Bio-entrapped membrane reactor and salt marsh sediment membrane bioreactor for the treatment of pharmaceutical wastewater: treatment performance and microbial communities

Novel intertidal wetland sediment-inoculated moving bed biofilm reactor treating high-salinity wastewater: Metagenomic sequencing revealing key functional microorganisms

In this study, two lab-scale moving bed biofilm reactors (MBBR), seeded with intertidal wetland sediment (IWS) and activated sludge (AS), were constructed to compare their performances in treating high-salinity (3%) wastewater. Under a wide range of influent TOC (178-620 mg/L) and NH₄⁺-N (25-100 mg/L), both the MBBRs (R_iws and R_as) exhibited excellent TOC removal efficiencies of >95%. Regarding nitrogen reduction, R_iws exhibited a significantly superior TN removal efficiency of 90.2 ± 1.8% than that of R_as (76.8 ± 2.9%). A correlation analysis was innovatively conducted comparing the results between metagenomic sequencing and DNA pyrosequencing, and positive linear relationships were found with R² values of 0.763-0.945. Meanwhile, for illustration of different TN removal performance, nitrogen metabolic pathways were also assessed. Moreover, a list of functional oxidases (EC: 1.13.11.1, EC: 1.13.11.2, EC: 1.13.11.24, EC: 1.13.12.16, EC: 1.4.3.4, EC: 1.16.3.3, EC: 1.14.14.28) was found in IWS, revealing its potential in degradation of recalcitrant organics.

Biotreatment efficiency, hydrolytic potential and bacterial community dynamics in an immobilized cell bioreactor treating caper processing wastewater under highly saline conditions

Although caper processing wastewaters (CPW) are characterized by high organic content and salt concentration, no attempt has been made to treat these effluents. In this study, an immobilized cell bioreactor efficiently treated CPW even at hypersaline conditions (100 g/L salinity). Nitrogen was mainly assimilated during biotreatment, as nitrification was inhibited at elevated salinities. The hydrolytic potential was assessed by determining glucanase, xylanase, glucosidase, lipase and protease activities, which were negatively affected above 20 g/L salinity as the consequence of the inhibition of non-halotolerant microbiota. Succession of non-halotolerant taxa by the slightly halotolerant bacteria Defluviimonas, Amaricoccus, Arenibacter, Formosa and Muricauda, and then by the moderately/extremely halotolerant genera Halomonas, Roseovarius and Idiomarina occurred over salinity increase. Diversity indices were reduced during transition from moderately saline to hypersaline conditions. A distinct network was formed at hypersaline conditions, consisting of the halotolerant genera Halomonas, Idiomarina, Saliterribacillus and Gracilibacillus.

Microbial community succession and its correlation with reactor performance in a sponge membrane bioreactor coupled with fiber-bundle anoxic bio-filter for treating saline mariculture wastewater

The application of MBR in high saline wastewater treatment is mainly constrained by poor nitrogen removal and severe membrane fouling caused by high salinity stress. A novel carriers-enhanced MBR system was successfully developed for treating saline mariculture wastewater, which showed efficient TN removal (93.2%) and fouling control. High-throughput sequencing revealed the enhancement mechanism of bio-carriers under high saline condition. Bio-carriers substantially improved the community structure, representatively, nitrifiers abundance (Nitrosomonas, Nitrospira) increased from 2.18% to 9.57%, abundance of denitrifiers (Sulfurimonas, Thermogutta, etc.) also rose from 3.81% to 14.82%. Thereby, the nitrogen removal process was enhanced. Noteworthy, ammonia oxidizer (Nitrosomonas, 8.26%) was the absolute dominant nitrifiers compared with nitrite oxidizer (Nitrospira, 1.13%). This supported the finding of shortcut nitrification-denitrification process in hybrid system. Moreover, a series of biomacromolecule degraders (Lutibacterium, Cycloclasticus, etc.) were detected in bio-carriers, which could account for the mitigation of membrane fouling as result of EPS and SMP degradation.

Effect of hydraulic retention time on pollutants removal from real ship sewage treatment via a pilot-scale air-lift multilevel circulation membrane bioreactor

Developing a real ship sewage treatment system that not only satisfies the requirement of small space onboard but also meets the latest emission standards of International Maritime Organization (IMO) is still a challenging task for ship industry. To overcome these problems, in this study, a novel pilot-scale air-lift multilevel circulation membrane bioreactor (AMCMBR) was used to explore the effect of hydraulic retention time (HRT) on effluent chemical oxygen demand (COD) and total nitrogen (TN) while treating real ship sewage. Results indicated that the satisfactory removal efficiencies of COD and TN was achieved in the former stages (Re(COD) = 91.57% and 87.82%; Re(TN) = 77.17% and 81.19%). When HRT decreased to 4 h, the removal efficiencies of COD and TN was 86.93% and 70.49% respectively, which still met the strict IMO discharge standards. This mainly because the biofilm-assistant membrane filtration lead to the increase of physical removal rate. The high ratio of mixed liquor volatile suspended solids (MLVSS)/mixed liquid suspended solids (MLSS) (i.e. 0.75) indicated a high biomass content in the attached sludge and resulted into perfect pollutants removal effort. The compliance rate of COD and TN was 100% and 89%, respectively, which indicated stable operation of the pilot-scale AMCMBR throughout the whole experiment. Fluorescence in situ Hybridization (FISH) analysis revealed that the abundance of β-Proteobacteria was a key microbial reason for TN removal. In addition, wavelet neural network (WNN) model was proved to be suitable to simulate and predict the COD and TN removal. These conclusions indicated that the pilot-scale AMCMBR technology is an effective way for real ship sewage treatment.

Entrapped biomass for removal of organics and total nitrogen from anaerobic reactor effluents

Anaerobic processes have been applied to treat low-strength domestic wastewaters with significant energy saving. However, anaerobic process effluents must be further removed of residual organics and total nitrogen before discharge. Reported here are an aerobic entrapped bio-technology (EBT) system and an EBT coupled with activated sludge (EBT + AS) system being tested as a post-anaerobic treatment. Both systems have been operated under aerobic condition to provide organics and total nitrogen removal, achieving COD removal by 74-88% and TN removal by 58-65% at hydraulic retention times of 8-24 h. ΔCOD/ΔNO₃ ratios that represent the carbon usage efficiency as electron donors for denitrification were 1.82-1.93 in the EBT and 2.01-2.02 in the EBT + AS systems, with both ratios being lower (i.e. more efficient) than 6 typically required in traditional activated sludge bioreactors. Both systems demonstrate promise for polishing removal of COD and TN.

Fate of pharmaceuticals during membrane bioreactor treatment: Status and perspectives

Pharmaceuticals in surface waters and wastewater treatment plants (WWTPs) as emerging pollutants have become a major concern. In comparison with other wastewater treatments, removal of pharmaceuticals in MBR has received much attention. This review presents the source and occurrence of pharmaceuticals in WWTPs influents. Experimental studies related to the removal of pharmaceuticals during MBR treatment, key affecting factors (including the different stages of MBR process configuration and the process parameters), and the underlying mechanisms proposed to explain the biodegradation and adsorption behaviors, have been comprehensively discussed. Several transformation products of pharmaceuticals are also reviewed in this paper. Furthermore, further research is needed to gain more information about the multiple influence factors of the pharmaceuticals elimination, appropriate methods for promoting pharmaceuticals elimination, more essential removal pathways, effect of pharmaceuticals on membrane fouling, and the detection and analysis of transformation products.

Effect of organic loading rate on the removal of DMF, MC and IPA by a pilot-scale AnMBR for treating chemical synthesis-based antibiotic solvent wastewater

This study focuses on the effects of organic loading rate (OLR) on the removal of N,N-Dimethylformamide(DMF), m-Cresol (MC) and isopropyl alcohol (IPA) by a pilot-scale anaerobic membrane bioreactor (AnMBR) for treating chemical synthesis-based antibiotic solvent wastewater at period of improved influent COD concentration with decreased HRT. The whole process was divided into five stages in terms of the variation of OLR ranging from 3.9 to 12.7 kg COD/(m³·d). During 249 days of operating time, the average DMF, MC, IPA removal efficiency were 96.9%,98.2% and 96.4%, respectively. Cake layer was accumulated on the membrane surface acted as a dynamic secondary biofilm which lead to the increase of physical removal rate. In addition, mathematical statistical models was built on the linear regression techniques for exploring the inner relationship between EPS and the performance of the AnMBR.

Performance and extracellular polymers substance analysis of a pilot scale anaerobic membrane bioreactor for treating tetrahydrofuran pharmaceutical wastewater at different HRTs

Tetrahydrofuran (THF) is one of the most representative characteristics of pollutant in pharmaceutical industry usually has high biological toxicity, making it difficult to treat. In this study, a pilot scale anaerobic membrane bioreactor (AnMBR) was employed to treat THF pharmaceutical wastewater under different hydraulic retention time (HRT). During the 80-day operating time, chemical oxygen demand (COD) and THF removal efficiencies reached 95.3% and 98.5% when HRT was above 24h. Mixed liquid suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) in the attached sludge on membrane surface showed a trend of rising on first 28days (48h-36h) and then decreasing. Protein is the major component of extracellular polymeric substances (EPS) independent of changes in HRT. The study concludes that THF pharmaceutical wastewater can be effectively remedied in the AnMBR system at low HRT.

Effects of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor for municipal wastewater treatment

This study aimed to evaluate the impact of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor (SAAMB-AnGMBR) in municipal wastewater treatment. The results showed that organic removal efficiencies were above 94% at all C/N conditions. Nutrient removal was over 91% at C/N ratio of 100/5 but was negatively affected when decreasing C/N ratio to 100/10. At lower C/N ratio (100/10), more noticeable membrane fouling was caused by aggravated cake formation and pore clogging, and accumulation of extracellular polymeric substances (EPS) in the mixed liquor and sludge cake as a result of deteriorated granular quality. Foulant analysis suggested significant difference existed in the foulant organic compositions under different C/N ratios, and humic substances were dominant when the fastest fouling rate was observed. The performance of the hybrid system was found to recover when gradually increasing C/N ratio from 100/10 to 100/5.

Effects of hydraulic retention time and bioflocculant addition on membrane fouling in a sponge-submerged membrane bioreactor

The characteristics of activated sludge and membrane fouling were evaluated in a sponge-submerged membrane bioreactor (SSMBR) at different hydraulic retention times (HRTs) (6.67, 5.33 and 4.00h). At shorter HRT, more obvious membrane fouling was caused by exacerbated cake layer formation and aggravated pore blocking. Activated sludge possessed more extracellular polymeric substances (EPS) due to excessive growth of biomass and lower protein to polysaccharide ratio in soluble microbial products (SMP). The cake layer resistance was aggravated by increased sludge viscosity together with the accumulated EPS and biopolymer clusters (BPC) on membrane surface. However, SMP showed marginal effect on membrane fouling when SSMBRs were operated at all HRTs. The SSMBR with Gemfloc® addition at the optimum HRT of 6.67h demonstrated superior sludge characteristics such as larger floc size, less SMP in mixed liquor with higher protein/polysaccharide ratio, less SMP and BPC in cake layer, thereby further preventing membrane fouling.

Nutrient capture and recycling by periphyton attached to modified agrowaste carriers

The reuse of periphytic biofilm from traditional wastewater treatment (i.e., active sludge process) is inefficient to recycle nutrients due to low accumulation of nutrients. Then, in this study, peanut shell (PS), rice husk (RH), decomposed peanut shell (DPS), acidified rice husks (ARH), and a commonly used carrier-ceramsite (C, as the control)-were used to support the growth of periphyton. Results showed that DPS and ARH supported significantly higher periphyton biomass and metabolic versatility than PS and RH, respectively, due to the increased presence of positive groups. The total nitrogen (TN) and total phosphorus (TP) captured by periphyton were enhanced by 600-657 and 833-3255 % for DPS, and 461-1808 and 21-308 % for ARH, respectively. The removal of nutrients from simulated eutrophic surface waters using periphyton attached to DPS was improved by 24-47 % for TP, 12-048 % for TN, and 15-78 % for nitrate compared to the control. The results indicate that the periphyton attached to modified agrowaste was capable of efficiently entrapping and storing N and P from eutrophic water. This study also implies that the mixture of periphyton and the modified agrowaste carriers are promising raw materials of biofertilizer.

Pyrosequencing reveals microbial community profile in anaerobic bio-entrapped membrane reactor for pharmaceutical wastewater treatment

In this study, pharmaceutical wastewater with high salinity and total chemical oxygen demand (TCOD) was treated by an anaerobic membrane bioreactor (AnMBR) and an anaerobic bio-entrapped membrane reactor (AnBEMR). The microbial populations and communities were analyzed using the 454 pyrosequencing method. The hydraulic retention time (HRT), membrane flux and mean cell residence time (MCRT) were controlled at 30.6h, 6L/m(2)h and 100d, respectively. The results showed that the AnBEMR achieved higher TCOD removal efficiency and greater biogas production compared to the AnMBR. Through DNA pyrosequencing analysis, both the anaerobic MBRs showed similar dominant groups of bacteria and archaea. However, phylum Elusimicrobia of bacteria was only detected in the AnBEMR; the higher abundance of dominant archaeal genus Methanimicrococcus found in the AnBEMR could play an important role in degradation of the major organic pollutant (i.e., trimethylamine) present in the pharmaceutical wastewater.

Assessing the feasibility of N and P recovery by struvite precipitation from nutrient-rich wastewater: a review

Literature on recovery of nitrogen and phosphorous from wastewater in the form of value-added struvite fertilizer has been critically reviewed towards the evolution of a sustainable management strategy. Presence of nitrogen and phosphorus is widespread in both domestic as well as industrial wastewater streams such as swine wastewater, landfill leachate, urine waste, dairy manure, coke wastewater, and beverage wastewater. Where these nitrogen and phosphorus compounds cause eutrophication of water bodies and considered as harmful discharges to the environment, they can be turned useful through simple chemical conversion into struvite (MgNH4PO4·6H2O). In extensive studies on wastewater treatment, aspects of recovery of valuable materials remain dispersed. In the present article, almost all relevant aspects of sources of raw materials, chemistry and technology of struvite production, and its detailed characterization have been captured in a systematic and classified way so as to help in planning and designing an integrated scheme of struvite production through conversion of nitrogen and phosphorus components of waste streams. The study will help in formulating a new waste management strategy in this context by shifting focus from removal to recovery of nutrients from waste streams.

Investigation of intertidal wetland sediment as a novel inoculation source for anaerobic saline wastewater treatment

Biological treatment of saline wastewater is considered unfavorable due to salinity inhibition on microbial activity. In this study, intertidal wetland sediment (IWS) collected from a high saline environment was investigated as a novel inoculation source for anaerobic treatment of saline pharmaceutical wastewater. Two parallel lab-scale anaerobic sequencing batch reactors (AnSBR) were set up to compare the organic removal potential of IWS with conventional anaerobic digested sludge (ADS). Under steady-state condition, IWS reactor (R(i)) showed organic reduction performance significantly superior to that of ADS reactor (R(a)), achieving COD removal efficiency of 71.4 ± 3.7 and 32.3 ± 6.1%, respectively. In addition, as revealed by fluorescent in situ hybridization (FISH) analysis, a higher relative abundance of methanogenic populations was detected in R(i). A further 16S rRNA gene pyrosequencing test was conducted to understand both the bacterial and archaeal community populations in the two AnSBRs. A predominance of halophilic/tolerant microorganisms (class Clostridia of bacteria, genera Methanosarcina, and Methanohalophilus of archaea) in R(i) enhanced its organic removal efficiency. Moreover, several microbial groups related with degradation of hardly biodegradable compounds (PAHs, n-alkenes, aliphatic hydrocarbons, and alkanes, etc.) were detected in the IWS. All these findings indicated that IWS is a promising inoculation source for anaerobic treatment of saline wastewater.

Comparative metagenomics demonstrating different degradative capacity of activated biomass treating hydrocarbon contaminated wastewater

This study demonstrates the diverse degradative capacity of activated biomass, when exposed to different levels of total dissolved solids (TDS) using a comparative metagenomics approach. The biomass was collected at two time points to examine seasonal variations. Four metagenomes were sequenced on Illumina Miseq platform and analysed using MG-RAST. STAMP tool was used to analyse statistically significant differences amongst different attributes of metagenomes. Metabolic pathways related to degradation of aromatics via the central and peripheral pathways were found to be dominant in low TDS metagenome, while pathways corresponding to central carbohydrate metabolism, nitrogen, organic acids were predominant in high TDS sample. Seasonal variation was seen to affect catabolic gene abundance as well as diversity of the microbial community. Degradation of model compounds using activated sludge demonstrated efficient utilisation of single aromatic ring compounds in both samples but cyclic compounds were not efficiently utilised by biomass exposed to high TDS.