Optimized operational parameters of a pilot scale membrane bioreactor for high-strength organic wastewater treatment

A pilot-scale test was conducted in a submerged membrane bioreactor (SMBR) for 452 days to treat high-strength traditional Chinese medicine wastewater from two-phase anaerobic digest effluent. This study focuses on the effects of operational parameters on effluent quality of a SMBR. The parameters include shorter hydraulic retention time (HRT), higher influent COD concentration, higher COD loading rate and mixed liquor suspended solids (MLSS). The experimental results demonstrated that when HRT was 5 h and the influent COD was less than 3000 mg L⁻¹, the effluent quality of the SMBR evaluated from its COD content (COD_filt) could meet the accepted Chinese standards for water reclamation; when HRT was 3.2 h and the influent COD was less than 3000 mg L ⁻¹, or HRT was 5 h and the influent COD fluctuated between 3000 and 6000 mg L⁻¹, the effluent quality of the SMBR could meet the normal Chinese discharged standard. Statistical analyses showed that COD_filt correlated positively with the COD loading rate. It correlated negatively with the MLSS for MLSS values between 7543 and 13 694 mg L⁻¹. When MLSS was >13 694 mg L⁻¹ it correlated positively with COD_filt. Based on experimental values from SMBR and on values predicted by a simulation model generated using the back propagation neural network (BPNN) theory, the optimum operational parameters for the treatment of a high-strength TCM wastewater were as follows: HRT was 5 h, SRT was 100 day, COD loading rate was<20.5 kg m⁻³ d⁻¹, the range of MLSS was 7543–13 694 mg L⁻¹.     

Study of operational conditions of simultaneous nitrification and denitrification in a Carrousel oxidation ditch for domestic wastewater treatment

The study on the operational conditions of simultaneous nitrification and denitrification (SND) in the channel of oxidation ditch (OD) without the need for a special anoxic tank was carried out based on lab-scale and pilot-scale experiments using real domestic wastewater. The influence of sludge loading and component proportion in influent, temperature, hydraulic retention time (HRT), dissolved oxygen (DO) and operational mode on SND was investigated. The result indicated that the optimal DO (ODO) of SND occurrence was confirmed majorly by the sludge loading of influent and temperature, the high TCOD/NH₃–N and short HRT can enhance the occurrence of SND. A new operational mode was proposed that achieved a higher removal efficiency of 60–70% for total nitrogen by SND with HRT of 4–6 h, and the concentrations of NH₃–N and TN in effluent are less than 5 and 15 mg/L, respectively.     

The influence of variable organic loading on the start-up of an anaerobic fluidised bed reactor

Summary A stepped-loading start-up regime utilising variable organic influent concentrations in the range 1650–11600 mgCOD1^–1 was applied to an anaerobic fluidised bed bioreactor at 37°C. The reactor was sensitive to variable influent COD concentrations, but the stepped-loading aided rapid recovery from transient organic loading shocks. Variable effluent COD levels were produced but a COD removal efficiency of 76% was obtained at a final HRT of 0.5 d and an organic loading rate of 5.3 kg COD m^–3 d^–1.     

The effect of pH on the efficiency of an SBR processing piggery wastewater

To treat piggery wastewater efficiently, the hydrolysis of urea (mainly derived from swine urine) in piggery wastewater with the change of sewage pH must be considered. Using activated sludge, piggery wastewater was treated in a sequencing batch reactor (SBR), and the effects of influent pH on SBR processing efficiency, sludge settle ability, and sludge activity were investigated. The results showed that a high influent pH value contributed to the improvement of the removal rate of ammonia nitrogen and reduction of the chemical oxygen demand (COD). When the influent pH was between 9.0 and 9.5, the removal rate of ammonia nitrogen was higher than 90%, and the reduction of COD from its original value was 80%. The influent pH had a greater influence on sludge concentration and sludge activity. When the influent pH increased from 7.0 to 9.5, the sludge concentration increased from 2,350 to 3,947 mg/L in the reactor, and the activities of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) first increased and then decreased. When the influent pH was 9.0 and 8.0, the maximum values (0.48 g O₂/(g MLSS/day) and 0.080 g O₂/(g MLSS/day)) were reached, and the sludge settling ratio was nearly steady between 20 and 35% in each reactor.     

Sequential kinetic parameter estimation of anaerobic fluidized bed bioreactor using an optimization technique

Mathematical model parameters for the methanogenic degradation of propylene glycol were estimated in a sequential manner by means of an optimization technique. Model parameters determined from an initial experimental data set using one bioreactor were then verified with the results from a second bioreactor. The proposed methodology is a useful tool to obtain model parameters for continuous flow reactors with completely mixed regime. Abbrevations: S – substrate concentration (mg COD l^–1); S _in – influent substrate concentration (mg COD l^–1); D _L – dilution rate (day^–1); – stoichiometric coefficients (ND); nx – number of microbial species (ND); X _S – fixed biomass concentration (mg biomass l^–1); X _L – suspended biomass concentration of (mg biomass l^–1); k _d – decay rate of biomass (day^–1); b _S – specific detachment rate of biofilm (day^–1); – specific growth rate of biomass (day^–1); _m – maximum specific growth rate of biomass (day^–1); K _S – half saturation constant (mg COD l^–1); K _I – inhibition constant (mg COD l^–1).     

Treatment of domestic wastewater in an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor

The performance of a laboratory-scale sewage treatment system composed of an up-flow anaerobic sludge blanket (UASB) reactor and a moving bed biofilm reactor (MBBR) at a temperature of (22–35 °C) was evaluated. The entire treatment system was operated at different hydraulic retention times (HRT’s) of 13.3, 10 and 5.0 h. An overall reduction of 80–86% for COD_total; 51–73% for COD_colloidal and 20–55% for COD_soluble was found at a total HRT of 5–10 h, respectively. By prolonging the HRT to 13.3 h, the removal efficiencies of COD_total, COD_colloidal and COD_soluble increased up to 92, 89 and 80%, respectively. However, the removal efficiency of COD_suspended in the combined system remained unaffected when increasing the total HRT from 5 to 10 h and from 10 to 13.3 h. This indicates that, the removal of COD_suspended was independent on the imposed HRT. Ammonia-nitrogen removal in MBBR treating UASB reactor effluent was significantly influenced by organic loading rate (OLR). 62% of ammonia was eliminated at OLR of 4.6 g COD m⁻² day⁻¹. The removal efficiency was decreased by a value of 34 and 43% at a higher OLR’s of 7.4 and 17.8 g COD m⁻² day⁻¹, respectively. The mean overall residual counts of faecal coliform in the final effluent were 8.9 × 10⁴ MPN per 100 ml at a HRT of 13.3 h, 4.9 × 10⁵ MPN per 100 ml at a HRT of 10 h and 9.4 × 10⁵ MPN per 100 ml at a HRT of 5.0 h, corresponding to overall log₁₀ reduction of 2.3, 1.4 and 0.7, respectively. The discharged sludge from UASB–MBBR exerts an excellent settling property. Moreover, the mean value of the net sludge yield was only 6% in UASB reactor and 7% in the MBBR of the total influent COD at a total HRT of 13.3 h. Accordingly, the use of the combined UASB–MBBR system for sewage treatment is recommended at a total HRT of 13.3 h.     

Nitrate removal from the effluent of a fertilizer industry using a bioreactor packed with immobilized cells of <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis>and<Emphasis Type="Italic">Comamonas testosteroni</Emphasis>

A bioreactor for the removal of nitrate nitrogen (NO₃-N) from industrial effluent is described which is comprised of a glass column (60 cm × 6 cm) packed with alginate beads containing denitrifying organisms Pseudomonas stutzeri and Comamonas testosteroni. The effluent containing high concentrations of nitrate (600–950 mg l^–1) from the fertilizer industry and fusel oil (methanol as a major component) as organic carbon were used in the process. The reactor is operated in the continuous mode by injecting the pretreated nitrate-containing effluent at the top of the column. The Hydraulic retention time (HRT) was adjusted by changing the flow rates. When nitrate-containing wastewater was treated with immobilized cells, the nitrate removal rate reached a maximum 1.66 ± 0.07 Kg NO₃-N m^–3d^–1 at an influent NO₃-N concentration of 850 mg NO_3M-N l^–1within 12 h. The denitrification activity of the immobilized cells was compared with that of the free cells.     

实验室模拟高负荷SPAC厌氧反应器运行

采用模拟废水, 对新型高负荷螺旋式自循环(Spiral automatic circulation, SPAC)厌氧反应器的运行性能进行了实验室模拟研究。结果表明: 在30oC, 水力停留时间(HRT)为12 h, 进水COD浓度从8000 mg/L升至20 000 mg/L的条件下, 反应器的COD去除率为91.1%~95.7%, 平均去除率为93.6％。在进水浓度为20 000 mg/L, HRT由5.95 h缩短至1.57 h的工况下, COD去除率从96.0%降低至78.7%, 反应器达到最高容积负荷率306 g COD/(L·d), 最大容积COD去除率240 g/(L·d), 最高容积产气率131 L/(L·d)。该反应器对基质浓度的连续提升具有良好的适应能力。进水COD浓度由8000 mg/L提升至20 000 mg/L时, 出水COD浓度一直处在较低水平(平均为852?mg/L), 容积COD去除率和容积产气率分别提高162%和119%。该反应器对HRT的连续缩短也有良好的适应能力。HRT由5.95 h缩短至1.57 h时,反应器容积COD去除率和容积产气率分别升高191%和195%。     

Simultaneous removal of chemical oxygen demand (COD), phosphate, nitrate and H2S in the synthetic sewage wastewater using porous ceramic immobilized photosynthetic bacteria

Simultaneous aerobic treatment of COD, phosphate, nitrate and H₂S in a synthetic sewage wastewater was carried out using porous ceramic immobilized photosynthetic bacteria, Rhodobacter sphaeroidesS, Rb. sphaeroidesNR-3 and Rhodopseudomonas palustris. In the batch treatment, effective simultaneous removal of COD (89%), phosphate (77%), nitrate (99%) and H₂S (99.8%) was observed after 48 h. In semi-continuous treatments with dilution rates of 0.17 to 0.75 day^–1under aerobic conditions, simultaneous removal of these four components was also observed after about one month.     

Cotton yarn and fabric finishing wastewater treatment in upflow anaerobic filter

Summary Wastewater from cotton yarn and fabric finishing was successfully treated in an upflow anaerobic filter at 35°C up to a COD loading of 1 Kgr COD/m³ · day; the COD removal varied from 50 to 90% and production of biogas was 0,2–0.4 L/g influent COD, having 70–80% CH₄. At higher COD loading biogas production stopped although COD removal remainedca 50%.     

Cotton fabric desizing and scouring wastewater treatment in upflow anaerobic filter

Summary Wastewater from textile desizing and scouring was successfully treated in an upflow anaerobic filter at 35°C; the COD loading waas gradually increased up to 2.75 kg/m³day with COD removal of 60–90%, and production of 0.2–0.5 L gas/g. influent COD, having 75–80% CH₄.     

Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process

A laboratory-scale anaerobic–anoxic/nitrification sequencing batch reactor (A₂N-SBR) fed with domestic wastewater was operated to examine the effect of varying ratios of influent COD/P, COD/TN and TN/P on the nutrient removal. With the increased COD/P, the phosphorus removals exhibited an upward trend. The influent TN/P ratios had a positive linear correlation with the phosphorus removal efficiencies, mainly because nitrates act as electron acceptors for the phosphorus uptake in the A₂N-SBR. Moreover, it was found that lower COD/TN ratio, e.g. 3.5, did not significantly weaken the phosphorus removal, though the nitrogen removal first decreased greatly. The optimal phosphorus and nitrogen removals of 94% and 91%, respectively were achieved with influent COD/P and COD/TN ratios of 19.9 and 9.9, respectively. Additionally, a real-time control strategy for A₂N-SBR can be undertaken based on some characteristic points of pH, redox potential (ORP) and dissolved oxygen (DO) profiles in order to obtain the optimum hydraulic retention time (HRT) and improve the operating reliability.     

Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter

In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O₃-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O₃-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7 h, 9.2 h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O₃-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O₃-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O₃-BAF combine process for textile wastewater treatment.     

Effects of glucose and phenol on soluble microbial products (SMP) in sequencing batch reactor systems

Soluble microbial products (SMP) are ubiquitously present in the effluents of biological wastewater treatment systems. In sequencing batch reactor (SBR) systems, effects of influent concentration and temperature on the amount and the molecular weight (MW) distribution of SMP were investigated for the two substrates, glucose and phenol. The values of effluent SMP/S₀ of phenol were higher than those of glucose at different influent concentrations and temperatures. It was found that the effluent SMP (S_e) was linearly correlated to the influent total organic carbon (TOC) (S₀) for both substrates. The slope and intercept of the equation were affected by the temperature. According to the analysis of the MW distribution, it was shown that there exists a bimodal pattern with the majority of SMP having a MW<1 kDa or >10 kDa. The low MW fraction (<1 kDa) amounts to 47.3–70.4% of the effluent SMP. The high MW fraction (>10 kDa) slightly fluctuates in the range of 21.2–32.8% of the effluent SMP.     

OLAND is feasible to treat sewage-like nitrogen concentrations at low hydraulic residence times

Energy-positive sewage treatment can, in principle, be obtained by maximizing energy recovery from concentrated organics and by minimizing energy consumption for concentration and residual nitrogen removal in the main stream. To test the feasibility of the latter, sewage-like nitrogen influent concentrations were treated with oxygen-limited autotrophic nitrification/denitrification (OLAND) in a lab-scale rotating biological contactor at 25°C. At influent ammonium concentrations of 66 and 29 mg N L⁻¹ and a volumetric loading rate of 840 mg N L⁻¹ day⁻¹ yielding hydraulic residence times (HRT) of 2.0 and 1.0 h, respectively, relatively high nitrogen removal rates of 444 and 383 mg N L⁻¹ day⁻¹ were obtained, respectively. At low nitrogen levels, adapted nitritation and anammox communities were established. The decrease in nitrogen removal was due to decreased anammox and increased nitratation, with Nitrospira representing 6% of the biofilm. The latter likely occurred given the absence of dissolved oxygen (DO) control, since decreasing the DO concentration from 1.4 to 1.2 mg O₂ L⁻¹ decreased nitratation by 35% and increased anammox by 32%. Provided a sufficient suppression of nitratation, this study showed the feasibility of OLAND to treat low nitrogen levels at low HRT, a prerequisite to energy-positive sewage treatment.     

Studies in nitrification of municipal sewage in an upflow biofilter

The upflow aerated biofilter with polyurethane foam cubes as the supporting medium was used for the investigation of nitrification studies on municipal sewage (secondary treated as well as untreated domestic sewage). In case of secondary treated sewage effluent, a synthetic composition of NH₄ ⁺-N and COD of each 50?mg/l was studied for a HRT variation of 24, 12, 8 and 6 hours. The ammonium removal efficiencies were found to be in the range of 98 to 100% with the steady-state effluent concentrations of NH₄ ⁺-N and NO₂ ^?-N in the range of 1–4 mg/l and 0.1–0.2?mg/l respectively. In case of domestic sewage system, nitrification studies along with suspended solids removal study was carried-out on untreated sewage for a HRT variation of 24, 12 and 6 hours. The ammonium removal efficiencies of 100% were observed for all the three HRT values at very high COD/NH₄ ⁺-N ratio of 15. The suspended solids removal efficiencies of 95 to 98% were observed with the average effluent suspended solids concentration of 5.9 to 15.9?mg/l. The experiments were conducted in non-backwash conditions of the biofilter. The study has revealed the best use of the upflow biofilter system for nitrification applications and suspended solids removal.     

Biodegradation performance of an anaerobic hybrid reactor treating olive mill effluent under various organic loading rates

The primary objective of this study was to evaluate the performance of a 20 l lab scale anaerobic hybrid reactor (AHR) combining sludge blanket in the lower part and filter in the upper part under varying organic loading rates (OLRs) in order to study biodegradation of olive mill effluent (OME). For this purpose, some parameters, such as total phenols, effluent chemical oxygen demand (COD), suspended solids (SS), volatile fatty acids (VFAs), and pH in the influent and effluent, and removal efficiencies for those parameters (except pH) were continuously monitored throughout the experimental period of 477 days. Eleven different organic loadings between 0.45 and 32 kg COD m⁻³ day⁻¹ were imposed by either varying influent COD or hydraulic retention time (HRT). The results demonstrated that the AHR reactor could tolerate high influent COD concentrations. Removal efficiencies for the studied pollution parameters were found to be as follows: COD, 50–94%; total phenol, 39–80%; color, 0–54%; and suspended solids, 19–87%. The levels of VFAs in the effluent, which was principally acetate, butyrate, iso-butyrate, and propionate, varied between 10 and 2005 mg l⁻¹ depending upon OLRs. A COD removal efficiency of 90% could be achieved as long as OLR is kept at a level of less than 10 kg COD m⁻³ day⁻¹. However, a secondary treatment unit for polishing purposes is necessary to comply with receiving media discharge standards.     

Influence of wastewater composition on nutrient removal behaviors in the new anaerobic–anoxic/nitrifying/induced crystallization process

In this study, the new anaerobic–anoxic/nitrifying/induced crystallization (A₂N–IC) system was compared with anaerobic-anoxic/nitrifying (A₂N) process to investigate nutrient removal performance under different influent COD and ammonia concentrations. Ammonia and COD removal rates were very stable in both processes, which were maintained at 84.9% and 86.6% when the influent ammonia varied from 30 mg L⁻¹ to 45 mg L⁻¹ and COD ranged from 250 mg L⁻¹ to 300 mg L⁻¹. The effluent phosphorus always maintained below 0.2 mg L⁻¹ in A₂N–IC, whereas in A₂N the effluent phosphorus concentration was 0.4–1.7 mg L⁻¹, demonstrating that A₂N–IC is suitable to apply in a broader influent COD and ammonia concentration range. Under higher influent COD (300 mg L⁻¹) or lower ammonia conditions (30 mg L⁻¹), the main function of chemical induced crystallization was to coordinate better nutrient ratio for anoxic phosphorus uptake, whereas under high phosphorus concentration, it was to reduce phosphorus loading for biological system. Under the similar influent wastewater compositions, phosphorus release amounts were always lower in A₂N–IC. To clarify the decrease procedure of phosphorus release in the A₂N–IC, the equilibrium between chemical phosphorus removal and biological phosphorus removal in A₂N–IC was analyzed by mass balance equations. During the long-term experiment, some undesirable phenomena were observed: the declining nitrification in post-aerobic tank and calcium phosphorus precipitation in the anaerobic tank. The reasons were analyzed; furthermore, the corresponding improvements were proposed. Nitrification effect could be enhanced in the post-aerobic tank, therefore ammonia removal rate could be increased; and biologically induced phosphorus precipitation could be inhibited by controlling pH at the anaerobic stage, so the phosphorus release and recovery could be improved.     

Simultaneous Carbon and Nitrogen Removal from Domestic Wastewater using High Rate Vermifilter

Being a cost-effective and environmentally benign technology, vermifiltration has significantly replaced the available conventional wastewater remediation methods in many cases over the last few decades. The present work emphasizes on the investigation of the nitrogen transformation dynamics, in addition to the organic carbon abatement in the designed high rate hybrid vermifilter. Moreover, the economical sustainability of the vermifiltration technology has also been enlightened by creating a bridge with the concept of circular bio-economy. The designed high rate macrophyte-assisted vermifilter (MAVF) ascertained significant high nitrogen and organic carbon removal efficiencies from the real domestic sewage, considering the chemical oxygen demand (COD) of the influent and hydraulic loading rate (HLR) as the input variables. The designed MAVF facilitated the maximum ammonium nitrogen (NH₄⁺-N), organic nitrogen, and total kjeldahl nitrogen removal efficiencies up to 98.2 ± 0.70%, 100%, and 99 ± 0.47%, respectively when COD of the influent and HLR were 200 ± 25 mg/L and 3 ± 0.1 m³/m²-d, respectively. On the other hand, substantial enhancement in the nitrate nitrogen (NO₃⁻-N) in the effluent (73 ± 10.55 times its influent concentration) was observed with influent COD of 200 ± 25 mg/L and HLR of 7 ± 0.2 m³/m²-d. When the influent COD and HLR were maintained at 700 ± 45 mg/L and 3 ± 0.1 m³/m²-d, respectively, the highest total nitrogen removal of 87 ± 2.25% was obtained. Alternatively, the influent COD of 200 ± 25 mg/L and HLR of 3 ± 0.1 m³/m²-d yielded the highest COD removal efficiency of 77 ± 1.59%. Hence, the outcome of the present research work strengthens the suitability of the vermifiltration technology as an economically and ecologically sound natural wastewater bio-remediation technology for the treatment of domestic wastewater.     

Removal of carbonaceous and nitrogenous pollutants from a synthetic wastewater using a membrane-coupled bioreactor

Two modified Ludzack-Ettinger (MLE)-type membrane-coupled bioreactors (MBRs) were investigated in this study for the purpose of removing both nitrogenous and carbonaceous pollutants from a synthetic wastewater. During the first MBR experiment, removal efficiencies were high (>90%) for chemical oxygen demand (COD) and ammonia, but total nitrogenous pollutant removal efficiency was poor (~25%). Bacterial community analysis of ammonia oxidizing bacteria (AOB) by a nested PCR-DGGE approach detected two Nitrosomonas-like populations and one Nitrosospira-like population. During the initial portion of the second MBR experiment, COD and ammonia removal efficiencies were similar to the first MBR experiment until the COD of the influent wastewater was increased to provide additional electron donors to support denitrification. Total nitrogen removal efficiencies eventually exceeded 90%, with a hydraulic residence time (HRT) of 24 h and a recirculation ratio of 8. When the HRT of the MBR experiment was decreased to 12 h, however, ammonia removal efficiency was adversely affected. A subsequent increase in the HRT to 18 h helped improve removal efficiencies for both ammonia (>85%) and total nitrogenous compounds (~70%). Our research demonstrates that MBRs can be effectively designed to remove both carbonaceous and nitrogenous pollutants. The ability of the microbial community to switch between anoxic (denitrifying) and oxic (nitrifying) conditions, however, represents a critical process constraint for the application of MLE-type MBR systems, such that little benefit is gained compared to conventional designs.