Anaerobic Sludge Bed Reactor Research Articles

Effect of 1,1,2,2-Tetrachloroethane on the Performance of Upflow Anaerobic Sludge Bed (UASB) Reactors

Chlorinated aliphatic hydrocarbons (CAH) are important environmental pollutants since they are industrially used for a wide variety of applications. Chlorinated hydrocarbons are cited as important contributors to the inhibition of anaerobic digestion. In this work, the effect of 1,1,2,2-tetrachloroethane (TCE) on the performance of upflow anaerobic sludge bed (UASB) reactors fed with sucrose synthetic wastewater has been studied. According to the results obtained it can be concluded the possibility to use UASB reactors with granular sludge to treat industrial wastewaters with a continuous content of TCE up to a concentration of 130 mg/l or with incidental punctual discharges of high concentration of the toxicant up to 400 mg/l. In all cases in which the activity of the reactor was inhibited a fast recuperation was observed.

Effect of 1,1,2,2-tetrachloro-ethane on the performance of upflow anaerobic sludge bed (UASB) reactors

Chlorinated aliphatic hydrocarbons (CAH) are important environmental pollutants since they are industrially used for a wide variety of applications. Chlorinated hydrocarbons are cited as important contributors to the inhibition of anaerobic digestion. In this work, the effect of 1,1,2,2-tetrachloroethane (TCE) on the performance of upflow anaerobic sludge bed (UASB) reactors fed with sucrose synthetic wastewater has been studied. According to the results obtained it can be concluded the possibility to use UASB reactors with granular sludge to treat industrial wastewaters with a continuous content of TCE up to a concentration of 130 mg/l or with incidental punctual discharges of high concentration of the toxicant up to 400 mg/l. In all cases in which the activity of the reactor was inhibited a fast recuperation was observed.

Full scale experience with tannery water management: An integrated approach

In this article, an overview is given of the proposed and actual activities that are undertaken to reduce the pollution from the approximately 180 tanneries in Kanpur, Uttar Pradesh, India. As a part of an action plan to reduce the pollution of the river Ganga, this project includes in-house measures to reduce the output of chromium by the tanneries, and pre-treatment at the tanneries to reduce the solids content of the wastewater and to facilitate maintenance of the sewer system. A treatment plant consisting of two Upflow Anaerobic Sludge Bed (UASB) reactors, followed by a post-treatment facility, reduces the wastewater pollution by approximately 80% of BOD, COD, and TSS. However, sulphide output is still high, owing to the high sulphate concentrations in the wastewater. The sludge produced during the operations is projected to be used as a fertilizer.

Development of anaerobic sludge bed (ASB) reactor technologies for domestic wastewater treatment: motives and perspectives.

During the treatment of raw domestic wastewater in the upflow anaerobic sludge blanket (UASB) reactor, the suspended solids (SS) present in the wastewater tend to influence negatively the methanogenic activity and the chemical oxygen demand (COD) conversion efficiency. These problems led to the emergence of various anaerobic sludge bed systems such as the expanded granular sludge bed (EGSB), the upflow anaerobic sludge blanket (UASB)-septic tank, the hydrolysis upflow sludge bed (HUSB), the two-stage reactor and the anaerobic hybrid (AH) reactor. However, these systems have, like the UASB reactor, limited performance with regard to complete treatment (e.g., removal of pathogens). In this respect, a new integrated approach for the anaerobic treatment of domestic wastewater is suggested. This approach combines a UASB reactor and a conventional completely stirred tank reactor (CSTR) for the treatment of the wastewater low in SS and sedimented primary sludge, respectively. The principal advantages of the proposed system are energy recovery from organic waste in an environmentally friendly way; lowering the negative effect of suspended solids in the UASB reactor; production of a high quality effluent for irrigation; and prevention of odour problems.

The effect of extreme temperatures (70–80°C) on the effluent quality and sludge characteristics of UASB reactors

The study focused on the effluent quality and sludge characteristics during the start-up and operation of extreme thermophilic (70 to 80°C) upflow anaerobic sludge bed (UASB) reactors, inoculated with mesophilic and thermophilic granular sludge and fed with acetate, volatile fatty acids (VFA), and thermomechanical pulping (TMP) whitewater. Low effluent quality and long start-up periods were observed during the start-up of the 70 to 76°C, VFA-fed UASB reactors inoculated with mesophilic granulae, while better effluent quality and considerably shorter start-up periods were observed when thermophilic (55/70°C) inocula were used. With VFA feed, a significant amount of acetate was removed at 70°C and even at 80°C, while propionate removal was negligible. With TMP whitewater feed, low VFA effluent concentration was obtained at 70°C. The volatile solids (VS) and the VS/total solids (TS) content of the sludge decreased significantly during the first 2–3 months of operation when mesophilic inocula were used. The initial specific methanogenic activity (ISMA) of the extreme thermophilic sludge decreased with increasing temperature and was slightly higher on glucose than on acetate. At 70 to 80°C, various rod-like bacteria were dispersed through the granulae in either individual or in low density micro colonies surrounded with a varying degree of precipitates.

Toxicity reduction and removal of dehydroabietic and abietic acids in a continuous anaerobic reactor

The inhibition of microorganisms in an upflow anaerobic sludge bed and filter reactor was evidenced by a sudden decrease in methane production, a decrease in the chemical oxygen demand elimination, and an increase in the acetate concentration of the treated effluent. The inhibition occurred after a cumulative loading of 3486 mg of resin acids (66% dehydroabietic acid and 34% abietic acid) on 10 g volatile suspended solids of an anaerobic granular sludge. The acetoclastic methanogens were the most inhibited group of bacteria following the reactor failure, while the activity of the hydrogenotrophic methanogens was not affected. During the phase of 9.5 mg/L/d of resin acid feeding, no resin acids were detected in the effluent; sorption of resin acids on the sludge amounted to 6.6 mg/g volatile suspended solids. During the feeding phase of 59 mg resin acids/L/d, the effluent showed an average resin acid concentration of 19 mg/L; the toxicity was half that of the influent (Microtox toxicity tests).

Pilot-scale thermophilic anaerobic treatment of wastewaters from seasonal vegetable processing industry

Thermophilic anaerobic treatment of food industry wastewaters was studied using a 0.65 m3 upflow anaerobic sludge bed (UASB) reactor. The reactor was operated at 55°C and placed on the premises of a factory manufacturing deep-frozen goods from vegetables. The hot (>80-90°C) and concentrated (COD 14-79 g/l) wastewater streams, deriving from steam peeling and blanching of carrot and potato were used. The UASB reactor was inoculated with a small amount of granular sludge from a full-scale mesophilic UASB reactor. Prior to inoculation, the inoculum was acclimated to 55°C for 2 days. The reactor was fed with a mixture of wastewaters diluted to the desired COD. The reactor was started with loading rates of about 1.2 kgCOD/m3d. After the initial acidification of the process, apparently due to insufficient buffer capacity, the COD removal started to improve and reached 60% within 35 days of inoculation. At the end of the 70 days run, more than 80% COD removal was achieved with loading rates of about 4 kgCOD/m3d. The pilot-study run was limited due to the end of the seasonal production in the target factory. The results of the pilot study together with the results from the intensive laboratory studies suggest the feasibility of thermophilic anaerobic treatment for the studied wastewaters.

Anaerobic pre-treatment of petrochemical effluents: Terephthalic acid wastewater

During petrochemical production of purified terephthalic acid (PTA, 1,4-benzene dicarboxylic acid), a large quantity of concentrated effluent is produced. Main polluting compounds in this wastewater are terephthalic acid, acetic acid and benzoic acid in decreasing order of concentration. Acetic acid and benzoic acid are known to be rapidly degraded in high rate anaerobic treatment systems, such as Upflow Anaerobic Sludge Bed (UASB) reactors. Concerning the kinetics of anaerobic mineralization of terephthalic acid, however, no information is available in literuature. Therefore our work focused on the anaerobic degradation of neutralized terephthalic acid (disodium terephthalate) in laboratory scale UASB-reactors and batch reactors. It was found that high rate anaerobic treatment of terephthalate was difficult to obtain due to the low growth rate (μ ≈ 0.04 day−1) of the terephthalate mineralizing mixed culture. The maximum removal capacity of a lab-scale UASB-reactor was found to be 3.9 g COD.1−1 .day−1 at a loading rate of 4.5 g COD.1−1 .day−1 and a hydraulic retention time of 24 hours. Terephthalate was used as sole carbon source during these experiments. Addition of small amounts of sucrose (co-substrate) to the influent, as a source of reducing equivalents, was found to have a negative influence on the anaerobic degradation of terephthalate. Also benzoate was found to inhibit the mineralization of terephthalate. Batch-toxicity experiments showed that terephthalate is not toxic to any of the species involved in its mineralization. Based on these observations, a staged anaerobic reactor system is suggested for the anaerobic pre-treatment of PTA-wastewater.

Economic impact of electrostatic precipitators pulse energization on dedusting in iron‐ore sintering plants

Investigates the application of the up‐flow anaerobic sludge bed (UASB) reactor for the anaerobic treatment of sewage sludge containing high concentrations of soluble and insoluble sulphides. Assesses the reactor’s performance in terms of volatile organic matter (VOM) and biogas production rate. The average percentage removal of VOM, total sulphide and biogas for the reactor operation without sulphide was 67 per cent, 65mgS/L and 1 L/day, respectively. The corresponding average percentage removal of VOM, total sulphide and biogas production rate for the experiment with 800mgS/L soluble sulphide was 45 per cent, 450mgS/L and 0.7L/day. Equilibrium concentrations of soluble sulphide up to 200mgS/L exert insignificant toxic effects, but toxicity increases as the concentration of soluble sulphide increases. A concentration of soluble sulphide of 1,200mgS/L produces severe toxic effects and the complete termination of gas production. An inhibitory concentration of sulphides affects gas production first, while significant volatile acid accumulation takes place much slower, and only after gas production has been severely retarded. Insoluble sulphide has an insignificant effect on the UASB up to a concentration of at least 800mgS/L. The addition of iron as ferric chloride prevents the toxicity of soluble sulphides as indicated by the minor effect on gas production. Therefore, the use of iron to precipitate sulphide could be used on a continuous basis to reduce sulphide toxicity.

The Effect of Sulphate on Propionate and Butyrate Degradation in a Psychrophilic Anaerobic Expanded Granular Sludge Bed (EGSB) Reactor

The effect of sulphate on the anaerobic psychrophilic degradation of propionate and butyrate was studied using an expanded granular sludge bed (EGSB) reactor. The EGSB reactor was operated at organic loading rates 7 – 12 kg COD·m-3·day-1, at hydraulic retention times of 2.5 – 1.6 h and at three different sulphate concentrations. The results of the continuous flow experiments and of batch experiments with sludge from the EGSB reactor reveal that the psychrophilic degradation of propionate is strongly affected by the presence of sulphate. Addition of 0.266 g SO4 2−-S·dm-3 to the medium resulted in a 35 % increase in the propionate conversion rate. In contrast, the butyrate degradation rate decreased by 32 % in the presence of sulphate. Syntrophic acetogenic butyrate-oxidizing consortia seem to compete effectively with sulphate reducing bacteria.

Biosorption of pentachlorophenol (PCP) by granular and dispersed anaerobic sludge

Abstract Anaerobic granular sludge from Upflow Anaerobic Sludge Bed (UASB) reactors contain a complete consortia of anaerobic microorganisms in an optimal spatial configuration. The importance of the spatial relationship of microbes in anaerobic granular sludge versus increased surface area (granules vs. free cells) as it pertains to biosorption and microbial toxicity is unknown. In this study, biosorption isotherms are reported for pentachlorophenol (PCP), using granular and dispersed anaerobic sludge from five different industrial sources. Pentachlorophenol biosorption data fit well to the Freundlich equation. There is no significant difference in biosorption capacity between dispersed and granular anaerobic sludge. Some variation in biosorption capacity is observed among the different industrial sources of sludge. Comparison with results reported by other investigators suggests that biosorption by anaerobic biomass is lower than that by aerobic microorganisms.

Hydrogen monitoring in anaerobic sludge bed reactors at various hydraulic regimes and loading rates

ABSTRACT: The dissolved hydrogen concentration was monitored in four laboratory‐scale upflow sludge bed reactors. The upflow velocity (υUP) differed in each reactor, providing different hydraulic regimes. Five pseudo‐steady‐state conditions were applied to the four reactors. The dissolved hydrogen concentration increased proportionally with the organic loading rates (OLR) of the reactors, to attain values as high as 20 μM, while still remaining independent of the hydraulic regime. The experimental data yielded low hydrogen mass‐transfer rates (kLa) and high ratios of the measured dissolved hydrogen concentration value to the equilibrium value calculated from the hydrogen partial pressure in the gas phase (sursaturation factor): from 0.04 to 0.46 h−1 and from 19 to 102, respectively. Also, the increase in the υUP did not affect the hydrogen kLa nor the sursaturation factor. The kLa values showed a reasonable and positive correlation with the OLR values and the gasflow rates, however no correlation was found between the sursaturation actor values and the latter parameters. This indicates that dissolved hydrogen concentration can not be predicted from hydrogen gaseous measurements in such reactors.

Waste Water Management in a Sugar Beet Factory: A Case Study of Comparison between Anaerobic Technologies

The ACOR-l sugarbeet factory owns a waste water treatment plant which handles 2500 m3/d of medium strength wastewater (COD = 4000 mg/L). The system was designed to treat the excess wastewater from the beet transport circuit, some process streams, the sanitary waters and wastewaters from an alcohol distillery. The plant is based on two lagoons for equalization and pre-acidification of the waste, an Upflow Anaerobic Sludge Bed (UASB) reactor (efficiency > 97% soluble COD) and a small lagoon used for final polishing of the effluent. A pilot-scale Fluidized Bed (FB) reactor was run in parallel with the UASB reactor to assess the capability of the FB system. There were two runs in consecutive campaigns, where results showed very good efficiency in spite of very high loading rates and low hydraulic residence times achieved in the FB system.

A Comparison of Anaerobic Reactors Operating With and Without the Addition of Sulfates

Abstract Three pairs of anaerobic upflow sludge bed reactors were compared. Each pair received the same amount of whey and waste sulfite liquor. Sulfate loaded gas-stripped reactor R4 performed as well as its methanogenic (no addition of sulfates) counterpart R6. The performance of unstripped sulfate-loaded reactors R1 and R3 was comparable to the gas-stripped R2 and R4 only when reactor loads were below 3 kg COD/m3·d and 0.5 kg S/m3·d. At higher loads the performance deteriorated significantly. Syntrophic generation of methane and sulfides was found to be the prerequisite to attaining high removals of COD.

Methane production from acidic waste streams without addition of neutralizing chemicals

Abstract An Upflow Anaerobic Sludge Bed (UASB) reactor was used to produce methane from the product of batch‐wise liquefaction/acidogenesis of waste tomatoes. Although the influent had a pH in the range 3.2 ‐ 4.2, it was possible to operate the UASB reactor at loading rates as high as 22 kg COD/(m3.day), without the need of adding neutralizing chemicals. Treatment efficiencies of approximately 90 % (with over 80 % of the influent COD converted into methane) were obtained. During stable operation the pH in the reactor was in the range 7.1 ‐ 7.3. The pH dropped to 6.85 at a 10 % overloading. The mechanism of pH auto‐control in anaerobic digestion of acidic waste streams is discussed.