SBR System Research Articles

Enhanced refractory organics removal by sponge iron-coupled microbe technology: performance and underlying mechanism analysis.

Sponge iron (SFe) is a zero-valent iron (Fe0) composite with a high-purity and porous structure. In this study, SFe was coupled with microorganisms that were gradually domesticated to form a Fe0/iron-oxidizing bacteria system (Fe0-FeOB system). The enhancement effect of the Fe0-FeOB system on refractory organics was verified, the mechanism of its strengthening action was investigated, and the relationship and influencing factors between the Fe0 and microorganisms were revealed. The average removal rates of the Fe0-FeOB system were 8.98%, 5.69%, and 40.67% higher than those of the SBR system for AF, AN, and NB wastewater treatment, respectively. With the addition of SFe, the microbial community structure was gradually enhanced with a large number of FeOB were detected. Moreover, the bacteria with strong iron corrosion and Fe(II) oxidation abilities plays a critical role in improving the Fenton-like effect. Interestingly, the variation trend of ⋅OH was fairly consistent with that of Fe(II). Thus, the main drivers of the Fenton-like effect are biological corrosion and metabolism. Consequently, microbial degradation and Fenton-like effect contributed to the degradation performance of the Fe0-FeOB system. Among them, the microbial degradation accounted for 96.09%, of which the biogenic Fenton effect accounted for 8.9%, and the microbial metabolic activity accounted for 87.19%. However, the augmentation of the Fe0-FeOB system was strongly dependent on SFe for the strengthening effect of microorganisms disappeared after leaving the SFe 35days.

Performances of coffee husk biochar addition in a lab-scale SBR system for treating low carbon/nitrogen ratio wastewater

Performances of coffee husk biochar addition in a lab-scale SBR system for treating low carbon/nitrogen ratio wastewater

Effect of Ozone Dosage on Sludge Settleability and Biological Nutrient Removal in SBR System

The effect of ozone dosage on sludge settleability and biological nutrient removal performance in a sequencing batch reactor was investigated by inoculating the bulking sludge with the SVI of 280 mL·g-1 from a wastewater treatment plant in winter. The filamentous mycelium was interrupted, and the SVI was decreased to 125 mL·g-1 after ozone dosage with a low concentration of 0.085 g·g-1(O3/MLSS) for 20 days, which indicated the disappearance of the sludge bulking. The performance of nitrification and phosphorus removal efficiency was not affected obviously. However, the sludge settleability deteriorated with a high dosage of ozone, and the phosphorus removal efficiency was decreased to around 60%. Further study showed that PS/PN had a positive correlation with SVI with the correlation coefficient of 0.9381, which can be used to characterize sludge settleability. A low ozone dosage not only interrupted the filamentous mycelium, but it also affected the content and composition of the EPS, which led to improved settleability.

Bioaugmentation Technology for Treatment of Toxic and Refractory Organic Waste Water Based on Artificial Intelligence.

With the development of modern chemical synthesis technology, toxic and harmful compounds increase sharply. In order to improve the removal efficiency of refractory organic matter in waste water, the method of adding powdered activated carbon (PAC) to the system for adsorption was adopted. Through the analysis of organic matter removal rule before and after waste water treatment, it can be found that PAC is easy to adsorb hydrophobic organic matter, while activated sludge is easy to remove hydrophilic and weakly hydrophobic neutral organic matter. Powdered activated carbon-activated sludge SBR system (PAC-AS) system is obviously superior to AS and PAC system in removing organic matter of hydrophilic and hydrophobic components, that is, biodegradation and PAC adsorption are additive. Compared with the control system, the Chemical Oxygen Demand (COD) removal rate of refractory substances increased by 8.36%, and PAC had a good adsorption effect on small molecular weight organic compounds, but with the increase of molecular weight of organic compounds, the adsorption effect of PAC gradually weakened, and it had no adsorption effect on macromolecular organic compounds. Based on the research of fuzzy control theory, an Agent control system for ozone oxidation process of industrial waste water based on Mobile Agent Server (MAS) theory was established, which was realized by fuzzy control method. The simulation results showed strong stability and verified the feasibility and adaptability of the distributed intelligent waste water treatment system based on MAS theory in the actual control process.

Post-Treatment of the Effluent from Anaerobic Digestion of the Leachate in Two-Stage SBR System Using Alternative Carbon Sources

Although anaerobic digestion (AD) enables biogas production and facilitates renewable electricity production, its effluent must be post-treated before discarding it into the environment. However, during AD designing, the post-treatment step is often overlooked. This paper presents the kinetics and efficiency of nitrogen removal from effluent after AD of leachate from the aerobic stabilization of the organic fraction of municipal solid waste. A two-stage SBR system was used. An ammonium oxidation rate of 15.5 mg N-NH4/(L·h) ensured a 98% nitrification efficiency (I stage). For denitrification (II stage), alternative carbon sources (ACS) (molasses, crude glycerine, or distillery stillage) were used. Two volumetric exchange rates (n) were tested: 0.35 1/d (COD/N-NO3 ratio of 8) and 0.5 1/d (COD/N-NO3 of 7). With all ACS and COD/N-NO3 ratios, almost 100% of nitrate was denitrified; at the COD/N-NO3 of 8, biodegradable organics remained in the effluents. At the COD/N-NO3 of 7, the denitrification removal rates were lower (29.6-45.1 mg N-NOx/(L·h)) than at the ratio of 8 (72.1–159.5 mg N-NOx/(L·h)), because of temporal nitrite accumulation. The highest nitrate removal rates were obtained with molasses, the lowest with a distillery stillage. Considering the nitrate removal rate and the effluent COD concentration, molasses was recommended as the most effective carbon source for AD effluent treatment at the COD/N-NO3 of 7.

In-situ Sludge Reduction Technology Based on Ozonation

The process parameters and sludge properties of an in-situ sludge ozone-reduction system were investigated under different ozone dosages and sludge ages. Subsequently, 75 mg·g-1 (as O3/MLVSS) was selected as the appropriate ozone dosage to satisfy the wastewater treatment capacity and in-situ sludge ozone-reduction. The calibration coefficient results of the sludge yield formula indicated that Yh was reduced from 0.331 g·g-1 to 0.326 g·g-1 (to MLVSS/COD m) by ozone treatment and Kd was increased from 0.046 d-1 to 0.050 d-1 at 75 mg·g-1. The effluent quality of the SBR system was satisfactory when the sludge age was 10 d. The ozone dosage of 75 mg·g-1 and sludge age of 10 d were selected as the appropriate process conditions, at which the excess sludge was reduced by 12%. The high-throughput sequencing results concluded that the microorganisms in the excess sludge after ozonation were different in phylum and genus. After ozone treatment, the abundance of Bacteroidetes increased by 1.2 times and the relative abundance of Proteobacteria with nitrification and denitrification ability decreased from 24% to 18%. The reduction in the abundance of nitrobacteria affected the denitrification capacity of the sewage treatment system, but the total effluent nitrogen still met the I B discharge standard of pollutants for municipal wastewater treatment plants. The relative abundance of Lactococcus increased from 0.4% to 21.6%. Simultaneously, the concentration of macromolecular organic substances in the EPS of the excess sludge increased from 40.6 mg·g-1 to 54.6 mg·g-1, while the CST increased from 15 s to 17 s after ozone treatment. The zeta potential decreased from -10.04 mV to -15.20 mV and the SVI of the excess sludge increased from 54 mL·g-1 to 62 mL·g-1, thereby indicating that the sedimentation performance and dewaterability were affected to some extent. However, the SS of the effluent and the solids content of the sludge cake after extraction did not change significantly, the system could still operate stably, and the subsequent dewaterability of the excess sludge was not significantly affected.

Effects of different carbon sources on the removal of ciprofloxacin and pollutants by activated sludge: Mechanism and biodegradation

This research investigated the effects of ciprofloxacin (CIP) (0.5, 5, and 20 mg/L) on SBR systems under different carbon source conditions. Microbial community abundance and structure were determined by quantitative PCR and high-throughput sequencing, respectively. The biodegradation production of CIP and possible degradation mechanism were also studied. Results showed that CIP had adverse effects on the nutrient removal from wastewater. Compared with sodium acetate, glucose could be more effectively used by microorganisms, thus eliminating the negative effects of CIP. Glucose stimulated the microbial abundance and increased the removal rate of CIP by 18%–24%. The mechanism research indicated that Proteobacteria and Acidobacteria had a high tolerance for CIP. With sodium acetate as a carbon source, the abundance of nitrite-oxidizing bacterial communities decreased under CIP, resulting in the accumulation of nitrite and nitrate. Rhodanobacter and Microbacterium played a major role in nitrification and denitrification when using sodium acetate and glucose as carbon sources. Dyella and Microbacterium played positive roles in the degradation process of CIP and eliminated the negative effect of CIP on SBR, which was consistent with the improved removal efficiency of pollutants.

Optimization of aeration time on GAS-SBR system to remove organic content in wastewater

In general, chicken slaughterhouses have slaughtering capacity of more than 40,000 chickens per day, resulting in high volume wastewater with high BOD and COD concentration. Therefore, appropriate wastewater treatment technology is needed. Granular Activated Sludge that uses Sequencing Batch Reactor (GAS-SBR) has ability to treat wastewater with high organic content. The study is conducted to analyze the ability of GAS to reduce organic content with variation of aeration time in reaction stage on SBR. Formation of Granular Activated Sludge (GAS) was cultured by reacting activated sludge and using a stirring of 20 rpm. SBR had a total work volume of 45 liters and was operated in 5 stages, namely the filling, the reaction with aeration, the settling, the decantation, and the stabilization stage. In this study the initial COD concentration in chicken slaughterhouse effluent (RPA) was 5440 mg/L. The result of the study was that highest removal of BOD and COD parameter occured at 3 hours’ aeration time with removal efficiency 75% and 72%, while for TSS was at 5 hours’ aeration time with removal efficiency 65%. It could be concluded that GAS in SBR system could be applied to remove high organic content parameters in wastewater.

Effect of Fe3O4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Increasing magnetic Fe3O4 nanoparticles (Fe3O4 NPs) application has aroused concern about its potential environmental toxicity. During acute and chronic exposure, key enzymes involved in phenol biodegradation were promoted at 0–600 mg/L Fe3O4 NPs, while were inhibited at 800 mg/L Fe3O4 NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe3O4 NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe3O4 NPs concentration. At the same Fe3O4 NPs concentration, the removal of EPS further inhibited key enzymes, decreased phenol degradation, and increased LDH, indicating that the existence of EPS relieved the adverse effects on microorganisms. Spectroscopic analysis showed that protein and polysaccharide associated bonds in EPS decreased at 0–600 mg/L Fe3O4 NPs, while increased when Fe3O4 NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0–600 mg/L Fe3O4 NPs, while decreased at Fe3O4 NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.

A STUDY ON COMBINATION OF BIOCHAR AND ACTIVATED SLUDGE FOR REMOVING AMMONIUM FROM LOW C/N RATIO WASTEWATER

Grey domestic wastewater from septic tank contains high nitrogen content and low C/N ratio. Therefore, the aerobic biological treatment is often not effective for ammonium and nitrogen removal. The aim of this work was to study the performance of nitrogen removal and production of aerobic granular sludge using biochar produced from coffee husk pyrolyzed at 350oC as biocarrier. It was performed under the lab-scale SBR systems. Low C/N ratio domestic wastewater was used for this work. Coffee husk biochar (CFH 350) was added into the systems at different dosage. As a result, the biochar made from coffee husk pyrolyzed at low temperature promoted the adhesion of sludge onto biochar surface. The particles size of biochar played an important role for adsorption and adhesion capacity of activated sludge on biochar. The growth rate of bacterial sludge was accelerated and higher than control sample when biochar was used with biochar dose of 15 g/L. Though nitrification rate was improved as the bacterial sludge was accelerated, however, at initial stage, the removal efficiency of COD and total nitrogen was not as high as compare to traditional activated aerobic sludge system.

Removal of High Levels of Cyanide and COD from Cassava Industrial Wastewater by a Fixed-Film Sequencing Batch Reactor

The fixed-film sequencing batch reactor, or F-SBR, was developed to treat high organic compound levels and toxic cyanide concentrations in cassava wastewater. The performance of the F-SBR was compared with that of a conventional sequencing batch reactor, or SBR, that was operated with organic compound contents of 16,266.67–26,666 mg COD/L and 132.92–252.66 mg CN−/L. The cyanide and chemical oxygen demand removal efficiencies of the conventional SBR system were 42.61% and 36.83%, respectively, while those of the F-SBR were 77.95% and 74.43%, respectively; the cyanide removal efficiency reached 95.45% when the hydraulic retention time was increased to 5 days, and the F-SBR was very effective for the complete removal of cyanide when the hydraulic retention time was increased to 10 days. This effectiveness was similar to the effectiveness of chemical oxygen demand removal, which reached 40–78% efficiency with the F-SBR system. These results showed that the immobilization of cyanide-degrading bacteria such as Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2 carried out with a polypropylene ring in a fixed-film aerobic system enhanced the performance of the reactor and can be successfully applied for cyanide and chemical oxygen demand removal from industrial wastewater with high cyanide and chemical oxygen demand concentrations. This study may provide a promising alternative technique that reduces economic operation costs in solving wastewater contamination problems.

Recent developments in textile wastewater biotreatment: dye metabolite fate, aerobic granular sludge systems and engineered nanoparticles

Textile wastewater (TWW) represents a major source of pollution worldwide, carrying high organic loads, recalcitrant azo dyes and engineered nanoparticles (ENP), namely silver nanoparticles (AgNP). The development of cost-efficient, environmentally-friendly TWW treatment solutions is critical. Despite the successful biodecolorization of azo dyes under anaerobic conditions, clear evidence for subsequent aerobic biodegradation of the often toxic breakdown sulfonated aromatic amines is scarce. Moreover, the debatable AgNP toxicity mechanisms, and apparent AgNP retention in activated sludge have raised concerns regarding eventual negative impacts on wastewater treatment efficiency. The aerobic granular sludge (AGS) technology, which has recently been scaled-up and implemented for the treatment of domestic wastewater and some industrial wastewaters, seems highly promising for TWW treatment, due to the high biomass retention capacity, anaerobic/anoxic/aerobic microenvironments within granules and enhanced tolerance towards high organic loads and toxic compounds. A review of the existing literature on AGS application to TWW treatment is presented, with a focus on the removal of azo dyes and their metabolites and ENP. The applicability of AGS to dye-containing synthetic and real TWW has been tested in different SBR systems. Their hydrodynamic regimens and operational conditions have been optimized, namely regarding granulation, long-term stability, azo dye decolorization and biodegradation of aromatic amines. Although promising results have been published regarding AGS resistance towards ENP (particularly AgNP), their long-term effects on the physical stability, biochemical properties and microbial community of AGS deserve more investigation. Overall, this review provides relevant support for the application of AGS SBRs in TWW treatment as a potential sustainable alternative to avoid the pollution of natural water bodies with synthetic dyes and ENP.

Evaluation of methylparaben removal and microbial behavior using a SBR system

We evaluated the variation in microbial populations and the behavior of an SBR system in the removal of methylparaben (MePB). The experimentation was carried out for 14 weeks, in three operational stages as follows: stabilization (Stage I), (Stage II = 300 μgMePB/L and Stage III = 600 μgMePB/L). The variation of the microorganisms was analyzed over the experimentation time along with the contact with the pollutant to be degraded, and the removal percentage of COD and MePB, with results of 88±5,5% and 92±7,7% respectively. Kinetic of MePB removal was evaluated to obtain the rate constant of biological degradation, Kbiol. Using these kinetic results, the effect of different concentrations of MePB and biomass on biodegradation behavior was evaluated. Kbiol (LgSS-1d-1) values were obtained of 42.8 and 79 respectively; and 472±38.0 µgMePB/L, at biomass contents of 1466.7 and 2666.7 mgSSV/L, where Kbiol (LgSS-1d-1) values were obtained of 11.0 and 32.6 respectively.The variation of the microbial populations were analyzed using DGGE. The results obtained indicated that the populations presented similar characteristics between the stages. However, for the biomass samples of Stage I and stage III, significant differences were identified in the composition of microbial populations. Nonetheless, this did not affect the removal of MePB and the diversity conditions that characterize an aerobic system.

Effects of Long-term Poly-P Deficiency on the Metabolic Properties of Accumulibacter in AO-SBR System

To investigate the changes in microbial community structure and metabolic properties of Accumulibacter under long-term Poly-P deficiency, an activated sludge enriched with Accumulibacter was inoculated into two SBR reactors, where sodium acetate and sodium propionate were used separately as organic carbon sources. The two reactors were operated for 60 days with an influent PO43--P concentration of 2.5 mg·L-1. The phosphorus removal performance, sludge production, and changes in the microbial community structure of the systems were analyzed. The results indicated that both SBR systems showed good performance of phosphorus and organic matter removal. However, microorganisms in both systems showed glycogen-accumulating metabolism properties under long-term Poly-P deficiency. In the unfavorable environment of long-term Poly-P deficiency, Accumulibacter Ⅰ maintained a high abundance (40%±7%) in the propionate SBR system, indicating that Accumulibacter Ⅰ had higher metabolic activity and its metabolic properties could be independent of Poly-P for survival under Poly-P deficiency for a long period. In comparison, propionate is more conducive to Accumulibacter adaptation to lower phosphorus loads, and Accumulibacter Ⅰ is more competitive than Accumulibacter Ⅱ under lower phosphorus loads.

Nitrite effect on the phosphorus uptake activity of phosphate accumulating organisms (PAOs) in pilot-scale SBR and MBR reactors

Batch tests were performed to investigate the nitrite effect on the P-uptake of biomass grown in pilot-scale SBR and MBR systems. The results showed that the nitrite has an inhibitory effect on the aerobic P-uptake of the SBR and the MBR biomasses. The degree of inhibition was observed to be 65 % and 37 % at 10 mg NO2-N/l for the SBR and the MBR respectively. Both biomasses were found capable of using nitrite as electron acceptor as effectively as nitrate. Moreover, for the SBR biomass the anoxic P-uptake rate using nitrite was found even higher (60%) than the P-uptake rate with nitrate. From a modelling point of view, the current models require appropriate extensions to describe these various effects of nitrite. Hence, an extension of the ASM2d model has been provided. Prevention of nitrite build-up in full-scale EBPRs will eliminate the nitrite inhibition problem. Alternatively one can adopt a proactive approach in which the aerobic P-uptake phase is replaced with an anoxic P-uptake phase using only nitrite as electron acceptor. Such an approach offers considerable cost savings and enhanced nitrogen and phosphorus removal. This, however, requires further research for experimental validation and testing.

Anammox start-up strategies: the use of local mixed activated sludge seed versus Anammox seed

The start-up period of Anammox systems is still a big challenge due to the unavailability of large volumes of slowly growing Anammox seed locally in most countries. This study aims to evaluate the effects of seeding strategy on the start-up and enrichment period of Anammox systems by monitoring both process performance and microbial population dynamics. Two different seeding strategies, the use of mixed activated sludge culture from a local STP and the use of enriched Anammox culture transported from abroad, were comparatively studied in SBR systems operated for 410 days. The enriched Anammox seed from abroad inhibited seriously during transportation. Anammox activity re-started after 195 days' recovery period. An active Anammox culture was successfully enriched within 95 days from a local activated sludge source without seeding any Anammox. The Anammox population reached levels of 1011 copies/ng at the end of 410 days' enrichment period. Based on FISH, Ca. Brocadia anammoxidans and Ca. Scalindua species were dominant in the enriched culture. The maximum TNRR was observed as 430 mg N/day. DGGE analyses revealed a drastic change in the microbial community (56%) with Anammox enrichment. Phylogenetic analysis demonstrated a significant decrease in phylotype Proteobacteria and increase in phylotypes Planctomycetes, Chloroflexi and Acidobacteria with enrichment.

The role of the operating parameters of SBR systems on the SMP production and on membrane fouling reduction

In this work, six identical laboratory SBRs treating simulated wastewater were operated in parallel studying the effect of three food-to-microorganisms ratio (F/M ratio; 0.20, 0.35 and 0.50 kg COD·kg MLSS−1·d−1), two hydraulic retention times (HRT; 24 and 16 h) and two values of number of cycles per day (3 and 6). Influence of these operational parameters on the SMPs production and reactor performance, were studied. Results indicated that the highest F/M ratio, HRT and cycles/day produced 72.7% more of SMP. In a second experimental series, biological process yielding the maximal and the minimal SMPs production were replicated and both mixed liquors (ML) and treated effluents were ultrafiltrated. The flux decay in the conditions of minimum and maximum SMPs production were 52% and 72%, when the SBRs effluents were ultrafiltrated while no significant differences in the ultrafiltration of ML were found. In terms of permeability recovery, this was lower for the case of the ML (73% and 49% of initial permeability recovered for effluent and ML ultrafiltration, respectively).

2-Chlorophenol consumption by cometabolism in nitrifying SBR reactors

Cometabolic consumption of 2-chlorophenol (2-CP) by a nitrifying sludge was evaluated in two SBR reactors fed with 60 mg 2-CP-C/L and different initial ammonium concentrations (100, 200, 300, 400, and 500 mg NH4+-N/L). Irrespectively to the increase in ammonium concentration and throughout the operational cycles, the sludge achieved a complete nitrification in 14 days, accounting for ammonium consumption efficiencies close to 99% and nitrate production yields between 0.93 and 0.99. The sludge was able to completely consume 2-CP within 7 days. The increase in ammonium concentration provoked an increment in the specific rates of both ammonium (qNH4+-N) and 2-CP (q2-CP-C) consumption up to 5.2 and 3.1 times, respectively. The cometabolic effect of the increase in ammonium concentration on 2-CP consumption was supported by a direct and significant relationship between the qNH4+-N and q2-CP-C (r = 0.83). Moreover, batch assays conducted with ammonium, 2-CP, allylthiourea as specific inhibitor of the ammonium monooxygenase (AMO) enzyme, and the sludge inoculated into the reactors, resulted in a decrease of 34% in q2-CP-C, evidencing the participation of the AMO in the consumption of 2-CP. When the same assays were carried out with the sludge obtained from the SBR reactors after 13 operating cycles, a higher participation of the AMO in 2-CP consumption was noticed with a decrease of 53% in q2-CP-C. According to these results, the use of nitrifying sludge and high ammonium concentrations in SBR systems can be a suitable alternative for increasing the cometabolic consumption of recalcitrant compounds like 2-CP.

English

English

A pilot-scale study on start-up and stable operation of mainstream partial nitrification-anammox biofilter process based on online pH-DO linkage control

A pilot-scale study on start-up and stable operation of mainstream partial nitrification-anammox biofilter (PN/AF) system was conducted. The partial nitrification system was controlled based on online pH-dissolved oxygen (DO) linkage control strategy for nitrite oxidizing bacteria (NOB) out-selection. The immobilized anammox system was an upload biofilter reactor where anammox bacteria were immobilized on the volcanic carriers. The results showed that the nitrite accumulation ratio (NAR) was maintained above 90%, and the NO2—N/NH4+-N value was kept at 0.96 ± 0.18 in the effluent of the partial nitrification system; the mean ammonia concentration of the effluent was below 5 mg/L, and total inorganic nitrogen (TIN) removal loading could achieve 0.11 kg/m3·d after the stable operation in the whole system. The results of high-throughout sequencing showed that the NOB (mainly Nitrospira, Nitrotoga) was out of the partial nitrification system after 30-day operation, the relative abundance of which is less than 1% observed from Krona maps, and ammonia oxidizing bacteria (AOB, mainly Nitrosomonas) became the dominant species of nitrobacteria, the 8% of AOB stabilized finally. Dominant anammox bacteria was identified as genus Candidatus Brocadia, and one kind of rare anammox named Asahi BRW_2 was found to be at the downside of the volcanic biofilter reactor. It could be found the online pH-DO linkage control strategy allowed out-selection of NOB from the mainstream SBR system, and realized a stable partial nitrification. In addition, high DO (2.5 ± 0.5 mg/L) condition was found to be favorable for NOB out-selection and the stabilization of nitritation. The anammox bacteria could be well immobilized in volcanic carriers, with an ability of low ammonia resistance. The study was helpful for engineering application of mainstream anammox process.