Anaerobic treatment of wastewater from a food-manufacturing plant with a low concentration of organic matter and regeneration of usable pure water

Wastewater from a food-manufacturing plant with a low concentration of organic matter below 100 mg/l TOC was first treated at 37°C in an anaerobic fluidized-bed reactor (AFBR) or in an upflow anaerobic sludge blanket (UASB). The TOC removal efficiency in both reactors decreased from 85% to 65% as the influent TOC concentration decreased from 100 to 35 mg/l at a hydraulic retention time (HRT) of 6 h. Treatment at an HRT of 4 h resulted in an effluent TOC concentration of 11 to 15 mg/l. The concentration of suspended solids in the effluent could be reduced to 20 mg/l, which corresponded to 7% of that of the influent. The effluent from both reactors was then treated anaerobically in a fixed-bed reactor system. The TOC concentration and optical density (OD) of the effluent from the aerobic treatment were reduced to 5 mg/l and 0.005, respectively, at an HRT of 2 h. When anaerobically or aerobically treated effluent was passed over an activated carbon column, the effluent TOC concentration was reduced to 2 to 3 mg/l. The conductivity of 1.3 mS/cm in raw wastewater, which was not removed through the above treatments, was reduced to 0.001 mS/cm on an ion-exchange resin column. An effluent quality corresponding to that of ultra-pure water for industrial use was finally attained by the treatment in this multi-step system.     

The effect of pretreatment on anaerobic activity of olive mill wastewater using batch and continuous systems

This study was focused on several physico-chemical and biological treatment methods that may affect the reduction of the organic load in olive mill wastewater (OMW). In this study, removal of 95% of the phenolic compounds present in OMW was achieved using sand filtration and subsequent treatment with powdered activated carbon in a batch system. This pretreatment for OMW was found to enhance the anaerobic activity of the sludge in the batch system significantly. The efficiency of organic load removal achieved by the anaerobic treatment of untreated OMW in batch reactors with tap water dilution factors below 1:10, reached approximately 65% chemical oxygen demand (COD) removal. However, in the up-flow sludge anaerobic blanket (UASB) reactor, COD removal efficiency of 80–85% was reached at a hydraulic retention time (HRT) of 5 days with an influent COD concentration of 40 g l⁻¹ and organic loading rate (OLR)=8 g⁻¹ COD l⁻¹ per day.     

Organics and nitrogen removal and sludge stability in aerobic granular sludge membrane bioreactor

Novel aerobic granular sludge membrane bioreactor (GMBR) was established by combining aerobic granular sludge technology with membrane bioreactor (MBR). GMBR showed good organics removal and simultaneous nitrification and denitrification (SND) performances for synthesized wastewater. When influent total organic carbon (TOC) was 56.8-132.6 mg/L, the TOC removal of GMBR was 84.7-91.9%. When influent ammonia nitrogen was 28.1-38.4 mg/L, the ammonia nitrogen removal was 85.4-99.7%, and the total nitrogen removal was 41.7-78.4%. Moreover, batch experiments of sludge with different particle size demonstrated that: (1) flocculent sludge under aerobic condition almost have no denitrification capacity, (2) SND capacity was caused by the granular sludge, and (3) the denitrification rate and total nitrogen removal efficiency were enhanced with the increased particle size. In addition, study on the sludge morphology stability in GMBR showed that, although some granular sludge larger than 0.9 mm disaggregated at the beginning of operation, the granular sludge was able to maintain the stability of its granular morphology, and at the end of operation, the amount of granular sludge (larger than 0.18 mm) stabilized in GMBR was more than 56-62% of the total sludge concentration. The partial disaggregation of large granules is closely associated with the change of operating mode from sequencing batch reactor (SBR) system to MBR system.     

The inhibitory effects and removal of dieldrin in continuous upflow anaerobic sludge blanket reactors

The inhibitory effects and removal efficiency of dieldrin (DLD) in anaerobic reactors were investigated. Anaerobic toxicity assay (ATA) experiments conducted in batch reactors revealed that 30 mg/l DLD had inhibitory effects on the unacclimated mixed anaerobic cultures. Continuous reactor experiments performed in a lab-scale two-stage upflow anaerobic sludge blanket (UASB) reactor system which was fed with ethanol as the sole carbon source, indicated that anaerobic granular cultures could be successfully acclimated to DLD. Chemical oxygen demand (COD) removal efficiencies were 88-92% for the two-stage system. The influent DLD concentration of 10 mg/l was removed by 44-86% and 86-94% in the second stage and overall UASB system, respectively. Biosorption of DLD on granular anaerobic biomass was found to be a significant mechanism for DLD removal in the UASB system. The maximum DLD loading rate and minimum HRT achievable for the first stage UASB reactor were 0.5 mg/lday (76 microg DLD/g VSS.day) and 10 h, respectively, which resulted in the overall COD removal efficiency of 85%.     

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.     

生物膜法和SBR法相结合处理难降解制药废水的研究

采用生物膜法和SBR法相结合的废水处理工艺处理含抗生素类等难降解的制药废水 ,对生物膜的耐冲击负荷能力、生物膜对进水可生化性的影响、生物膜对好氧SBR活性污泥性能的影响、pH对系统去除效果的影响等工艺条件进行研究 ,并通过与传统SBR处理工艺的对比试验 ,进一步揭示了生物膜法和SBR法相结合的处理工艺强的耐冲击负荷能力。     

Comparative study of phenol and cyanide containing wastewater in CSTR and SBR activated sludge reactors

The objectives of this work were the examination of the performance of two bench scale activated sludge systems, a conventional Continuous Stirring Tank Reactor (CSTR) and a Sequential Batch Reactor (SBR), for the treatment of wastewaters containing phenol and cyanides and the assessment of the toxicity reduction potential by bioassays. The operation of the reactors was monitored by physicochemical analyses, while detoxification potential of the systems was monitored by two bioassays, the marine photobacterium Vibrio fischeri and the ciliate protozoan Tetrahymena thermophila. The reactors influent was highly toxic to both organisms, while activated sludge treatment resulted in the reduction of toxicity of the influent. An increased toxicity removal was observed in the SBR; however CSTR system presented a lower ability for toxicity reduction of influent. The performance of both systems was enhanced by the addition of powdered activated carbon in the aeration tank; activated carbon upgraded the performance of the systems due to the simultaneous biological removal of pollutants and to carbon adsorption process; almost negligible values of phenol and cyanides were measured in the effluents, while further toxicity reduction was observed in both systems.     

Capacities and limits of three different technologies for the biological treatment of leachate from solid waste landfill sites

Leachate from a municipal waste landfill site was treated using an activated sludge bioreactor, a fluidized bed biofilm reactor and a packed-bed column reactor (trickling filter). The leachate contained high organic matter (2.0–2.6 g/l of COD), high ammonium (300–700 mg/l) and sulphide (200–800 mg/l) concentrations, as well as low metal concentrations. The continuously operating reactors were employed to study the effects of TOC loading on the removal of TOC as well as on the nitrification and denitrification processes. Among the three biological treatment technologies investigated, the fluidized bed biofilm reactor was best with respect to removing ammonia and TOC. More than 90% of TOC and 99% of ammonia were removed when TOC loading was less than 0.5 kg/m³ × d. At a TOC loading of 4 kg/m³ × d, the removal of TOC and ammonia was 80% and 99%, respectively. In contrast, the treatment of leachate with the packed-bed reactor was successful in TOC removing only at TOC loading less than 0.3 kg/m³ × d (TOC elimination decreased from 86% at 0.06 kg/m³ × d to 60% at 0.3 kg/m³ × d). However, the reactor was active in nitrification even at a higher TOC loading (more than a 98% ammonia elimination at a TOC loading of 0.5 kg/m³ × d). Leachate was processed in the activated sludge reactor when TOC loading was less than 0.5 kg/m³ × d (with a removal of TOC and ammonia up to 83% and 99%, respectively). The activated sludge reactor was also effective in TOC removal at a higher TOC loading (e.g. a 74% TOC removal at a TOC loading of 1 kg/m³ × d), but for ammonia elimination, the activity continuously decreased (less than 60% ammonia removal at a TOC loading of 1 kg/m³ × d). Overloading in the activated sludge system was indicated by a high concentration of ammonia and nitrite in the effluent. In the packed bed reactor, overloading was characterized by a progressively incomplete TOC removal. No significant overloading was found in the fluidized bed reactor up to a TOC loading of 4 kg/m³ × d.     

Powdered activated carbon augmented activated sludge process for treatment of semi-aerobic landfill leachate using response surface methodology

This study was conducted to investigate aerobic biodegradation of semi-aerobic leachate with and without powdered activated carbon (PAC) addition. The experiment involved operating two 16L laboratory-scale activated sludge reactors in parallel at room temperature and adjusted to pH 6.5+/-0.5. One of the reactors was supplemented with PAC of 75-150microm size to observe its effect on semi-aerobic leachate biodegradation. Three hydraulic retention times (0.92, 1.57 and 2.22 d) and influent COD concentrations (750, 1800 and 2850mg/L) were applied in a factorial design for this study. The results showed enhanced reactor performance due to PAC addition with higher COD, colour and ammoniacal nitrogen removals. The PAC augmented reactor also had higher concentrations of NO(2)-N and NO(3)-N consequent of greater degree of nitrification.     

Effect of rhamnolipid on the aerobic removal of polyaromatic hydrocarbons (PAHs) and COD components from petrochemical wastewater

The removal efficiencies of 15 PAHs and some COD components (inert, readily degradable, slowly degradable and metabolic products) from a wastewater taken from a petrochemical industry treatment plant (İzmir, Turkey) have been determined using an aerobic completely stirred tank reactor (CSTR). Addition of rhamnolipid surfactant (15 mg l⁻¹) increased the removal efficiencies of PAHs and soluble COD from 72% and 90% to 80% and 99%, respectively. The rhamnolipid treatment caused a significant increase of 5- and 6-ring PAH degradation. The soluble COD removal efficiency was 93%, in CSTR reactors with rhamnolipid added. The inert COD removal efficiency was 60% in a CSTR reactor containing rhamnolipid. Batch tests showed that removal arising from the adsorption of the PAHs was low (between 1.88% and 4.84%) while the removal of PAHs from the petrochemical industry wastewater via volatilization varied between 0.69% and 5.92%. Low sorption capacity (K_p) values for refinery activated sludge (approximately 2.98 l g⁻¹) confirmed that bio-sorption was not an important mechanism controlling the fate of PAHs in aerobic CSTR reactors. Models proposed to simulate the PAH removal indicated that 94% of the PAHs were removed via biodegradation.     

Effect of hexavalent chromium on the activated sludge process and on the sludge protozoan community

The objectives of this study were the determination of chromium effects to the performance of an activated sludge unit and the investigation of the response of the activated sludge protozoan community to Cr(VI). Two bench scale activated sludge reactors were supplied with synthetic sewage containing Cr(VI), at concentrations from 1 up to 50 mg L(-1). Protozoan species were identified and were related to the system efficiency. Variations in the abundance and diversity of the protozoan species were observed under various chromium concentrations. High removal rates of organics and nutrients were observed after the acclimatization of the activated sludge, which were related to the initial chromium(VI) concentration. Chromium(VI) removal efficiency was high in all cases. The protistan community was affected by the influent chromium content. Dominance of sessile species was observed in the reactor receiving 5 mg L(-1) influent chromium, whereas co-dominance of sessile and carnivorous species was observed in the reactors receiving higher chromium concentrations.     

Rapid start-up and performance of denitrifying granular sludge in an upflow sludge blanket (USB) reactor treating high concentration nitrite wastewater

Denitrifying granular sludge reactor holds better nitrogen removal efficiency than other kinds of denitrifying reactors, while this reactor commonly needs seeding anaerobic granular sludge and longer period for start-up in practice, which restricted the application of denitrifying granular sludge reactor. This study presented a rapid and stable start-up method for denitrifying granular sludge. An upflow sludge blanket (USB) reactor with packings was established with flocculent activated sludge for treatment of high concentration nitrite wastewater. Results showed mature denitrifying granular sludge appeared only after 15 days with highest nitrogen removal rate of 5.844 kg N/(m³ day), which was much higher than that of compared anoxic sequencing batch reactor (ASBR). No significant nitrite inhibition occurred in USB and denitrification performance was mainly influenced by hydraulic retention time, influent C/N ratio and internal reflux ratio. Hydraulic shear force created by upflow fluid, shearing of gaseous products and stable microorganisms adhesion on the packings might be the reasons for rapid achievement of granular sludge. Compared to inoculated sludge and ASBR, remarkable microbial communitiy variations were detected in USB. The dominance of Proteobacteria and Bacteroidetes and enrichment of species Pseudomonas_stutzeri should be responsible for the excellent denitrification performance, which further verified the feasibility of start-up method.     

A modeling study of anaerobic biofilm systems: II. Reactor modeling

A rigorous steady-state model of anaerobic biofilm reactors taking into account acid-base and gas-phase equilibria in the reactor in conjunction with detailed chemical equilibria and mass transfer in acetate-utilizing methanogenic biofilms is presented. The performances of ideal completely stirred tank reactors (CSTRs) and plug-flow reactors, as well as reactors with nonideal hydraulic conditions, are simulated. Decreasing the surface loading rate increases the acetate removal efficiency, while decreasing the influent pH and increasing the buffering capacity improves the removal efficiency only if the bulk pH of the reactor shifts toward more optimal values between 6.8 to 7.0. The reactor can have negative or positive removal efficiencies depending on the start-up conditions. The respiration coefficient plays a critical role in determining the minimum influent pH required for reactor recovery after failure. Having multiple CSTRs-in-series generally increases the overall removal efficiency for the influent conditions investigated. Monitoring of the influent feed quality is critical for plug-flow reactors, becasue failure of the initial sections of the reactor may cause a cascading effect that may lead to a rapid reactor failure. (c) 1995 John Wiley & Sons, Inc.     

Stability of the ANAMMOX process in a gas-lift reactor and a SBR

In the last years, the ANAerobic AMMonium OXidation (ANAMMOX) process has been put forward as a promising alternative to treat ammonium rich wastewaters. An ANAMMOX gas-lift reactor and a sequential batch reactor (SBR) were operated during around 200 days in this study, reaching nitrogen loading rates (NLRs) of 2.0 and 0.75 g l(-1) per day, respectively. The efficiency in the nitrite (limiting substrate) removal was 99%. The ammonium and nitrite influent concentrations were increased stepwise until biomass in the reactors started to float. These flotation events coincided with periods when the NLR exceeded the maximum specific ANAMMOX activity (MSAA) of the sludge. The MSAA, determined in batch experiments, was 0.9 and 0.44 g g(-1) per day for biomasses from the gas-lift reactor and the SBR, respectively. Flotation of the biomass occurred most likely due to a granule density decrease caused by dinitrogen gas accumulation inside the granules and an apparent breakage of the granules. Further research is needed to understand this phenomenon and to optimise the corresponding strategies to counteract the flotation.     

High rate treatment of terephthalic acid production wastewater in a two-stage anaerobic bioreactor

The feasibility was studied of anaerobic treatment of wastewater generated during purified terephthalic acid (PTA) production in two-stage upflow anaerobic sludge blanket (UASB) reactor system. The artificial influent of the system contained the main organic substrates of PTA-wastewater: acetate, benzoate, and terephthalate. Three parallel operated reactors were used for the second stage, and seeded with a suspended terephthalate degrading culture, with and without additional methanogenic granular sludge (two different types). The first stage UASB-reactor was seeded with methanogenic granular sludge. Reactors were operated at 37 degrees C and pH 7. During the first 300 days of operation a clear distinction between the biomass grown in both reactor stages was obtained. In the first stage, acetate and benzoate were degraded at a volumetric loading rate of 40 g-COD/L . day at a COD-removal efficiency of 95% within the first 25 days of operation. No degradation of terephthalate was obtained in the first stage during the first 300 days of operation despite operation of the reactor at a decreased volumetric loading rate with acetate and benzoate of 9 g-COD/L . day from day 150. Batch incubation of biomass from the reactor with terephthalate showed that the lag-phase prior to terephthalate degradation remained largely unchanged, indicating that no net growth of terephthalate degrading biomass occurred in the first stage reactor. From day 300, however, terephthalate degradation was observed in the first stage, and the biomass in this reactor could successfully be enriched with terephthalate degrading biomass, resulting in terephthalate removal capacities of 15 g-COD/L . day. Even though no single reason could be identified why (suddenly) terephthalate degradation was obtained after such a long period of operation, it is suggested that the solid retention time as well the prevailing reactor concentrations acetate and benzoate may have played an important role. From day 1 of operation, terephthalate was degraded in the second stage. In presence of methanogenic granular biomass, high terephthalate removal capacities were obtained in these reactors (15 g-COD/L . day) after approximately 125 days of operation. From the results obtained it is concluded that terephthalate degradation is the bottleneck during anaerobic treatment of PTA-wastewater. Pre-removal of acetate and benzoate in staged bioreactor reduces the lag-phase prior to terephthalate degradation in latter stages, and enables high rate treatment of PTA-wastewater.     

A study on using fireclay as a biomass carrier in an activated sludge system

By adding a biomass carrier to an activated sludge system, the biomass concentration will increase, and subsequently the organic removal efficiency will be enhanced. In this study, the possibility of using excess sludge from ceramic and tile manufacturing plants as a biomass carrier was investigated. The aim of this study was to determine the effect of using fireclay as a biomass carrier on biomass concentration, organic removal and nitrification efficiency in an activated sludge system. Experiments were conducted by using a bench scale activated sludge system operating in batch and continuous modes. Artificial simulated wastewater was made by using recirculated water in a ceramic manufactutring plant. In the continuous mode, hydraulic detention time in the aeration reactor was 8 and 22 h. In the batch mode, aeration time was 8 and 16 h. Fireclay doses were 500, 1,400 and 2,250 mg l⁻¹, and were added to the reactors in each experiment separately. The reactor with added fireclay was called a Hybrid Biological Reactor (HBR). A reactor without added fireclay was used as a control. Efficiency parameters such as COD, MLVSS and nitrate were measured in the control and HBR reactors according to standard methods. The average concentration of biomass in the HBR reactor was greater than in the control reactor. The total biomass concentration in the HBR reactor (2.25 g l⁻¹ fireclay) in the continuous mode was 3,000 mg l⁻¹ and in the batch mode was 2,400 mg l⁻¹. The attached biomass concentration in the HBR reactor (2.25 g l⁻¹ fireclay) in the continuous mode was 1,500 mg l⁻¹ and in the batch mode was 980 mg l⁻¹. Efficiency for COD removal in the HBR and control reactor was 95 and 55%, respectively. In the HBR reactor, nitrification was enhanced, and the concentration of nitrate was increased by 80%. By increasing the fireclay dose, total and attached biomass was increased. By adding fireclay as a biomass carrier, the efficiency of an activated sludge system to treat wastewater from ceramic manufacturing plants was increased.     

渠式生物膜氧化法处理生活污水的技术研究

研究了利用渠式生物膜法进行生活污水处理实验。该法结合了活性污泥法和生物膜法的优点,能有效处理城市生活污水,而且装置不设二沉池,占地面积少,基建投资省。实验测定了不同的水力停留时间(HRT)和进水负荷下的化学需氧量(COD_Cr)及氨氮(NH₃-N)浓度,并分析其对去除率的影响。结果表明,在实验设定的范围内,COD_Cr和NH₃-N去除率随着水力停留时间的增大而增大,而随着进水负荷的增大而相应的减少。在水温25℃,流量0.6L·min^-1,COD_Cr 100mg·L^-1,NH₃-N 15 mg·L^-1的条件下,污染物的去除率较高(COD_Cr为71%、NH3-N为36%),出水水质比较理想,可以达到景观、娱乐和冷却水等的用水标准。     

Evaluation of sequencing batch reactor performance with aerated and unaerated FILL periods in treating phenol-containing wastewater

Performance of the sequencing batch reactor (SBR) treating synthetic phenolic wastewater at influent phenol concentrations from 100 to 1000 mg/L was evaluated. Two identical SBRs were built and operated with FILL, REACT, SETTLE and DRAW periods in the ratio of 4:6:1:1 for a cycle time of 12h. One of the reactors was operated with aerated FILL (R1) and the other with unaerated FILL (R2). The treated effluent quality and the rate of degradation during REACT were the criteria for evaluating performance of the two reactors. The results showed that the FILL mode had no significant influence on the treatment efficiency of phenol and COD for the entire range of influent phenol concentrations investigated. However, reactor R1 required a relatively shorter REACT time for phenol removal as compared to R2. This meant that R1 had the advantage of providing treatment at a higher organic loading rate.     

Denitrification of high nitrate wastewater in a cloth strip bioreactor with immobilized sludge

Denitrification of synthetic high nitrate wastewater containing 40,000?ppm NO₃ (9,032?ppm NO₃-N) was achieved using immobilized activated sludge in a column reactor. Active anoxic sludge adsorbed onto Terry cloth was used in the denitrification of high nitrate wastewater. The operational stability of the immobilized sludge system was studied both in a batch reactor and in a continuous reactor. The immobilized sludge showed complete degradation of different concentrations of NO₃-N (1,129, 1,693, 3,387, 6,774, and 9,032?ppm) in a batch process. The reactors were successfully run for 90?days without any loss in activity. The immobilized cell process has yielded promising results in attaining high denitrifying efficiency.     

Nitrification inhibition in landfill leachate treatment and impact of activated carbon addition

Leachate from a municipal landfill was combined with domestic wastewater and treated in batch, semi-continuously fed-batch (SCFB) and continuous-flow (CF) activated sludge systems with and without powdered activated carbon (PAC) addition. In the absence of PAC, nitrification was severely inhibited and nitrite accumulated to about 85–100% of the total NO_x-N. Addition of PAC to activated sludge reactors enhanced nitrification. In continuous-flow operation, nitrite accumulation could be completely prevented by PAC addition.