazole.•The biodegradation of benzothiazole was increased by the adaptation of microbes.•Acetotrophic methanogens were more sensitive to the addition of benzothiazole.This study investigated the impact of benzothiazole on the performance and microbial community structures in an integrated anaerobic fluidized-bed membrane bioreactor fed with synthetic benzothiazole wastewater (with gradually increasing doses of benzothiazole (1–50 mg/L)). The addition of benzothiazole had an adverse effect on volatile fatty acids accumulation (from 10.86 mg/L to 57.83 mg/L), and membrane fouling (service period from 5.9 d to 5.3 d). The removal efficiency of benzothiazole was 96.0%. Biodegradation was the major benzothiazole removal route and the biodegradation efficiency obviously improved from 25.7% to 98.3% after adaptation. Sludge 1 (collected on day 58 without benzothiazole) and sludge 2 (collected on day 185 with 50 mg/L benzothiazole) were analyzed using the Illumina®MiSeq platform. The most abundant genera were Trichococcus (43.1% in sludge 1) and Clostridium sensu stricto (23.9% in sludge 2). The dominant genus of archaea was Methanosaeta (90.3% in sludge 1 and 80.8% in sludge 2).

The constructed wetland for domestic wastewater treatment in frigid climate presents special challenges. A full-scale wastewater treatment plant which utilized a novel greenhouse-structured, horizontal subsurface flow constructed wetland (HFCW) with bio-contact oxidation (BCO) pre-treatment was developed for sewage treatment. Reclaimed water was reused for irrigation in the rural area, northeast of China. The performance of the system showed that the annual average concentrations of COD, ammonia nitrogen (NH3N), and total phosphorus (TP) in final effluent were about 22.40 (±6.84), 8.58 (±1.48) and 2.09 (±0.28) mg/L, respectively. The insulation provided by the greenhouse, allowed the wetland and biological pre-treatment to overcome the disadvantage only using subsurface wetland and improve the pollutants removal efficiency in winter. Ornamental plants were planted in the constructed wetland, which provided economic benefits through selling them. The greenhouse provided a place for local people to communicate and entertain in winter, which raised the environmental awareness of local farmers. Probability analysis revealed that the BCO–HFCW combined system may be an alternative choice for many developing countries especially in frigid zones with temperature below 0 °C.