Combined System for Biological Removal of Nitrogen and Carbon from a Fish Cannery Wastewater

A combined system composed of three sequentially arranged reactors, anaerobic-anoxic-aerobic reactors, was used to treat the wastewater generated in the tuna cookers of a fish canning factory. These wastewaters are characterized by high chemical oxygen demand (COD) and nitrogen concentrations. The anaerobic process was performed in an upflow anaerobic sludge blanket reactor operated in two steps. During Step I different influent COD concentrations were applied and organic loading rates (OLRs) up to 4 g COD/(L?d) were achieved. During Step II hydraulic retention time (HRT) was varied from 0.5 to 0.8 days while COD concentration in the influent was constant at 6 g COD/L. The OLRs treated were up to 15 g COD/(L?d). When HRTs longer than 0.8 days were used, COD removal percentages of 60% were obtained and these values decreased to 40% for a HRT of 0.5 days. The denitrification process carried out in an upflow anoxic filter was clearly influenced by the amount of carbon source supplied. When available carbon was present, the necessary COD/N ratio for complete denitrification was around 4 and denitrification percentages of 80% were obtained. The nitrification process was successful and was almost unaffected by the presence of organic carbon (0.2–0.8 g TOC/L), with ammonia removal percentages of 100%. Three recycling ratios (R/F) between the denitrification and nitrification reactors were applied at 1, 2, and 2.5. The overall balance of the combined system indicated that COD and N removal percentages of 90% and up to 60%, respectively, were achieved when the R/F ratio was between 2 and 2.5.     

Anaerobic Degradation of Sulfate Laden Organics Employing Different Reactor System Configurations

Anaerobic degradation of sulfate laden organics has been investigated employing bench-scale models of an upflow anaerobic sludge blanket (UASB) reactor, anaerobic baffled reactor (ABR), and hybrid ABR (HABR). Results indicated chemical oxygen demand (COD) removal over 65% in all three systems at a COD/SO42? ratio of 8.57–8.59. However, the performance deteriorated at a low COD/SO42? ratio of 6.92–7.05 with a reduction in COD removal to 41–55%. Supplementation of limiting nutrients improved COD removal ( ≈ 94.5%) in an UASB system and indicated nutrient deficiency as a primary cause of poor performance. However, poor COD removal (45.92–56.12%) in ABR and HABR indicated a severe inhibition of microbial consortia by sulfide. This study revealed that system configuration aggravated the problem of sulfide toxicity due to sequential phase separation in ABR and HABR systems at low dissolved sulfide concentration relative to the UASB reactor, a single-phase system. Sulfate removal was over 88% in all three systems.     

Combined Removal of Carbon and Nitrogen in an Integrated UASB-Jet Loop Reactor Bioreactor System

An innovative anaerobic–aerobic integrated bioreactor system consisting of an upflow anaerobic sludge blanket (UASB) and a jet loop reactor was developed to investigate the feasibility of combined removal of carbon and nitrogen for a low-strength wastewater at different hydraulic retention times (HRTs) and recycle ratios. Total chemical oxygen demand (COD) removal of the integrated system increased from 87 to 92%, at a combined system HRT of 44?h, when the recycle ratio was increased from 100 to 400%, respectively. Denitrification efficiency of the integrated system increased from 49 to 86%, at all HRTs, when the recycle ratio was increased from 100 to 400%. The integrated system, on average, achieved more than 78% of total nitrogen at all HRTs. Nitrogen content of the biogas produced from the UASB reactor increased with increase in recycle ratios while the methane content exhibited a reverse trend, irrespective of the HRTs. Sludge volume index of the UASB reactor increased from 15?to?42?mL/g total suspended solids at the end of the study. Specific methanogenic activity of the granular sludge decreased from 1.3 to 0.8 g CH4–COD/g volatile suspended solids per day at the end of the study. Nitrogen and COD mass balance of the integrated system indicated that a substantial amount of influent nitrogen and COD was lost in the effluent as dissolved form.     

Effects of Stressed Loading on Startup and Granulation in Upflow Anaerobic Sludge Blanket Reactors

The successful operation of an upflow anaerobic sludge blanket (UASB) process depends on the formation of settleable and active granular sludge. As the anaerobic bacteria are slow-growing microorganisms, a common problem encountered in UASB operation is the long startup period and the development of biogranules. In the present study, an unconventional approach to accelerate startup and granulation processes in UASB reactors has been developed by stressing the organic loading rate (OLR) without having to reach steady-state conditions. Three UASB reactors treating a synthetic feed with chemical oxygen demand (COD) of 2,500 mg/L, at a mesophilic temprature of 35°C were studied. One reactor (R1) served as a control, while the other two (R2 and R3) were operated at different stress levels upon reaching COD removal efficiency of 75 and 85%, respectively. Experimental results indicated that under stressed loading conditions, the startup, and granule development were accelerated by 45 and 33%, respectively, along with the formation of granules of superior characteristics without deteriorating loading capacity. The operating time to reach designated OLRs was also shortened by at least 30 days in the stressed reactors. The results presented indicate that the unconventional startup approach could offer a practical solution for the inherent long start-up in UASB systems with concomitant saving in time and cost.     

Combined Anaerobic/Aerobic Secondary Municipal Wastewater Treatment: Pilot-Plant Demonstration of the UASB/Aerobic Solids Contact System

Anaerobic pretreatment followed by aerobic posttreatment of municipal wastewater is being used more frequently. Recent investigations in this field using an anaerobic fluidized bed reactor/aerobic solids contact combination demonstrated the technical feasibility of this process. The investigation presented herein describes the use of a combined upflow anaerobic sludge bed (UASB)/aerobic solids contact system for the treatment of municipal wastewater and attempts to demonstrate the technical feasibility of using the UASB process as both a pretreatment unit and a waste activated sludge digestion system. The results indicate that the UASB reactor has a total chemical oxygen demand removal efficiency of 34%, and a total suspended solids removal efficiency of about 36%. Of the solids removed by the unit, 33% were degraded by the action of microorganisms, and 4.6% accumulated in the reactor. This low solids accumulation rate allowed operating the UASB reactor for three months without sludge wasting. The long solids retention time in this unit is comparable to the one normally used in conventional sludge digestion units, thus allowing the stabilization of the waste activated sludge returned to the UASB reactor. Particle flocculation was very poor in the UASB reactor, and therefore, it required postaeration periods of at least 100?min to proceed successfully in the aerobic unit. Polymer generation, which is necessary for efficient biological flocculation, was practically nonexistent in the anaerobic unit; therefore, it was necessary to maintain dissolved oxygen levels greater than 1.5?mg/L in the aerobic solids contact chamber for polymer generation to proceed at optimum levels. Once these conditions were attained, the quality of the settled solids contact chamber effluent always met the 30?mg BOD/L, 30?mg SS/L secondary effluent guidelines.     

Biological treatment of dye wastewaters using an anaerobic-oxic system

Three dye solutions, namely, C.I. Acid Yellow 17, C.I. Basic Blue 3, and C.I. Basic Red 2, were treated in an upflow anaerobic sludge blanket (UASB) reactor followed by a semi-continuous aerobic activated sludge tank. When hydraulic retention time was about 12 hours, no significant color removal was observed in the aerobic stage. In the anaerobic stage, Acid Yellow 17, Basic Blue 3, and Basic Red 2 were removed by 20%, 72%, and 78%, respectively. To treat wastewater from a dye manufacturing factor with COD concentration of 1200 mg/l and Color of 500 degrees (dilution factor), an UASB reactor (4.5 liters) and an activated sludge tank (5 liters, adjustable), COD and color were removed by more than 83% and 90% at a COD loading rate of 5.3 kg COD/m3-day in the anaerobic stage, and at the hydraulic retention time of 6-10 hours for the anaerobic stage and 6.5 for the aerobic stage. The anaerobic stage of the A/O system removes both color and COD. In addition, it also improves biodegradability of dyes for further aeroic treatment.     

Biodegradation of Mixtures of Phenolic Compounds in an Upward-Flow Anaerobic Sludge Blanket Reactor

The anaerobic biodegradability of mixtures of phenolic compounds was studied under continuous and batch systems. Continuous experiments were carried out in up-flow anaerobic sludge bed (UASB) reactors degrading a mixture of phenol and p-cresol as the main carbon and energy sources. The total chemical oxygen demand (COD) removal above 90% was achieved even at organic loading rates as high as 7 kg COD/m3/day. Batch experiments were conducted with mixtures of phenolic compounds (phenol, p-cresol, and o-cresol) to determine the specific biodegradation rates using unadapted and adapted anaerobic granular sludge. Phenol and p-cresol were mineralized by adapted sludge with rates several orders of magnitude higher than unadapted sludge. Additionally, an UASB reactor was operated with the mixture phenol, p-cresol, and o-cresol. After 54 days of operation, 80% of o-cresol (supplied at 132 mg/L) was eliminated. The phenol biodegradation was not affected by the presence of o-cresol. These results demonstrate that major phenolic components in petrochemical effluents can be biodegraded simultaneously during anaerobic treatment.     

Evaluation of Influent Medium Composition and Concentration in a Batch Reactor for Effective Startup of UASB Reactors

This study demonstrated the use of batch bioreactor experiments as an evaluation tool to determine appropriate influent medium composition and concentration for effective startup of an upflow anaerobic sludge blanket (UASB) reactor. Using seed sludge from a domestic treatment plant, the weight ratio of glucose and volatile fatty acids (VFA) present in the influent synthetic medium was varied and the batch performance was assessed in terms of pH variation during the course of the experiment, chemical oxygen demand (COD) reduction, specific substrate uptake rates, methanogenic activity, and methane yield. The performance was also evaluated by increasing the concentration of influent COD. Medium composition with glucose to VFA weight ratio at or below 2:8 and COD concentration at 11?g/L was determined to be optimum for effective startup of the UASB reactors. Utilization of the optimized influent medium provided a pH variation from 6.5 to 7.8 over the length of the UASB reactor and resulted in granule formation, high methanogenic activity, and methane yield. The evaluation method provided a practical approach to determine the applicability of seed sludge from a particular source and the desired influent characteristics for reduced startup duration in UASB processes.     

UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.     

Effect of Aeration on the Quality of Effluent from UASB Reactor Treating Sewage

The treatment of effluent of pilot- and full-scale upflow anaerobic sludge blanket (UASB) reactors operating at steady state was studied in an aeration-settling system. The fine pore submerged diffusers were used to aerate the effluent of UASB reactors under different operating conditions. Forty to 55% of the biochemical oxygen demand (BOD) and the chemical oxygen demand (COD) removal efficiencies were achieved by the direct aeration of the UASB effluent in the laboratory. The maximum removal efficiencies were achieved at 30?min hydraulic retention time (HRT) and a dissolved oxygen (DO) of 5–6??mg/L or high KLa (vigorous aeration). Batch experiments on nitrogen purging and the aeration of sulfides, volatile organic compounds (VOCs), and nonpurgeable organic carbons (NPOCs) were performed to ascertain the mechanism of BOD/COD removal. During aeration, BOD and COD were reduced by the stripping of H2S and VOCs and by the chemical oxidation of total sulfides and organic carbon. The stripping and chemical oxidation depended on the HRT and DO. The performance of a full-scale surface aeration system was compared to the performance of a pilot-scale diffused aeration system. Final sedimentation was effective only in removing the solids from the effluent of the aeration system. The results were confirmed by organic mass balance.     

Treatment of High-Strength Pharmaceutical Wastewater and Removal of Antibiotics in Anaerobic and Aerobic Biological Treatment Processes

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.     

Activated Carbon Addition to a Submerged Anaerobic Membrane Bioreactor: Effect on Performance, Transmembrane Pressure, and Flux

This study examined the effect of the addition of activated carbon to three, 3 L submerged anaerobic membrane bioreactors (SAMBRs) in terms of chemical oxygen demand (COD) removal, flux, and transmembrane pressure (TMP). The feed was a synthetic substrate with a COD of 460?mg?L?1, with one reactor run as a control, one with 1.7?g?L?1 of powdered activated carbon (PAC), and the third with 1.7?g?L?1 of granular activated carbon (GAC). While COD removal was high in all reactors (>90%), in comparison to the control (SAMBR1), the average COD removal in SAMBR2 (PAC) increased by 22.4%, while SAMBR3 with GAC was not significantly better. Because PAC has a significantly greater surface area per mass than GAC, it is probable that this difference was primarily due to the greater absorbance of fine colloidal particles and high molecular weight organics onto the carbon surface. These effects manifested themselves by SAMBR2 having lower TMPs and higher fluxes than both SAMBR3 and SAMBR1. Volatile fatty acids in the effluent from all three SAMBRs were extremely low (<18?mg?L?1), even during step changes in hydraulic retention tune, and most of the soluble COD in the effluent was soluble microbial products. Biochemical methane potential assays showed that biomass in the SAMBRs was less active than the seed sludge, and it appears that the addition of activated carbon to Reactors SAMBR2 and SAMBR3 provided a solid support for growth, and hence reduced floc breakage.     

Biotransformation of Carbon Tetrachloride and Anaerobic Granulation in a Upflow Anaerobic Sludge Blanket Reactor

Carbon tetrachloride (CT) in a synthetic wastewater was effectively degraded in a 2?l upflow anaerobic sludge blanket reactor during the granulation process by increasing the chemical oxygen demand (COD) and CT loadings. The effect of operational parameters such as influent CT concentrations, COD, CT loading, food to mass (F/M) ratio, and specific methanogenic activity (SMA) were also detected during granulation. Over 97% of CT was removed at 37°C, at a COD loading rate of 10?g/L?day. Chemical oxygen demand and CT removal efficiencies of 92 and 88% were achieved when the reactor was operating at CT and COD loading rates of 17.5?mg/L?day and 12.5?g/L?day, respectively. This corresponds to an hydraulic retention time of 0.28?day and an F/M ratio of 0.57?g?COD/g?volatile?suspended?solids?(VSS)?day. In 4?weeks, the seed sludge developed the CT degrading capability that was not very sensitive to shocks. The granular sludge cultivated had a maximum diameter of 2.5?mm and SMA of 1.64?g?COD/g?VSS?day. Glucose biodegradation by CT acclimated anaerobic granules was expressed with competitive inhibition. However the competitive inhibition was not significant since the competitive inhibition coefficient (Ki) was as high as 18.72?mg/L. Kinetic coefficients of k (maximum specific substrate utilization rate), Ks (half velocity coefficient), Y (growth yield coefficient), and b (decay coefficient) were determined as 0.6/day, 1.1?mg/L, 0.23?g?VSS/g glucose-COD, and 0.01/day, respectively, based on growth substrate glucose–COD during CT biotransformation. The CT was treated via biodegradation and this contributed to 89% of the total removal. The removal contributions from biomass adsorption, abiotic transformation, and volatilization were negligible. Adsorption and volatilization accounted for only 0.8 and 0.5% of the total removal, respectively.     

Molecular Mechanism of Granulation. II: Proton Translocating Activity

A laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used in this study to produce granular sludge at mesophilic temperatures (35 ± 1°C). After more than 150 days of operation, a COD removal efficiency of 95% was achieved with an organic loading rate of 8.73 gCOD∕L∕day. At the same time, the sludge granulation process was observed. The mature granules were examined for their stability in terms of the presence of calcium ion, surfactant, pH (buffer and H2SO4∕NaOH solution), metabolic inhibitor (iodoacetic acid and sodium fluoride), and proton translocator (carbonyl cyanide m-chlorophenyl-hydrazone). The results showed that bacterial surface dehydration, biological metabolic activity, and proton translocating activity were directly related to the strength of UASB granules. This indicated that the proton translocating activity on bacterial surfaces was the crucial factor in sludge granulation and, as a consequence, supported the proton translocation-dehydration theory. Experimental results from other studies were also used to support this new theory.     

Treatment of Landfill Leachate by a Combined Anaerobic Fluidized Bed and Zeolite Column System

The use of a combined anaerobic fluidized bed and zeolite fixed bed system in sanitary landfill leachate treatment was investigated. Anaerobic treatability studies were successfully performed in the anaerobic fluidized bed reactor. The chemical oxygen demand (COD) removal was attained up to 90% with increasing organic loading rates as high as 18?g?COD/L?day after 80?days of operation. Good biogas production yield (Ygas) of 0.53?L biogas per gram removed COD with methane (CH4) content of 75% was obtained. The attached biomass concentration increased along the column height from bottom to top, and its mean value was found 6,065?mg/L after 100?days of operation. The anaerobically treated landfill leachate was further treated by a zeolite fixed bed reactor. While excellent ammonia removal (>90%) was obtained with the untreated zeolite, the regenerated zeolites showed higher performance. Consequently, this combined anaerobic and adsorption system is an effective tool to remove high COD and high ammonia in landfill leachate.     

2,4,6 Tri-Chlorophenol Containing Wastewater Treatment Using a Hybrid-Loop Bioreactor System

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with an effluent recycle was used for biological treatment of 2,4,6 tri-chlorophenol (TCP) containing synthetic wastewater. The effects of sludge age (solids retention time) on chemical oxygen demand (COD), TCP, and toxicity removal performance of the system were investigated for sludge ages between 5 and 30?days, while the feed COD (2600±100?mg?L?1), TCP (370±10?mg?L?1), and the hydraulic residence time (25?h) were constant. Percent TCP, COD, and toxicity removals increased with increasing sludge age resulting in nearly complete COD, TCP, and toxicity removal at sludge ages above 20?days. Biomass concentrations in the packed column and in the aeration tank increased with increasing sludge age resulting in low reactor TCP concentrations, and therefore, high TCP, COD, and toxicity removals. More than 95% of COD, TCP, and toxicity removal took place in the packed column reactor. Volumetric rates of TCP and COD removal increased due to increasing biomass and decreasing effluent TCP and COD concentrations with increasing sludge age. The specific rate of TCP removal was maximum (120?mg?TCP?gX?1?day?1) at a sludge age of 20?days. TCP inhibition was eliminated by operation of the system at sludge age above 20?days to obtain nearly complete COD, TCP, and toxicity removal.     

Fate of Anionic Surfactants in a 38?ML/Day UASB-Based Municipal Wastewater Treatment Plant: Case Study

The outcome of a 15-month monitoring study (August 2004–October 2005) on the anionic surfactants (AS), at the 38?ML/day up-flow anaerobic sludge blanket (UASB)-based sewage treatment plant (STP) is described. The average removal of AS was only around 57%. Appreciable concentration of AS was being discharged to the watercourse (average 2.41?mg/L; range 0.63–5.16?mg/L). On an average dried sludge contained 1,560?mg?AS?kg?1 dry weight. Mass balance indicated that, AS load of the orders of 23 and 33% is removed by adsorption in UASB reactors and polishing ponds (PP), respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation ( ≈ 70%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100?units, than 43 and 7?units are discharged with treated effluent and dried sludge, respectively, whereas 33 and 16?units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds, respectively.     

Effect of an Organic Shock Load on the Stability of an Anaerobic Migrating Blanket Reactor

The goal of this study was to examine the effect of an organic shock load on the performance and stability of a laboratory-scale anaerobic migrating blanket reactor (AMBR). To accomplish an organic shock load, nonacidified sucrose solution was almost doubled in concentration, while maintaining a constant hydraulic retention time. The volumetric loading rate (VLR) was increased from 27 to 50 g chemical oxygen demand (COD) L?1?day?1 for a period of six hydraulic retention times (42 h). This resulted in an increase in the standard methane production rate (liters of methane at standard temperature and pressure per liter reactor volume per day) from 7 to 12 L?L?1?day?1. The pH levels stayed favorable and biomass washout was limited during the shock load due to the damping effects of a compartmentalized configuration. During the shock load, the propionate production in the initial compartments of the AMBR remained at the same level as before the shock load, while the acetate production rose sharply. Because propionate is the most difficult volatile fatty acid to be removed, unstable conditions due to excessive propionate accumulation during the shock load were prevented. Meanwhile, the acetate concentration in the liquid phase and hydrogen content in the headspace of the final compartments remained low, which ensured propionate degradation. Due to these intrinsic characteristics of the AMBR, the soluble COD removal efficiency stayed above 87% under these stressed conditions. Moreover, the performance of the AMBR reached pre-shock-load levels immediately after the VLR was restored to 25 g?COD?L?1?day?1.     

Biodegradation of Phenol with Wastewater as a Cosubstrate in Upflow Anaerobic Sludge Blanket

Anaerobic degradation of phenol mixed with a readily degradable synthetic wastewater (DSWW) as a cosubstrate was studied in a 12?L upflow anaerobic sludge blanket reactor at 30±2°C over a period of 632?days. DSWW was prepared by diluting sugar cane based molasses. The biomass was acclimatized to high phenol concentration by gradually decreasing the DSWW chemical oxygen demand (COD) of 4,000?mg/L. Feed made up of phenol COD and DSWW COD in the ratio of 7:3 (phenol concentration = 1,176?mg/L) was successfully treated at a hydraulic retention time (HRT) of 12?h and organic loading rate (OLR) of 8?g?COD/L?day. Phenol removal ranged from 99.9 to 84% at phenol COD varying from 10 to 70% in the feed. During the entire operation, COD removal varied from about 74 to 91.3%. The influent COD was distributed into CH4–COD ( ～ 72%), effluent COD ( ～ 17%), and sludge and unaccounted COD ( ～ 11%). The process failure occurred at 4:1 phenol COD: DSWW COD. Specific methanogenic activity of granular sludge exhibited uniform activity up to phenol COD of 70%. The performance of the reactor could not be maintained beyond 70% phenol COD even by reducing the sludge loading rate, increasing HRT, or decreasing OLR.