Biological COD reduction and inorganic suspended solids accumulation in a pilot-scale membrane bioreactor for traditional Chinese medicine wastewater treatment

A pilot-scale test was conducted in a membrane bioreactor (MBR) for 452 days to treat high-strength traditional Chinese medicine (TCM) wastewater from two-phase anaerobic digest effluent. This study focuses on the chemical oxygen demand (COD) reduction and inorganic suspended solid (ISS) accumulation. The wastewater was high in COD, varying daily between 259 and 12,776 mg L⁻¹. Almost all the COD was removed by the MBR system, leaving a COD of <50 mg L⁻¹ in the MBR effluent. This indicated a great potential of the MBR in TCM wastewater reuse. ISS produced in the bioreactor by metabolism of microorganism increased from 265 to 4912 g h⁻¹, which showed that there were large numbers of ISS accumulation in the bioreactor. Two models, built on the material balances of COD and ISS, were developed for the simulation of MBR system performance in the biodegradation of TCM wastewater. Consequently, the kinetic constants including the maximum substrate specific biodegradation rate (V_max), the half-saturation coefficient (K_s) and the inorganic suspended solids growth rate (k) were calculated as V_max, 3.64, 3.82, 4.39 d⁻¹, K_s, 56.4, 225, 394 mg L⁻¹ and k, 265, 888, 4912 mg L⁻¹ d⁻¹ using the operational data at different hydraulic retention times (HRTs). The models well fitted the pilot-scale experimental data, and were able to simulate the COD reduction and ISS accumulation.     

The effect of COD/N ratio on process performance and membrane fouling in a submerged bioreactor

Influent chemical oxygen demand/nitrogen (COD/N) ratio is used to control fouling in membrane bioreactor (MBR) systems. However, COD/N also affects the physicochemical and biological properties of MBR biomass. The current study examined the relationship between COD/N ratio in feed wastewater and extracellular polymeric substances (EPS) production in MBRs. Two identical submerged MBRs with different COD/N ratios of 10:1 and 5:1 were operated in parallel. The cation concentration and floc-size of the sludge were measured. The composition and characteristics of bound EPS and soluble microbial products (SMP) under each COD/N ratio were also examined. Batch tests were conducted in 1000 mL bottles to study the process of the release of foulants from the sludge when 1 g of (NH₄⁺-N)/L was added. Results showed that the influent COD/N ratio could change the physicochemical properties of EPS and SMP. Moreover, excessive NH₄⁺ in the supernatant could facilitate the role of NH₄⁺ as a monovalent cation, the replacement of the polyvalent cation in bound EPS, and even the extraction of EPS components from the surface of the sludge to form new SMP.     

Treatment of the refinery wastewater in a gas–liquid–solid three‐phase flow airlift loop bioreactor

Aerobic treatment of refinery wastewater was carried out in a 200 dm³ gas–liquid–solid three‐phase flow airlift loop bioreactor, in which a biological membrane replaced the activated sludge. The influences of temperature, pH, gas–liquid ratio and hydraulic residence time on the reductions in chemical oxygen demand (COD) and NH₄‐N were investigated and discussed. The optimum operation conditions were obtained as temperature of 25–35 °C, pH value of 7.0–8.0, gas–liquid ratio of 50 and hydraulic residence time of 4 h. The radial and axial positions had little influence on the local profiles of COD and NH₄‐N. Under the optimum operating conditions, the effluent COD and NH₄‐N were less than 100 mg dm^?3 and 15 mg dm^?3 respectively for more than 40 days, satisfying the national primary discharge standard of China (GB 8978‐1996). Copyright © 2005 Society of Chemical Industry     

Application of A/O‐MBR for treatment of digestate from anaerobic digestion of cow manure

BACKGROUND: Anaerobic digestion (AD) is widely used as an animal manure bioconversion technology. However, the effluent obtained from the digester during the wet‐AD process requires to be treated carefully before discharge if AD technology is to be developed as an effective and environmentally advantageous animal manure treatment. RESULTS: An anoxic/aerobic‐membrane bioreactor(A/O‐MBR) system has been developed for digestate treatment in an AD system treating cow manure. The performance of the A/O‐MBR system in terms of removal of nitrogen, COD and phosphorus were investigated. Results indicated that the average removal efficiencies of NH₄‐N⁺, COD and PO₄^3?‐P were 98.1%, 96.3% and 76.6%, respectively. The fouled membrane from the A/O‐MBR system was cleaned effectively using NaOH and a 30h soak time. CONCLUSION: This study suggests that it is technically feasible to use the A/O‐MBR for the treatment of digestate from a cow manure AD system, and can provide an environmentally acceptable way for the application of wet‐AD in animal manure treatment. Copyright © 2010 Society of Chemical Industry     

Biological Nutrient Removal Using a Novel Laboratory‐Scale Twin Fluidized‐Bed Bioreactor

The capability of biological nutrient removal from wastewater of a novel laboratory‐scale twin fluidized‐bed bioreactor (TFBBR) was studied. The work showed approximately 96 % organic matter, 84 % nitrogen, and 12 % phosphorus removal efficiencies in the first three phases of the study at influent synthetic municipal wastewater (SMW) flow rates of 150, 190, and 240 L/d, with corresponding organic loading rates of 1.3, 1.7, and 2.3 kg COD m^–3 d^–1 and nitrogen loading rates of 0.14, 0.18 and 0.25 kg N m^–3 d^–1. The TFBBR effluent was characterized by <1.0 mg NH₄‐N/L, <4.3 mg NO₃‐N/L, <6 mg TN/L, <6 mg SBOD/L, and 6–10 mg VSS/L. For the three phases, biomass yields of 0.06, 0.066, and 0.071 g VSS/g COD were observed, respectively, which was a significant further reduction in yield compared to the liquid‐solid circulating fluidized‐bed bioreactor technology developed and patented by this research group, of 0.12–0.16 g VSS/g COD. The very low yield was due to a longer solid retention time of 72–108 d.     

两种膜生物反应器工艺在养殖废水处理中的运行效果

采用动态膜生物反应器（dynamic membrane bioreactor,DMBR）和膜生物反应器（membrane bioreactor,MBR）两种处理工艺,研究在相同条件下对养殖废水的处理效果和运行条件。结果表明,不同溶解氧（dissolve oxygen,DO）条件下,DMBR和MBR对CODMn的去除率可达95%以上。DO为0～1 mg/L条件下,DMBR和MBR的总氮平均去除率分别达到71.4%、75.8%;在DO为2～3 mg/L条件下,DMBR和MBR的总氮平均去除率分别为46.3%、44.1%。DMBR和MBR两种工艺均能达到较好的污染物去除效果。MBR的过滤压差明显高于DMBR,低DO条件下（0～1 mg/L）的运行周期约为5天,DMBR采用重力流出水,运行周期约为10天,过滤压差最高时仅为3.97 kPa,在一定程度上克服MBR成本高、易污染等缺点。     

Effect of the sulfide concentration on zinc bio-precipitation in a single stage sulfidogenic bioreactor at pH 5.5

Dissolved zinc is present in natural waters and process streams generated by the mining and metallurgical industry. These streams usually have a low pH. By using sulfate reducing bacteria, sulfide can be produced that precipitates with zinc as zinc sulfide (sphalerite), which can be easily separated from the wastewater and even reused as zinc concentrate. In this study, a sulfate reducing gas-lift bioreactor was operated at pH 5.5 using hydrogen as electron donor for sulfate reduction. We demonstrate effective zinc removal (7.2 mmol L⁻¹ d⁻¹) with low zinc effluent concentrations (0.65–8.8 μM) in a system combining sulfide generation by sulfate reducing bacteria (7.2–10.6 mmol SO₄²⁻ L⁻¹ d⁻¹) at low pH (5.5) with the bio-precipitation of crystalline sphalerite. To investigate the effect of the sulfide excess on the settling properties of the sphalerite precipitates, the sulfide excess concentration was varied about two orders of magnitude (0.008–2.2 mM). The results show that crystalline sphalerite was formed in all cases, but larger particles with better settling properties were formed at lower sulfide concentrations.     

膜生物反应器工艺处理炼油废水中试研究

采用中空纤维膜生物反应器（MBR）工艺处理炼油废水,研究结果表明,MBR工艺可以有效的用于处理炼油废水,COD、氨氮和油去除率分别为92.9%、96.7%、84.7%,试验期间MBR出水COD平均为54.1mg/L,氨氮为1.85mg/L,油含量小于3.0mg/L。运行稳定后出水水质满足国家一级排放标准。     

Fenton试剂-MBR工艺处理环氧增塑剂化工废水的研究

针对含有H2O2的环氧增塑剂化工废水,采用Fenton-膜生物反应器（MBR）工艺进行处理。研究了不同的Fe2＋的投加量和反应时间对Fenton试剂处理废水的影响,讨论了不同水力停留时间（HRT）和进水COD浓度对MBR处理废水效率的影响。由结果可得,当Fenton试剂中Fe2＋投加量1.1 g/L、反应时间3 h、MBR的HRT 30 h和MLSS 7000～8000 mg/L时为最佳操作条件。处理出水CODCr为150～250 mg/L,总COD去除率为94%。     

Experimental study on application of the boundary layer theory for estimating steady aeration intensity of precoated dynamic membrane bioreactors

This paper introduced an approach that used precoated dynamic membrane (PDM) formed from powder activated carbon (PAC) on common terylene filter cloth instead of the conventional MF/UF membrane to build a membrane bioreactor (MBR) for wastewater treatment. The influence of aeration intensity for the PDM stability and the performance of the precoated dynamic membrane bioreactor (PDMBR) for treating municipal wastewater were investigated. The results of the rheological behavior of activated sludge in MBR showed that this liquor was approximated to Newtonian fluid while MLSS was less than 8100 mg/L. From the view of the mechanism of PDM formation process, when the thickness of laminar flow boundary layer was equal to that of PDM, PDMBR would run steadily, and this aeration intensity was defined as steady aeration intensity (172 L/h), which was estimated through using the boundary layer theory in the Newtonian hydrodynamics. In order to confirm the validity of theoretical calculation according to the flat membrane boundary layer theory, transmembrane pressure and treatment performance were observed when aeration intensity by gradual regulation began with oxygen supply aeration intensity (3–5 mg/L), increased up to theoretical calculation results, then till PDM detached. During PDMBR steadily running (31 days), effluent COD was less than 12.5 mg/L and its average removal efficiency was 97.5%, NH₄⁺–N was less than 5.3 mg/L and its average removal efficiency was 76.1%, while the transmembrane pressure just increased to 27 KPa. The results indicated that this operational mode could enhance the stability of PDMBR. During the late period, aeration intensity in practice in the range of 190–200 L/h was obtained. The experimental results concluded that application of the boundary layer theory in aeration intensity theoretical calculation was valid.     

Comparison of a sMBR and a CASP system for wastewater reclamation and re-use

The performance of a submerged membrane bioreactor (sMBR) for municipal wastewater reclamation and re-use was compared with that of a current classic activated sludge process (CASP). The average chemical oxygen demand (COD) of CASP effluent was 75 mg/l, while the average COD of sMBR filtrate was 15 mg/l. In general, COD removal was above 98%. However, the best results were obtained at a sludge rentention time (SRT) of 50 days. The total phosphorus (TP) content of the filtrate decreased to a level <1 mg/l under aerobic conditions in which aeration occurred continuously. It was shown that the filtrate TP and orthoposphate (Orto-P) concentrations increased dramatically during the periods of intermittent aeration because phosphorus is released under anoxic conditions. In the CASP effluent, the average TP and Orto-P were 7.9 mg/l and 7.1 mg/l, respectively. The filtrate was free of suspended solids (SS) and total coliform bacteria. The effluent SS in the CASP was 40 mg/l. The turbidity removal in the sMBR reached almost 99%, i.e. generally less than 1 NTU, while the average turbidity of the CASP effluent was almost 15 NTU. The removal of ammonium nitrogen (NH₄⁺-N) in the sMBR was almost 99.8%. In addition, the nitrate concentration in the filtrate decreased to 2.4 mg/l under both aerobic & anoxic conditions. It was shown that both nitrification and denitrification could be successfully reduced through intermittent aeration. Average total Kjeldehl nitrogen (TKN) and NH₄⁺-N in the CASP effluent were 30.2 mg/l and 20 mg/l, respectively, i.e. the nitrification efficiency was 42.9%, and the denitrification value was not available. When these results are compared with those in the CASP, it indicated that the sMBR could be successfully used for reclamation and re-use of municipal wastewater.     

Continuous operation of membrane bioreactor treating toluene vapors by Burkholderia vietnamiensis G4

A laboratory-scale biofilm membrane bioreactor inoculated with Burkholderia vietnamiensis G4 was examined to treat toluene vapors in a waste gas stream. The gas feed side and nutrient solution were separated by a composite membrane consisting of a porous polyacrylonitrile (PAN) support layer coated with a very thin (0.3 μm) dense polydimethylsiloxane (PDMS) top layer. After inoculation, a biofilm developed on the dense layer. The biofilm membrane bioreactor was operated continuously at different residence times (28–2 s) and loading rates (1.2–26.7 kg m⁻³ d⁻¹), with inlet toluene concentrations ranging from 0.21 to 4.1 g m⁻³. The overall performance of the membrane bioreactor was evaluated over a period of 165 days. Removal efficiencies ranging from 78% to 99% and elimination capacities from 4.2 to 14.4 kg m⁻³ d⁻¹ were observed after start-up period depending on the mode of operation. A maximum elimination capacity of 14.4 kg m⁻³ d⁻¹ was observed at a loading rate of 17.4 kg m⁻³ d⁻¹. Overall, the results illustrate that biofilm membrane reactors can potentially be more effective than conventional biofilters and biotrickling filters for the treatment of air pollutants such as toluene.     

Phenolic wastewater treatment in a three‐phase fluidised bed bioreactor containing low density particles

The treatment of phenolic wastewater was investigated in a gas–liquid–solid fluidised bed bioreactor containing polypropylene particles of density 910 kg m^?3. Measurements of chemical oxygen demand (COD) versus residence time (t) were performed for various ratios of settled bed volume to bioreactor volume (V_b/V_R) and air velocities (u) to determine the values of (V_b/V_R) and u for which the largest reduction in COD occurred. Optimal operation, corresponding to the largest COD removal, was attained when the bioreactor was controlled at the ratio (V_b/V_R) = 0.55 and an air velocity u = 0.036 m s^?1. Under these conditions, the value of COD was practically at steady state for times greater than 50 h. At this steady state, only about 50% COD removal was achieved in the treatment of a ‘raw’ wastewater (no mineral salts added), whereas in the operation with wastewater enriched in nutrient salts approximately 90% COD removal was attained. The following amount of mineral salts (mg dm^?3): (NH₄)₂SO₄—500; KH₂PO₄—200; MgCl₂—30; NaCl—30; CaCl₂—20; and FeCl₃—7, when added to wastewater before treatment, was sufficient for biomass growth. The application of low density particles (used as biomass support) in a bioreactor allowed the control of biomass loading in the apparatus. In the cultures conducted after change in (V_b/V_R) at a set u, the steady state mass of cells grown on the particles was achieved after approximately 6 days of operation. With change in u at a set (V_b/V_R), the new steady state biomass loading occurred after culturing for about 2 days. Phenolic wastewater was successfully treated in a bioreactor. In the operation conducted in a bioreactor optimally controlled at (V_b/V_R) = 0.55, u = 0.036 m s^?1 and t = 50 h, conversions greater than 99% were achieved for all phenolic constituents of the wastewater. Conversions of about 90% were attained for other hydrocarbons. Copyright © 2005 Society of Chemical Industry     

Degradation of dye wastewater in a thin-film photoelectrocatalytic (PEC) reactor with slant-placed TiO2/Ti anode

A thin-film photoelectrocatalytic (PEC) reactor with slant-placed TiO₂/Ti anode was developed and successfully applied to degrade Rhodamine B (RhB) and textile effluent. Using a 5–150 mg L⁻¹ RhB solution as the model system, thin-film PEC removed total color and TOC by 99–28% and 78–15%, respectively, in 1 h, which is much higher than 82–7% and 60% to zero by conventional PEC. The enhanced treatment efficiency achieved by thin-film PEC process was attributed to the significantly reduced path length of irradiation light source. The wastewater was kept circulating during the experiments to timely refresh the aqueous film on the TiO₂/Ti anode and promote the mass transfer of the target pollutants and the degradation products in the bulk solution. The thin-film PEC reactor can degrade both simulated and real dye wastewater efficiently under UV light irradiation. Results suggested that thin-film PEC was particularly superior for treating a high concentration solution. The thin-film PEC reactor was also applied to treat RhB solution efficiently under solar light irradiation. The recycle experiments demonstrated excellent stability and reliability of the slant-placed TiO₂/Ti anode. This study proposed a simple and effective method to design PEC reactor applicable for industrial dye wastewater treatment.     

Effect of COD/NO3-N ratio on the performance of a hybrid UASB reactor treating phenolic wastewater

The effect of COD/O₃⁻-N ratio on the biodegradation of complex phenolic mixture was studied in bench scale hybrid upflow anaerobic sludge blanket (HUASB) reactors. HUASB reactor is a combination of a UASB unit at the lower part and an anaerobic fixed film at the upper end. The aim of this study was to evaluate the biodegradability of phenolic mixture (from synthetic coal wastewater) as the only carbon and energy source in continuous experiments using nitrate as the final electron acceptor. Synthetic coal wastewater contained phenol (490 mg/L); m-,o-,p-cresols (123.0 mg/L, 58.6 mg/L, 42 mg/L); 2,4-, 2,5-, 3,4- and 3,5 dimethyl phenols (6.3 mg/L, 6.3 mg/L, 4.4 mg/L and 21.3 mg/L) as major phenolic compounds representing the complex phenolic mixture. Nitrate nitrogen loading was increased from 0.11 g/m³/d to 0.5 g/m³/d in order to keep COD/NO₃⁻-N ratio as 20.1, 14.85, 9.9, 6.36 and 4.45. An input phenolics concentration of 752 mg/L and hydraulic retention time (HRT) of 24 h was maintained through out the study. Removal of phenolic mixture was found to increase with the lowering of COD/NO₃⁻-N ratio. Maximum phenolics removal of 98% was achieved at a COD/NO₃⁻-N ratio of 6.36. However, phenolics removal got adversely affected when COD/NO₃⁻-N ratio was reduced below 6.36. A nitrogen production efficiency of 78% was obtained according to nitrate consumption. Simultaneous denitrification and methanogenesis was observed in all the reactors throughout the study, demonstrating that denitrification is a feasible alternative for the treatment of coal wastewater. Granules degrading complex phenolic mixture were of diameter 1.6–2.25 mm.     

Pilot‐scale anaerobic/anoxic/oxic/oxic biofilm process treating coking wastewater

BACKGROUND: Biological treatment efficiency of coking wastewater is rather poor, especially for chemical oxygen demand (COD) and ammonia‐nitrogen (NH$_{4}^{+}$ ‐N) removal due to its complex composition and high toxicity. RESULTS: A pilot‐scale anaerobic/anoxic/oxic/oxic (A²/O²) biofilm system has been developed to treat coking wastewater, focusing attention on the COD and NH$_{4}^{+}$ ‐N removal efficiencies. Operational results over 239 days showed that hydraulic retention time (HRT) of the system had a great impact on simultaneous removals of COD and NH$_{4}^{+}$ ‐N. At HRT of 116 h, total removal efficiencies of COD and NH$_{4}^{+}$ ‐N were 92.3% and 97.8%, respectively, reaching the First Grade discharge standard for coking wastewater in China. Adequate HRT, anoxic removal of refractory organics and two‐step aerobic bioreactors were considered to be effective measures to obtain satisfactory coking effluent quality using the A²/O² biofilm system. The correlation between removal characteristics of pollutants and spatial distributions of biomass along the height of upflow bioreactors was also revealed. CONCLUSION: The study suggests that it is feasible to apply the A²/O² biofilm process for coking wastewater treatment, achieving desirable effluent quality and steady process performance. © 2012 Society of Chemical Industry     

A/O膜生物反应器生活污水回用处理中试研究

采用中试规模的缺氧-好氧一体式膜生物反应器(A/O MBR)对生活污水处理回用进行了试验研究。试验结果表明,该工艺处理效果优良,系统对COD、氨氮的平均去除率分别为94.7%和99.08%,膜分离截留对COD的去除起到了决定性作用,生物对NH4 -N的去除占主要作用,膜本身对NH4 -N的直接去除作用不大。出水COD、氨氮的浓度分别为16.02 mg/L和0.35 mg/L,出水水质优于城市杂用水水质标准(GB/T l8920-2002)和河道景观环境用水水质标准(GB/T l8921-2002)。该系统运行稳定,具有较强的抗冲击负荷能力,工艺基本无污泥排放。     

MBR-光催化氧化处理印染废水的试验研究

利用MBR-光催化氧化的组合工艺处理某纺织园区综合废水,对反应装置进行了连续运行效果的考察.结果表明,MBR对废水COD、浊度,色度降解率分别达到93.5%、99.9%和98.9%;MBR中污泥沉降性能明显优于SBR,能有效控制污泥膨胀现象;出水的透光性大大提高,经光催化氧化后COD、BOD、浊度、色度分别稳定在35.0mg·L~(-1)、2.7 mg·L~(-1),2.3NTU、3倍,水质达到GB 18918-2002的一级A排放标准和CJ/T48-1999的生活杂用水要求.     

Diplatinum(III) [Cl2(μ2-amidinate)4] compound derived from air oxidation of mononuclear cis-[Pt(NH3)2(amidine-κ)2] complex

The dinuclear platinum(III) complex [Pt₂Cl₂{μ₂-N(H)C(Et)N(H)}₄] (2) has been prepared by heating cis-[Pt(NH₃)₂{NHC(NH₂)Et}₂](Cl)₂ (cis-1) under aeration conditions in an EtOH/H₂O mixture at 70 °C for 2 d and it was characterized by elemental analyses (C, H, N), ESI⁺-MS, IR, ¹H and ¹³C NMR spectroscopies and also by X-ray diffraction. Complex 2 represents the second Pt^III dimer stabilized by the amidinate ligand ever known and it has a lantern-type structure with four amidinate ligands bridging two Pt^III centers with Pt–Pt distance of 2.4809(2) Å.     

一体式膜生物反应器作为反渗透预处理技术的试验研究

为给某企业的反渗透系统提供稳定的优质进水,采用一体式膜生物反应器对某城市污水处理厂二级出水进行了深度处理中试试验。研究结果表明:在进水COD的质量浓度为7～15 mg/L时,色度为20～50度,浊度为0.70～3.57 NTU,膜通量10.0～13.75 L/(m2.h)、跨膜压差0.019～0.038 MPa、曝气量20 m3/h、制水时间40min、停机时间3 min、HRT 3.6～5.0 h条件下,MBR系统出水COD质量浓度小于10 mg/L,色度小于30度,浊度小于1 NTU,SDI15小于3,满足反渗透系统进水水质要求;MBR系统出水水质稳定,具有较强的耐冲击负荷能力。另外,探讨了MBR系统的跨膜压差与膜通量之间的关系。