Effect of sludge age on performance of an activated sludge unit treating 2,4 dichlorophenol-containing synthetic wastewater

Wastewaters containing chlorophenol compounds are difficult to treat by biological means because of toxic effects of chlorophenols on microorganisms. Synthetic wastewater containing 2,4 dichlorophenol (DCP) was biologically treated in an activated sludge unit at different sludge ages varying between 5 and 30 days while the feed COD, DCP contents and hydraulic residence time (HRT) were constant. Effects of sludge age on COD, DCP and toxicity removals were investigated. Increases in sludge age caused significant increases in biomass concentration in the aeration tank, which resulted in increases in percent COD, DCP and toxicity removals. COD removal increased from 58 to 90%, while DCP and toxicity removals increased from 15 to 100% and from 38 to 100%, respectively, when the sludge age was raised from 5 to 30 days. Resazurin method based on dehydrogenase activity was used for assessment of the feed and effluent wastewater toxicity. Sludge volume index (SVI) decreased with increasing sludge age indicating improved settling characteristics of the sludge at high sludge ages. Operation at a sludge age of 25 days resulted in more than 90% COD and nearly 100% DCP and toxicity removal with an SVI value of 108 ml g⁻¹ under the experimental conditions tested.     

Anaerobic biodegradation of a petrochemical waste-water using biomass support particles

During the anaerobic biodegradation of effluent from a dimethyl terephthalate (DMT) manufacturing plant, reduction in chemical oxygen demand (COD) degradation and biogas formation was observed after the waste-water concentration exceeded 25% of added feed COD. This condition reverted back to normal after 25–30 days when the DMT waste-water concentration in the feed was brought down to a non-toxic level. However, the above effects were observed only after the concentration of DMT waste-water reached more than 75% of added feed COD when biomass support particles (BSP) were augmented to the system. In the BSP system, a biomass concentration of up to 7000 mg/l was retained and the sludge retention time increased to > 200 days compared to 2200 mg/l and 8–10 days, respectively, in the system without BSP (control). Formaldehyde in the waste-water was found to be responsible for the observed toxicity. The BSP system was found to resist formaldehyde toxicity of up to 375 mg/l as against 125 mg/l in the control system. Moreover, the BSP system recovered from the toxicity much faster (15 days) than the control (25–30 days). The advantages of the BSP system in anaerobic treatment of DMT waste-water are discussed. Correspondence to: C. Ramakrishna     

Characterization and biological treatment of ceramic industry wastewater

Ceramic industry wastewaters not only contain high suspended and total solids but also significant amounts of dissolved organics resulting in high BOD or COD loads. Suspended solids can be removed from the wastewater by chemical precipitation. However, dissolved BOD/COD compounds can only be removed by biological or chemical oxidation. Effluent wastewater from chemical sedimentation stage of EGE CERAMIC industry was characterized and subjected to biological treatment in a laboratory scale activated sludge unit. Experiments were conducted at different hydraulic and solids retention times. The best results were obtained with Š_c=20 h of hydraulic and Š_c=20 days of solids retention times (sludge age) resulting in effluent COD concentration of 40 mg/l from a feed wastewater of 720 mg/l COD content. The suspended solids content of the activated sludge effluent was approximately 52 mg/l.     

UASB-化学混凝技术处理草浆造纸废水的研究

采用UASB-化学混凝技术组合对草浆造纸废水进行处理。结果表明,接种颗粒污泥的二级启动,大大缩短了反应器的启动时间。在水力停留时间(HRT)6 h,进水COD逐渐提高的情况下对颗粒污泥进行驯化,20 d后pH、COD去除率趋于稳定。另外,通过L9(34)正交试验,研究了混凝中4因子影响大小的排序,并在最优条件下对UASB反应器出水进行混凝处理。组合技术处理的出水水质指标符合国家造纸工业污水排放标准。     

Biological cyanide degradation in aerobic fluidized bed reactors: treatment of almond seed wastewater

The continuous aerobic transformation of synthetic cyanide waste-water, amygdalin solutions and almond seed extract containing cyanide was investigated in several fluidized bed reactors. Various inocula consisting of activated sludge or soil slurry were used. Successful inoculation was achieved with simple soil slurry. No significant influence was found between the performance of the systems inoculated with a cyanide contaminated soil and a garden soil. The performance and stability of the reactors with respect to degradation rate were tested for a range of cyanide loading conditions, with feed containing only cyanide, and with different additional carbon sources, as well as various CN ratios at a hydraulic retention time of 24 h. No growth with cyanide as the sole source of carbon and nitrogen was observed. The system with lactate as the organic C-source was capable of operating at cyanide concentrations of 160 ppm cyanide with a conversion rate of 0.125 kg cyanide/m³ d. Ammonia was the end product and the effluent concentration was 0.5 ppm CN^–. The systems with ethanol as the organic C-source could degrade only 0.05 kg cyanide/m³ d, whose feed concentration was 60 ppm cyanide. Amygdalin, an organic cyanide-containing compound present in stone fruit seeds, was fed as a model substrate. Degradation rates up to 1.2 kg COD/m³ d could be measured with no free or organically bound cyanide in the effluent. These rates were limited by oxygen transfer, owing to the large amount of degradable COD. The further investigations with almond seed extracts, confirmed the applicability of the aerobic process to treat food-processing waste streams having low concentrations of cyanide with high COD content.The authors with to thank Dr. Ö.M. Kurt for useful discussions.     

Anaerobic treatment of pre-hydrolysate liquor (PHL) from a rayon grade pulp mill: pilot and full-scale experience with UASB reactors

Pilot studies were carried out for the treatment of pre-hydrolysate liquor (PHL), a high strength effluent (COD: 70,000-80,000 mg/l) emanating from a rayon grade pulp mill using up-flow anaerobic sludge blanket reactor (UASB). Substrate inhibition was avoided with optimum COD feed of around 25,000 mg/l. This was achieved by diluting the PHL with a low strength effluent stream known as alkali back wash (ABW) available in the plant and also by partially recycling the reactor liquid outlet. An optimum organic loading rate (OLR) of 10 could be achieved with a COD reduction of 70-75%, a BOD reduction of 85-90% and a methane yield of 0.31-0.33 m3/kg of COD reduced. The pilot scale studies also revealed that addition of milk of lime (MOL) was essential for neutralization and buffering and DAP and urea to supplement the nutrients in the PHL. Based on the pilot studies, a full-scale high rate biomethanation plant was designed and erected for treating the PHL, which after some modification showed similar performance for COD, BOD reduction and methane yield.     

Thermophilic treatment of bulk drug pharmaceutical industrial wastewaters by using hybrid up flow anaerobic sludge blanket reactor

The hybrid up flow anaerobic sludge blanket reactor was evaluated for efficacy in reduction of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of bulk drug pharmaceutical wastewater under different operational conditions. The start-up of the reactor feed came entirely with glucose, applied at an organic loading rate (OLR) 1 kg COD/m³ d. Then the reactor was studied at different OLRs ranging from 2 to 11 kg COD/m³ d with pharmaceutical wastewater. The optimum OLR was found to be 9 kg COD/m³ d, where we found 65–75% COD and 80–94% of BOD reduction with biogas production containing 60–70% of methane and specific methanogenic activity was 320 ml CH₄/g-VSS d. By the characterization studies of effluent using GC–MS, the hazardous compounds like phenol, l,2-methoxy phenol, 2,4,6-trichloro phenol, dibutyl phthalate, 1-bromo naphthalene, carbamazepine and antipyrine were present. After the treatment, these compounds degraded almost completely except carbamazepine. Thermophilic methanothrix and methanosaetae like bacteria are present in the granular sludge.     

Effect of effluent recycling and shock loading on the biodegradation of complex phenolic mixture in hybrid UASB reactors

This study describes the feasibility of anaerobic treatment of synthetic coal wastewater using four identical 13.5L (effective volume) bench scale hybrid up flow anaerobic sludge blanket (HUASB) reactors (R1, R2, R3 and R4) under mesophilic (27+/-5 degrees C) conditions. Synthetic coal wastewater with an average chemical oxygen demand (COD) of 2240 mg/L and phenolics concentration of 752 mg/L was used as substrate. Effluent recirculation was employed at four different effluent to feed recirculation ratios (R/F) of 0.5, 1.0, 1.5 and 2.0 for 100 days to study the effect of recirculation on the performance of the reactors. Phenolics and COD removal was found to improve with increase in effluent recirculation. An effluent to feed recycle ratio of 1.0 resulted in maximum removal of phenolics and COD. Phenolics and COD removal improved from 88% and 92% to 95% each, respectively. The concentration of volatile fatty acids in the effluent was lower than the influent when effluent to feed recirculation was employed. Effect of shock loading on the reactors revealed that phenolics shock load up to 2.5 times increase in the normal input phenolics concentration in the form of continuous shock load for 4days did not affect the reactors performance irreversibly.     

Aerobic granular sludge formation for high strength agro-based wastewater treatment

The present study investigates the formation of aerobic granular sludge in sequencing batch reactor (SBR) fed with palm oil mill effluent (POME). Stable granules were observed in the reactor with diameters between 2.0 and 4.0 mm at a chemical oxygen demand (COD) loading rate of 2.5 kg COD m⁻³ d⁻¹. The biomass concentration was 7600 mg L⁻¹ while the sludge volume index (SVI) was 31.3 mL g SS⁻¹ indicating good biomass accumulation in the reactor and good settling properties of granular sludge, respectively. COD and ammonia removals were achieved at a maximum of 91.1% and 97.6%, respectively while color removal averaged at only 38%. This study provides insights on the development and the capabilities of aerobic granular sludge in POME treatment.     

Effects of media composition on substrate removal by pure and mixed bacterial cultures

Continuous culture experiments with identical experimental designs were run with a mixed microbial community of activated sludge origin and an axenic bacterial culture derived from it. Each culture received 2-chlorophenol (2-CP) at a concentration of 160 mg/L as COD and L-lysine at a concentration of 65 mg/L as COD. A factorial experimental design was employed with dilution rate and media composition as the two controlled variables. Three dilution rates were studied: 0.015, 0.0325, and 0.05 h^–1. Media composition was changed by adding four biogenic compounds (butyric acid, thymine, glutamic acid and lactose) in equal COD proportions at total concentrations of 0, 34, 225, and 1462 mg/L as COD. The measured variables were the effluent concentrations of 2-CP as measured by the 4-aminoantipyrene test and lysine as measured by the o-diacetylbenzene procedure. The results suggest that community structure and substrate composition play important roles in the response of a microbial community to mixed substrates. The addition of more biogenic substrates to the axenic culture had a deleterious effect on the removal of both lysine and 2-CP, although the effect was much larger on lysine removal. In contrast, additional substrates had a positive effect on the removal of 2-CP by the mixed community and much less of a negative effect on the removal of lysine. The dilution rate at which the cultures were growing had relatively little impact on the responses to the additional substrates.Abbreviations COD chemical oxygen demand - 2-CP 2-chlorophenol - DOC dissolved organic carbon - MDL method detection limit - SS suspended solids     

Kinetic studies of constitutive human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression in continuous culture of <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Extracellular human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression was studied under the control of the GAP promoter in recombinant Pichia pastoris in a series of continuous culture runs (dilution rates from 0.025 to 0.2 h⁻¹). The inlet feed concentration was also varied and the steady state biomass concentration increased proportionally demonstrating efficient substrate utilization and constancy of the biomass yield coefficient (Y_x/s) for a given dilution rate. The specific product formation rate (q_P) showed a strong correlation with dilution rates demonstrating growth associated product formation of hGM-CSF. The volumetric product concentration achieved at the highest feed concentration (4×) and a dilution rate of 0.2 h⁻¹ was 82 mg l⁻¹ which was 5-fold higher compared to the continuous culture run with 1× feed concentration at the lowest dilution rate thus translating to a 40 fold increase in the volumetric productivity. The specific product yield (Y_P/X) increased slightly from 2 to 2.5 mg g⁻¹, with increasing dilution rates, while it remained fairly invariant, for all feed concentrations demonstrating negligible product degradation or feed back inhibition. The robust nature of this expression system would make it easily amenable to scale up for industrial production.     

Removal of Cu(II) ions by biosorption onto powdered waste sludge (PWS) prior to biological treatment in an activated sludge unit: A statistical design approach

Biological treatment of synthetic wastewater containing Cu(II) ions was realized in an activated sludge unit with pre-adsorption of Cu(II) onto powdered waste sludge (PWS). Box-Behnken experimental design method was used to investigate Cu(II), chemical oxygen demand (COD) and toxicity removal performance of the activated sludge unit under different operating conditions. The independent variables were the solids retention time (SRT, 5–30 d), hydraulic residence time (HRT, 5–25 h), feed Cu(II) concentration (0–50 mg L^?1) and PWS loading rate (0–4 g h^?1) while percent Cu(II), COD, toxicity (TOX) removals and the sludge volume index (SVI) were the objective functions. The data were correlated with a quadratic response function (R² = 0.99). Cu(II), COD and toxicity removals increased with increasing PWS loading rate and SRT while decreasing with the increasing feed Cu(II) concentration and HRT. Optimum conditions resulting in maximum Cu(II), COD, toxicity removals and SVI values were found to be SRT of 30 d, HRT 15 h, PWS loading rate 3 g h^?1 and feed Cu(II) concentration of less than 30 mg L^?1.     

Sequencing Batch Reactor Biodegradation of Hydrolyzed Sarin as Sole Carbon Source

The chemical nerve agent sarin (o-isopropyl methylphosphonofluoridate) was hydrolyzed at 7.18 weight percent in aqueous sodium hydroxide yielding primarily o-isopropyl methylphosphonic acid (IMPA). This hydrolysate was diluted and fed as sole carbon source to activated sludge in an aerobic sequencing batch reactor. Feed chemical oxygen demand (COD) concentrations ranged from approximately 2500 mg/L (initial) to 5000 mg/L (final). The reactor was operated essentially on a 15-day hydraulic residence time. Overall COD removal efficiency was 86.2% and the IMPA in the feed was converted to methylphosphonic acid. MICROTOX® and Daphnia magna aquatic toxicity testing showed the effluent to be of very low toxicity to aquatic test organisms. The final MPA product was effectively absorbed by Phoslock?, which is a lanthanide modified clay.     

Integrated biological process for olive mill wastewater treatment

The biological process for OMW treatment is based on an aerobic detoxification step followed by methanization step and aerobic post-treatment.The first aerobic detoxification step of OMW supplemented with sulfate and ammonium was carried out by the growth of Aspergillus niger in a bubble column. This step decreased OMW toxicity and increased its biodegradability because of phenolic compounds degradation. Growth of A. niger resulted in 58% COD removal, with production of biomass containing 30% proteins (w/w). Filtration of OMW was enhanced by this fermentation because the suspended solids were trapped in the mycelium. The filtrate liquid was then methanized using an anaerobic filter packed with flocoor. This reactor showed a short start up and a good stability. COD removal was around 60% and the methane yield (1 CH₄/g COD removed) was close to the theoretical yield.The anaerobic filter effluent was treated in an activated sludge fluidized reactor containing olive husk as a packing material. Husks were maintained in fluidization state by the aeration. This step induces COD removal at 45% and sludge (up to 2 g/dm³).The entire process allowed a global COD reduction up to 90%; however, the black colour due to polyphenolic compounds with high molecular weight persisted.     

Effect of organic loading rate on the performance of an up-flow anaerobic sludge blanket reactor treating olive mill effluent

The primary objective of this study was to evaluate the effects of the organic loading rate on the performance of an up-flow anaerobic sludge blanket (UASB) reactor treating olive mill effluent (OME), based on the following indicators: (i) chemical oxygen demand (COD) removal efficiency; and (ii) effluent variability (phenol, suspended solids, volatile fatty acids, and pH stability). The UASB reactor was operated under different operational conditions (OLRs between 0.45 and 32 kg COD/m³·day) for 477 days. The results demonstrated that the UASB reactor could tolerate high influent COD concentrations. Removal efficiencies for the studied pollution parameters were found to be as follows: COD, 47∼92%; total phenol, 34∼75%; color, 6∼46%; suspended solids, 34∼76%. The levels of VFAs in the influent varied between 310 and 1,750 mg/L. Our measurements of the VFA levels indicated that some of the effluent COD could be attributed to VFAs (principally acetate, butyrate, iso-butyrate, and propionate) in the effluent, which occurred at levels between 345 and 2,420 mg/L. As the OLRs were increased, more VFAs were measured in the effluent. A COD removal efficiency of 90% could be achieved as long as OLR was kept at a level of less than 10 kg COD/m³·day. However, a secondary treatment unit for polishing purposes is necessary to comply with discharge standards.     

Sequencing Batch Reactor Biodegradation of Hydrolyzed Sarin as Sole Carbon Source

The chemical nerve agent sarin (o-isopropyl methylphosphonofluoridate) was hydrolyzed at 7.18 weight percent in aqueous sodium hydroxide yielding primarily o-isopropyl methylphosphonic acid (IMPA). This hydrolysate was diluted and fed as sole carbon source to activated sludge in an aerobic sequencing batch reactor. Feed chemical oxygen demand (COD) concentrations ranged from approximately 2500 mg/L (initial) to 5000 mg/L (final). The reactor was operated essentially on a 15-day hydraulic residence time. Overall COD removal efficiency was 86.2% and the IMPA in the feed was converted to methylphosphonic acid. MICROTOX® and Daphnia magna aquatic toxicity testing showed the effluent to be of very low toxicity to aquatic test organisms. The final MPA product was effectively absorbed by Phoslock™, which is a lanthanide modified clay.     

Effect of pH on phase separated anaerobic digestion

A pilot scale experiment was performed for a year to develop a two-phase anaerobic process for piggery wastewater treatment (COD: 6,000 mg/L, BOD: 4,000 mg/L, SS: 500 gm/L, pH 8.4, alkalinity 6,000 mg/L). The acidogenic reactor had a total volume of 3 m³, and the methanogenic reactor, an, anaerobic up-flow sludge filter, combining a filter and a sludge bed, was also of total volume 3 m³ (1.5 m³ of upper packing material). Temperatures of the acidogenic and methanogenic reactors kept at 20°C and 35°C., respectively. When the pH of the acidogenic reactor was controlled at 6.0–7.0 with HCl, the COD removal efficiency increased from 50 to 80% over a period of six months, and as a result, the COD of the final effluent fell in the range of 1,000–1,500 mg/L. BOD removal efficiency over the same period was above 90%, and 300 to 400 mg/L was maintained in the final effluent. The average SS in the final effluent was 270 mg/L. The methane production was 0.32 m³ CH₄/kg COD_removed and methane content of the methanogenic reactor was high value at 80–90%., When the pH of the acidogenic reactor was not controlled over the final two months, the pH reached 8.2 and acid conversion decreased compared with that of pH controlled, while COD removal was similar to the pH controlled operation. Without pH control, the methane content in the gas from methanogenic reactor improved to 90%, compared to 80% with pH control.     

Biological treatment of high strength wastewater by fed-batch operation

Biological treatment systems for high strength wastewaters are usually operated in continuous mode such as activated sludge systems. When operated at steady-state, continuous systems result in constant effluent standards. However, in the presence of shock loadings and/or toxic compounds in feed wastewater, system performance drops quite significantly as a result of partial loss of microbial activity. In fed-batch operation, wastewater is fed to the aeration tank with a flow rate determined by effluent standards. In this type of operation, wastewater can be fed to biological oxidation unit intermittently or continuously with a low flow rate without any effluent removal. Feed flow rate is adjusted by measuring COD concentration in the effluent. As a result of intermittent addition of wastewater high COD concentrations and toxic compounds are diluted in large volume of aeration tank and inhibition effects of those compounds are reduced. As a result, biological oxidation of these compounds take place at a much higher rate. In order to show the aforementioned advantage of fed-batch operation, a high strength synthetic wastewater consisting of diluted molasses, urea, KH₂PO₄ and MgSO₄ was treated in an biological aeration tank by fed-batch operation. Organisms used were an active and dominant culture of Zooglea ramigera commonly encountered in activated sludge operations. COD removal kinetics was found to be first order and the rate constant was determined.     

菌藻共生系统对序批式反应器处理养猪废水脱氮除磷效果及微生物群落结构的影响

【背景】养猪废水作为高浓度有机废水,是导致我国农业面源污染的主要因素之一。目前采用菌藻共生系统处理养猪废水越来越受到关注,与传统序批式反应器(Sequencing Batch Reactor,SBR)相比,藻辅助SBR具有提高脱氮除磷效果、增加污泥活性和降低能源消耗的特点。【目的】针对SBR中菌藻共生系统对养猪废水脱氮除磷效能的影响,比较分析菌藻共生系统与常规SBR系统中污泥特性及微生物群落结构特征差异。【方法】在室温条件下分别平行运行SBR+微藻(R1)和作为对照系统不添加微藻的SBR(R2)。监测R1和R2系统废水处理效果,污泥的粒径、沉降性和代谢产物等污泥特性。利用变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis,DGGE)技术分析R1和R2系统中的微生物种类和分布。【结果】与对照R2反应器相比,R1的化学需氧量(Chemical Oxygen Demand,COD)去除率提高了5.1%,NH4+-N提高了20.3%,总氮(Total Nitrogen,TN)提高了19.4%,总磷(Total Phosphorus,TP)提高了23.9%。进一步对反应器中的污泥特性进行分析发现,与R2相比,R1的胞外聚合物(ExtracellularPolymericSubstances,EPS)平均含量提高3.7%,可溶性微生物产物(Soluble MicrobialProduct,SMP)平均增加了38.5%。同时R1的污泥粒径较R2提高了14.8%,污泥体积指数(Sludge Volume Index,SVI)值较R2降低了11.7%,污泥的好氧呼吸速率(Specific Oxygen Uptake Rate,SOUR)较R2提高了64.8%,而且稳定的菌藻共生系统的形成进一步减少反应器出水中的悬浮固体浓度,表明藻类的添加对R1污泥特性具有改良作用【结论】R1反应器形成的菌藻共生体系可进一步优化微生物群落结构,其中放线菌纲(Actinobacteria)、α-变形菌纲(Alphaproteobacteria)和γ-变形菌纲(Gammaproteobacteria)为R1反应器的主要菌群,对养猪废水的处理起到重要作用。R1反应器中的藻类主要为链带藻属(Desmodesmus)和尖带藻属(Acutodesmus),对养猪废水的脱氮除磷起到重要作用。     

Kinetic Modelling and Characterization of Microbial Community Present in a Full-Scale UASB Reactor Treating Brewery Effluent

The performance of a full-scale upflow anaerobic sludge blanket (UASB) reactor treating brewery wastewater was investigated by microbial analysis and kinetic modelling. The microbial community present in the granular sludge was detected using fluorescent in situ hybridization (FISH) and further confirmed using polymerase chain reaction. A group of 16S rRNA based fluorescent probes and primers targeting Archaea and Eubacteria were selected for microbial analysis. FISH results indicated the presence and dominance of a significant amount of Eubacteria and diverse group of methanogenic Archaea belonging to the order Methanococcales, Methanobacteriales, and Methanomicrobiales within in the UASB reactor. The influent brewery wastewater had a relatively high amount of volatile fatty acids chemical oxygen demand (COD), 2005 mg/l and the final COD concentration of the reactor was 457 mg/l. The biogas analysis showed 60–69 % of methane, confirming the presence and activities of methanogens within the reactor. Biokinetics of the degradable organic substrate present in the brewery wastewater was further explored using Stover and Kincannon kinetic model, with the aim of predicting the final effluent quality. The maximum utilization rate constant U _max and the saturation constant (K _B) in the model were estimated as 18.51 and 13.64 g/l/day, respectively. The model showed an excellent fit between the predicted and the observed effluent COD concentrations. Applicability of this model to predict the effluent quality of the UASB reactor treating brewery wastewater was evident from the regression analysis (R ²?=?0.957) which could be used for optimizing the reactor performance.