Treatment of low strength complex wastewater using an anaerobic baffled reactor (ABR)

Treatment of a low strength complex wastewater of chemical oxygen demand (COD) around 500mg/L was studied in a 10L capacity laboratory scale anaerobic baffled reactor (ABR). It was operated at hydraulic retention times (HRTs) of 20, 15, 10, 8 and 6h. Corresponding organic loading rates (OLRs) were 0.6, 0.8, 1.2, 1.5 and 2kg COD/m(3)d. At every HRT (or OLR), pseudo steady state (PSS) was achieved. Even at maximum OLR of 2kg COD/m(3)d, COD and biochemical oxygen demand (BOD) removals exceeded 88%. Removal of particulate fraction of organics was found to be greater than soluble fraction. Compartment-wise studies of various parameters revealed that if the OLR was larger, the number of initial compartments played significant role in the removal of organics. The values of volatile fatty acids (VFA) demonstrated that hydrolysis and acidogenesis were the main biochemical activities in the initial few compartments. Based on the tracer studies, dead space in the ABR was found to range from 23% to 34%. The flow pattern in the ABR was classified as intermediate between plug flow and perfectly mixed flows. Observations from scanning electron micrographs (SEM) also suggested that distinct phase separation takes place in an ABR. Study of organic and hydraulic shock loads revealed that ABR was capable of sustaining the type of shock loads generally experienced at a sewage treatment plant (STP).     

Ambient temperature treatment of low strength wastewater using anaerobic sequencing batch reactor

Low strength wastewater having chemical oxygen demands (COD) concentrations of 1000, 800, 600 and 400mg/l were treated at 35, 25, 20 and 15¡C using four anaerobic sequencing batch reactors (ASBRs). Reactor 1 was operated at hydraulic retention time (HRT) of 48h, reactor 2 at 24h HRT, reactor 3 at 16h HRT and reactor 4 at 12h HRT. 80 to 99% soluble COD was removed at the various operational conditions, except during 15¡C treatment of 1000 and 800mg/l COD wastewater at 12h HRT and 1000mg/l COD wastewater at 16h HRT, where excessive loss of biological solids occurred. The ASBR process can be an effective process for the treatment of low concentrated wastewaters which are usually treated aerobically with large amount of sludge production and higher energy expenditures.     

Treatment of domestic wastewater in an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor

The performance of a laboratory-scale sewage treatment system composed of an up-flow anaerobic sludge blanket (UASB) reactor and a moving bed biofilm reactor (MBBR) at a temperature of (22–35 °C) was evaluated. The entire treatment system was operated at different hydraulic retention times (HRT’s) of 13.3, 10 and 5.0 h. An overall reduction of 80–86% for COD_total; 51–73% for COD_colloidal and 20–55% for COD_soluble was found at a total HRT of 5–10 h, respectively. By prolonging the HRT to 13.3 h, the removal efficiencies of COD_total, COD_colloidal and COD_soluble increased up to 92, 89 and 80%, respectively. However, the removal efficiency of COD_suspended in the combined system remained unaffected when increasing the total HRT from 5 to 10 h and from 10 to 13.3 h. This indicates that, the removal of COD_suspended was independent on the imposed HRT. Ammonia-nitrogen removal in MBBR treating UASB reactor effluent was significantly influenced by organic loading rate (OLR). 62% of ammonia was eliminated at OLR of 4.6 g COD m⁻² day⁻¹. The removal efficiency was decreased by a value of 34 and 43% at a higher OLR’s of 7.4 and 17.8 g COD m⁻² day⁻¹, respectively. The mean overall residual counts of faecal coliform in the final effluent were 8.9 × 10⁴ MPN per 100 ml at a HRT of 13.3 h, 4.9 × 10⁵ MPN per 100 ml at a HRT of 10 h and 9.4 × 10⁵ MPN per 100 ml at a HRT of 5.0 h, corresponding to overall log₁₀ reduction of 2.3, 1.4 and 0.7, respectively. The discharged sludge from UASB–MBBR exerts an excellent settling property. Moreover, the mean value of the net sludge yield was only 6% in UASB reactor and 7% in the MBBR of the total influent COD at a total HRT of 13.3 h. Accordingly, the use of the combined UASB–MBBR system for sewage treatment is recommended at a total HRT of 13.3 h.     

Evaluation of inverse anaerobic fluidized bed reactor for treating high strength organic wastewater

The aim of this work is to evaluate the feasibility of an inverse fluidized bed reactor for the anaerobic digestion of distillery effluent, with a carrier material that allows low energy requirements for fluidization, providing also a good surface for biomass attachment and development. Inverse fluidization particles having specific gravity less than one are carried out in the reactor. The carrier particles chosen for this study was perlite having specific surface area of 7.010 m2/g and low energy requirements for fluidization. Before starting up the reactor, physical properties of the carrier material were determined. One millimeter diameter perlite particle is found to have a wet specific density of 295 kg/m3. It was used for the treatment of distillery waste and performance studies were carried out for 65 days. Once the down flow anaerobic fluidized bed system reached the steady state, the organic load was increased step wise by reducing hydraulic retention time (HRT) from 2 days to 0.19 day, while maintaining the constant feed of chemical oxygen demand (COD) concentration. Most particles have been covered with a thin biofilm of uniform thickness. This system achieved 84% COD removal at an organic loading rate (OLR) of 35 kg COD/m3/d.     

Performance of a periodic anaerobic baffled reactor fed on Chinese traditional medicine industrial wastewater

A four-compartment periodic anaerobic baffled reactor (PABR) was run in a 'clockwise sequential' switching manner continuously fed on chinese traditional medicine industrial wastewater under an alkalinity concentration between 1000 and 1500 mg CaCO(3)/L of the feed with average organic load rate (OLR) at about 1, 2, 4 and 6 kg COD/(m(3)d) for 12, 24, 24 and 6d, respectively. Hydraulic residence time was 2d, while switching period was 4d. As the average OLR increased to 6 kg COD/(m(3)d), the time of the sharp fall in pH, chemical oxygen demand (COD) removal, gas production and methane percentage of the biogas of all the compartments and the time of rapid volatile fatty acids accumulation in effluent coincided, hence the PABR became sour. Denaturing gradient gel electrophoresis (DGGE) community fingerprints and their cluster analysis revealed that community structures of each compartment tended to be more closely related if the PABR was not overloaded.     

Treatment of poultry slaughterhouse wastewater in hybrid upflow anaerobic sludge blanket reactor packed with pleated poly vinyl chloride rings

In this study, the performance of 5.4 L hybrid upflow anaerobic sludge blanket (HUASB) reactor for treating poultry slaughterhouse wastewater under mesophilic conditions (29-35 °C), was investigated. After starting-up, the reactor was loaded up to an OLR of 19 kg COD/m³ d and achieved varied TCOD and SCOD removal efficiencies of 70-86% and 80-92%, respectively. The biogas was varied between 1.1 and 5.2 m³/m³ d with the maximum methane content of 72%. The maximum methane yield was 0.32 m³/kg COD_removed at an OLR of 9.27 kg COD/m³ d. Black matured granules of size between 2.5 and 5 mm were observed at the end of 225 d operation. RTD study showed the flow behavior was in mixed regime at the end of performance study. Step wise polynomial regression analysis was fitted well. Methanobacterium and Methanosaeta bacteria were dominant at the end of start-up whereas Methanosarcina, Cocci and rods were predominant at the end of performance studies.     

Comparison of startup and anaerobic wastewater treatment in UASB, hybrid and baffled reactor

An experimental study was carried out to compare the performance of selected anaerobic high rate reactors operated simultaneously at 37?°C. The three reactors, namely upflow anaerobic sludge bed reactor (UASB), hybrid of UASB reactor and anaerobic filter (anaerobic hybrid reactor – AHR) and anaerobic baffled reactor (ABR), were inoculated with the anaerobic digested sludge from municipal wastewater treatment plant and tested with synthetic wastewater. This wastewater contained sodium acetate and glucose with balanced nutrients and trace elements (COD 6000?mg?·?l^?1). Organic loading rate (B _v ) was increased gradually from an initial 0.5?kg?·?m^?3?·?d^?1 to 15?kg?·?m^?3?·?d^?1 in all the reactors. From the comparison of the reactors' performance, the lowest biomass wash-out resulted from ABR. In the UASB, significant biomass wash-out was observed at the B _v 6?kg?·?m^?3?·?d^?1, and in the AHR at the B _v 12?kg?·?m^?3?·?d^?1. The demand of sodium bicarbonate for pH maintenance in ABR was two times higher as for UASB and AHR. The efficiency of COD removal was comparable for all three reactors – 80–90%. A faster biomass granulation was observed in the ABR than in the other two reactors. This fact is explained by the kinetic selection of filamentous bacteria of the Methanotrix sp. under a high (over 1.5?g?·?l^?1) acetate concentration.     

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.     

Experiments and ANFIS modelling for the biodegradation of penicillin-G wastewater using anaerobic hybrid reactor

The performance of an anaerobic hybrid reactor (AHR) for treating penicillin-G wastewater was investigated at the ambient temperatures of 30-35 °C for 245 days in three phases. The experimental data were analysed by adopting an adaptive network-based fuzzy inference system (ANFIS) model, which combines the merits of both fuzzy systems and neural network technology. The statistical quality of the ANFIS model was significant due to its high correlation coefficient R² between experimental and simulated COD values. The R² was found to be 0.9718, 0.9268 and 0.9796 for the I, II and III phases, respectively. Furthermore, one to one correlation among the simulated and observed values was also observed. The results showed the proposed ANFIS model was well performed in predicting the performance of AHR.     

Combined industrial and domestic wastewater treatment by periodic allocating water hybrid hydrolysis acidification reactor followed by SBR

A pilot-scale hybrid hydrolysis acidification reactor (HHAR) with periodic water allocation mode operation followed by sequencing batch reactor (SBR) in anoxic and aerobic metabolic function was evaluated for the treatment of low-biodegradable combined industrial and domestic wastewater. The HHAR combines the advantages of both the UASB reactor and AF, omitting the three-phase separator. Furthermore, it has lower average up-flow velocity (0.38–0.92 m/h) and higher periodic up-flow velocity (6 m/h), which made the reactor keep higher MLSS concentration (more than 10,000 mg/L) and sludge-bed is in periodic “expansion-sedimentation-expansion” state. When HRT less than 10 h, the B/C variation was positive and reached the maximum value of 0.07 at 8 h. SBR with a total cycle period of 4.5 h was applied as the post-treatment process to remove residual COD, NH₃-N and TN. At steady stage, the pilot-scale SBR effluent COD, NH₃-N and TN concentration was 65, 0.75 and 17.71 mg/L, corresponding in this case to full-scale SBR plant effluent was 93, 16.4 and 34 mg/L. Comparison results indicated that the application of HHAR–SBR system to treat combined industrial and domestic wastewater can improve effluent quality significantly.     

Treatment of slaughterhouse wastewater in a UASB reactor and an anaerobic filter

A study was performed to assess the feasibility of anaerobic treatment of slaughterhouse wastewaters in a UASB (Upflow Anaerobic Sludge Blanket) reactor and in an AF (Anaerobic Filter). Among the different streams generated, the slaughter line showed the highest organic content with an average COD of 8000 mg/l, of which 70% was proteins. The suspended solids content represented between 15 and 30% of the COD. Both reactors had a working volume of 21. They were operated at 37°C. The UASB reactor was run at OLR (Organic Loading Rates) of 1–6.5 kg COD/m³/day. The COD removal was 90% for OLR up to 5 kg COD/m³/day and 60% for an OLR of 6.5 kg COD/m³/day. For similar organic loading rates, the AF showed lower removal efficiencies and lower percentages of methanization. At higher OLR sludge, flotation occurred and consequently the active biomass was washed out from the filter. The results indicated that anaerobic treatment systems are applicable to slaughterhouse wastewaters and that the UASB reactor shows a better performance, giving higher COD removal efficiencies than the AF.     

Treatment of brewery wastewater using anaerobic sequencing batch reactor (ASBR)

Brewery wastewater was treated in a pilot-scale anaerobic sequencing batch reactor (ASBR) in which a floating cover(@) was employed. Long time experiments showed that the reactor worked stably and effectively for COD removal and gas production. When the organic loading rate was controlled between 1.5 kg COD/m3 d and 5.0 kg COD/m(3)d, and hydraulic retention time one day, COD removal efficiency could reach more than 90%. Sludge granulation was achieved in the reactor in approximately 60 days, which is much less than the granulation time ever reported. In addition, high specific methanogenic activity (SMA) for formate was observed. The study suggests that the ASBR technology is a potential alternative for brewery wastewater treatment.     

Kinetics of anaerobic purification of industrial wastewater

As a part of the development of an integral mathematical model describing the up-flow anaerobic sludge blanket (UASB) reactor, the kinetics of the conversion of organic wastes has to be known. We compared the Monod model with the model proposed by Andrews et al. Together with the assumption that the substrate for the anaerobic bacteria is formed by nonionized, volatile fatty acids, the Andrews model is able to describe substrate inhibition and reactor failure due to pH changes.From four batch experiments, with different concentrations of microorganisms, it could be concluded with a reliability of over 95% that the monod model was inadequate and Andrews' model was adequate to describe the measurements. Standard statistical techniques like the X2- and the F-test were used for this purpose.From a parameter sensitivity analysis for the Andrews model it followed that the maximum specific growth rate mu(A) (max) of the bacteria and the inhibition constant K(1) are the parameters which influence the system most. Thus, these parameter were determined experimentally and most accurately. The results are: \documentclass{article}\pagestyle{empty}\begin{document}$$\mu;{A}_{\max} = 16*10;{-4}{\rm h};{-1}\pm 2\%\quad {\rm and}\quad K_l = 0.0158\,{\rm g}\,{\rm HAc/L}\pm 2.5\%$$\end{document} The other parameters were taken from literature. From calculation of the Thiele modulus for the particles it follows that transport limitation of the substrate in the flocus is not significant. The efficiency eta is 0.85 in the worst case.     

Performance of inverse anaerobic fluidized bed reactor for treating high strength organic wastewater during start-up phase

The aim of this work is to report on the physical characteristics of carrier material (perlite), biomass growth on the carrier material and the biogas production during an apparent steady state period in an inverse anaerobic fluidized bed reactor (IAFBR) for treating high strength organic wastewater. Before starting up the reactor, physical properties of the carrier material were determined. One millimeter diameter perlite particle is found to have a wet specific density of 295 kg/m(3) with specific surface area of 7.010 m(2)/g. This material has provided a good surface for biomass attachment and development. The biofilm concentration (in terms of attached volatile solids (AVS)) attached to carrier material was found to be 0.66 g(AVS)/g(solid). Most particles have been covered with a thin biofilm of uniform thickness. Once the inverse anaerobic fluidized bed system reached the steady state, the organic load was increased step wise by reducing hydraulic retention time (HRT) from 2 days to 0.16 day, while maintaining the constant feed of chemical oxygen demand (COD) concentration. This system has achieved 84% COD removal and reached the biogas production of 13.22 l/l/d at an organic loading rate (OLR) of 35 kgCOD/m(3)/d.     

Anaerobic treatment of a chemical synthesis-based pharmaceutical wastewater in a hybrid upflow anaerobic sludge blanket reactor

In this study, performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor, treating a chemical synthesis-based pharmaceutical wastewater, was evaluated under different operating conditions. This study consisted of two experimental stages: first, acclimation to the pharmaceutical wastewater and second, determination of maximum loading capacity of the hybrid UASB reactor. Initially, the carbon source in the reactor feed came entirely from glucose, applied at an organic loading rate (OLR) 1 kg COD/m(3) d. The OLR was gradually step increased to 3 kg COD/m(3) d at which point the feed to the hybrid UASB reactor was progressively modified by introducing the pharmaceutical wastewater in blends with glucose, so that the wastewater contributed approximately 10%, 30%, 70%, and ultimately, 100% of the carbon (COD) to be treated. At the acclimation OLR of 3 kg COD/m(3) d the hydraulic retention time (HRT) was 2 days. During this period of feed modification, the COD removal efficiencies of the anaerobic reactor were 99%, 96%, 91% and 85%, and specific methanogenic activities (SMA) were measured as 240, 230, 205 and 231 ml CH(4)/g TVS d, respectively. Following the acclimation period, the hybrid UASB reactor was fed with 100% (w/v) pharmaceutical wastewater up to an OLR of 9 kg COD/m(3) d in order to determine the maximum loading capacity achievable before reactor failure. At this OLR, the COD removal efficiency was 28%, and the SMA was measured as 170 ml CH(4)/g TVS d. The hybrid UASB reactor was found to be far more effective at an OLR of 8 kg COD/m(3) d with a COD removal efficiency of 72%. At this point, SMA value was 200 ml CH(4)/g TVS d. It was concluded that the hybrid UASB reactor could be a suitable alternative for the treatment of chemical synthesis-based pharmaceutical wastewater.     

Treatment of distillery spentwash by hybrid UASB reactor

A laboratory-scale hybrid UASB reactor, which combined an UASB in the lower part and a filter in the upper part, was used for the treatment of distillery spentwash. The reactor was operated under ambient conditions for 380 days. Using anaerobically digested sewage sludge as a seed, the start-up of the reactor and the cultivation of active granular sludge was completed within three months period. Scanning electron microscopic (SEM) observation of the granules showed the presence of Mehtanonthrix-like bacteria as the dominant species. Following the start-up the organic loading rate (OLR) was increased, stepwise, to 36 kg COD/m³ · d at a constant hydraulic retention time (HRT) of 6 h. COD removal efficiency was 80% even at a high OLR of 36 kg COD/m³ · d. Biogas rich in methane content (80%), with a maximum specific biogas yield of 0.40 m³ CH₄/kg · COD was produced. Polypropylene pall rings filter medium in the upper-third of the reactor was very effective as a gas-liquid-solid (GLS) separator, and retained the biomass in addition. The study indicated that hybrid UASB is a very feasible alternative for the treatment of high-strength wastewaters like distillery spentwash.     

Kinetic modelling and performance prediction of a hybrid anaerobic baffled reactor treating synthetic wastewater at mesophilic temperature

A modelling study on the anaerobic digestion process of a synthetic medium-strength wastewater containing molasses as a carbon source was carried out at different influent conditions. The digestion was conducted in a laboratory-scale hybrid anaerobic baffled reactor with three compartments and a working volume of 54 L, which operated at mesophilic temperature (35 °C). Two different kinetic models (one model was based on completely stirred tank reactors (CSTR) in series and the other an axial diffusion or dispersion model typical of deviations of plug-flow reactors), were assessed and compared to simulate the organic matter removal or fractional conversion. The kinetic constant (k) obtained by using the CSTR in series model was 0.60 ± 0.07 h⁻¹, while the kinetic parameter achieved with the dispersion model was 0.67 ± 0.06 h⁻¹, the dispersion coefficient (D) being 46. The flow pattern observed in the reactor studied was intermediate between plug-flow and CSTR in series systems, although the plug-flow system was somewhat predominant. The dispersion model allowed for a better fit of the experimental results of fractional conversions with deviations lower than 8% between the experimental and theoretical values. By contrast, the CSTR in series model predicted the behaviour of the reactor somewhat less accurately showing deviations lower than 10% between the experimental and theoretical values of the fractional conversion.     

Research on soybean protein wastewater treatment by the integrated two-phase anaerobic reactor

The start-up tests of treating soybean protein wastewater by the integrated two-phase anaerobic reactor were studied. The results showed that the soybean protein wastewater could be successfully processed around 30 days when running under the situation of dosing seed sludge with the influent of approximately 2000 mg/L and an HRT of 40 h. When the start-up was finished, the removal rate of COD by the reactor was about 80%. In the zone I, biogas mainly revealed carbon dioxide (CO₂) and hydrogen (H₂). Methane was the main component in the zone 2 which ranged from 53% to 59% with an average of 55%. The methane content in biogas increased from the zone I to II. It indicated that the methane-producing capacity of the anaerobic sludge increased. It was found that the uniquely designed two-phase integrated anaerobic reactor played a key role in treating soybean protein wastewater. The acidogenic fermentation bacteria dominated in the zone I, while methanogen became dominant in the zone II. It realized the relatively effective separation of hydrolysis acidification and methanogenesis process in the reactor, which was benefit to promote a more reasonable space distribution of the microbial communities in the reactor. There were some differences between the activities of the sludge in the two reaction zones of the integrated two-phase anaerobic reactor. The activity of protease was higher in the reaction zone I. And the coenzyme F₄₂₀ in the reaction zone II was twice than that in the reaction zone I, which indicated that the activity of the methanogens was stronger in the reaction zone II.     

Aerobic granulation with low strength wastewater at low aeration rate in A/O/A SBR reactor

The formation of aerobic granules with low organic loading synthetic wastewater (150-200 mg L⁻¹ of influent COD, acetate/propionate = 1/3) at low aeration rate (0.6 cm s⁻¹ of superficial gas velocity) had been investigated in the anaerobic/oxic/anoxic SBR. Aerobic granules with smooth surface and compact structure were successfully obtained after 50 days. However, these aerobic granules were unstable when the d(0.9) of granules increased to more than 1 mm. The results suggested that the aerobic granules with small diameter (smaller than 1000 μm) were more favorable for treating the low substrate loading wastewater at the low aeration rate. The cycle test revealed that most of the influent COD was removed at the anaerobic stage. The effluent concentrations of N-NH₄⁺ and P-PO₄³⁻ were lower than 1 mg L⁻¹, and the effluent concentration of nitrate gradually decreased with the granulation. Phosphate accumulating organisms were found to utilize O₂ or NO_x⁻ as electron acceptor for phosphorus removal in the study. Simultaneous nitrogen and phosphorus removal occurred inside the granules.     

Performance of a hybrid anaerobic reactor,combining a sludge blanket and a filter,treating slaughterhouse wastewater

A column reactor, in which the bottom two-thirds were occupied by a sludge blanket and the upper one-third by submerged clay rings, was evaluated using slaughterhouse wastewater as substrate. The reactor was operated at 35°C at loading rates varying from 5 g to 45 g chemical oxygen demand (COD) 1^–1 × day^–1 at an influent concentration of 2450 mg COD 1^–1. A maximum substrate removal rate of 32 g COD 1^–1 × day^–1, coupled with a methane production rate of 6.91 × 1^–1 × day^–1 (STP), was obtained. This removal rate is significantly higher than those previously reported. The rate of substrate utilization by the biomass was 1.22 g COD (g volatile suspended solids)^–1 day^–1. COD removal was over 96% with loading rates up to 25 g COD 1^–1 × day^–1, at higher loading rates performance decreased rapidly. It was found that the filter element of the reactor was highly efficient in retaining biomass, leading to a biomass accumulation yield coefficient of 0.029 g volatile suspended solids g^–1 COD, higher than reported previously for either upflow anaerobic sludge-blanket reactors or anaerobic filters operating independently.