Bio-kinetic analysis on treatment of textile dye wastewater using anaerobic batch reactor

An anaerobic digestion technique was applied to textile dye wastewater aiming at the colour and COD removal. Pet bottles of 5 L capacity were used as reactor which contains methanogenic sludge of half a liter capacity which was used for the treatment of combined synthetic textile dye and starch wastewater at different mixing ratios of 20:80, 30:70, 40:60, 50:50 and 60:40 with initial COD concentrations as 3520, 3440, 3360, 3264 and 3144 mg L⁻¹, respectively. The reactor was maintained at room temperature (30 ± 3 °C) with initial pH of 7. The maximum COD and colour removal were 81.0% and 87.3% at an optimum mixing ratio of 30:70 of textile dye and starch wastewaters. Both Monod’s and Haldane’s models were adopted in this study. The kinetic constants of cell growth under Haldane’s model were satisfactory when compared to Monod’s model. The kinetic constants obtained by Haldane’s model were found to be in the range of μ_max = 0.037-0.146 h⁻¹, K_s = 651.04-1372.88 mg L⁻¹ and K_i = 5681.81-18727.59 mg L⁻¹.     

Aerobic treatment of dairy wastewater with sequencing batch reactor systems

Performances of single-stage and two-stage sequencing batch reactor (SBR) systems were investigated for treating dairy wastewater. A single-stage SBR system was tested with 10,000 mg/l chemical oxygen demand (COD) influent at three hydraulic retention times (HRTs) of 1, 2, and 3 days and 20,000 mg/l COD influent at four HRTs of 1, 2, 3, and 4 days. A 1-day HRT was found sufficient for treating 10,000-mg/l COD wastewater, with the removal efficiency of 80.2% COD, 63.4% total solids, 66.2% volatile solids, 75% total Kjeldahl nitrogen, and 38.3% total nitrogen from the liquid effluent. Two-day HRT was believed sufficient for treating 20,000-mg/l COD dairy wastewater if complete ammonia oxidation is not desired. However, 4-day HRT needs to be used for achieving complete ammonia oxidation. A two-stage system consisting of an SBR and a complete-mix biofilm reactor was capable of achieving complete ammonia oxidation and comparable carbon, solids, and nitrogen removal while using at least 1/3 less HRT as compared to the single SBR system.     

Biological treatment of low-salinity shrimp aquaculture wastewater using sequencing batch reactor

In order to improve the water quality in shrimp aquaculture operated under low-salinity conditions, a sequencing batch reactor (SBR) was tested for treatment of the wastewater. This water from the backwash of a single-bead filter from the Waddell Mariculture Center, South Carolina, contained high concentrations of carbon and nitrogen and was successfully treated using the SBR. By operating the reactor sequentially in aerobic, anoxic and aerobic modes, nitrification and denitrification were achieved, as well as removal of carbon. Specifically, the initial chemical oxygen demand (COD) concentration of 1201 mg l⁻¹ was reduced to 32 mg l⁻¹ within 8 days of reactor operation. Ammonia in the sludge was nitrified within 3 days. The denitrification of nitrate was achieved by the anoxic process and total removal of nitrate was observed.     

Bioaugmentation treatment for coking wastewater containing pyridine and quinoline in a sequencing batch reactor

Two pyridine-degrading bacteria and two quinoline-degrading bacteria were introduced for bioaugmentation to treat the coking wastewater. Sequencing batch reactors (SBRs) were used for a comparative study on the treatment efficiency of pyridine, quinoline, and chemical oxygen demand. Results showed that the treatment efficiency with coking-activated sludge plus a mixture of the four degrading bacteria was much better than that ones with coking-activated sludge only or mixed degrading bacteria only. Moreover, a 52-day continuous operation of the bioaugmented and general SBRs was investigated. The bioaugmented SBR showed better treatment efficiency and stronger capacity to treat high pyridine and quinoline shock loading. The general SBR failed to cope with the shock loading, and the biomass of the activated sludge decreased significantly. In order to monitor the microbial ecological variation during the long-term treatment, the bacterial community in both reactors was monitored by the amplicon length heterogeneity polymerase chain reaction technique. The diversity of the bacterial community decreased in both reactors, but the introduced highly efficient bacteria were dominant in the bioaugmented SBR. Our experiment showed clearly that the use of highly efficient bacteria in SBR process could be a feasible method to treat wastewater containing pyridine or/and quinoline.     

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.     

N-removal in a granular sludge sequencing batch airlift reactor

The removal of N-compounds in the sequencing batch airlift reactor (SBAR) containing granular sludge was studied under conditions of decreased dissolved oxygen (DO). A simulation model was developed to describe and evaluate the effects of several process conditions in the SBAR on N-removal performance. The model described the experimental data reasonable well. It has been shown that nitrification, denitrification, and removal of chemical oxygen demand (COD) can occur simultaneously in a granular sludge SBR. It has also been shown that the exact location of the autotrophic biomass influences the net N-removal. The distribution of the autotrophic biomass is influenced by the DO in the reactor. The optimal DO value is expected to be around 40% air saturation. It was shown that storage and subsequent degradation of poly-beta-hydroxybutyrate (PHB) benefit the denitrification. In particular, PHB is stored in bacteria situated in deeper layers of the granules below where the autotrophic activity occurs, serves as a C-source for denitrification.     

Small-scale domestic wastewater treatment using an alternating pumped sequencing batch biofilm reactor system

An alternating pumped sequencing batch biofilm reactor (APSBBR) system was developed to treat small-scale domestic wastewater. This laboratory system had two reactor tanks, Reactor 1 and Reactor 2, with two identical plastic biofilm modules in each reactor. Reactor 1 of the APSBBR had five operational phases—fill, anoxic, aerobic, settle and draw. In the aerobic phase, the wastewater was circulated between the two reactor tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by microorganisms in the biofilms when they were exposed to the air. This paper details the performance of the APSBBR system in treating synthetic domestic wastewater over 18 months. The effluent from the APSBBR system satisfied the European Wastewater Treatment Directive requirements, with respect to COD, ammonium-nitrogen and suspended solids. The biofilm growth in the two reactor tanks was different due to the difference in substrate loadings and growth conditions.     

Variable aeration in sequencing batch reactor with aerobic granular sludge

This study investigated the effects of reduced aeration in famine period on the performance of sequencing batch reactor (SBR) with aerobic granular sludge. Aerobic granules were first cultivated in two SBRs (R1 and R2) with acetate as sole carbon source. From operation day 27, aeration rate in R1 was reduced from 1.66 to 0.55 cm s(-1) from 110 min to the end of each cycle and further reduced from 30 min to the end of each cycle from day 63. R2 as a control was operated with a constant aeration rate of 1.66 cm s(-1) in the whole cycle during the entire experimental period. Results showed that changing trends of SVI, concentration, average size and VSS/SS of biomass with time in R1 and R2 were similar although different aeration modes were adopted. At steady state, SVI of aerobic granules and biomass concentration maintained at about 40 ml g(-1) and 6 g l(-1), respectively. Average size of granules was about 750 microm in R1 while 550 microm in R2. This is the first study to demonstrate that aerobic granular sludge could be stable at reduced aeration rate in famine period during more than 3-month operation. Such an operation strategy with reduced aeration rate will lead to a significant reduction of energy consumption, which makes the aerobic granular sludge technology more competitive over conventional activated sludge process. Furthermore, the stability of aerobic granular system with variable aeration further indicates that the difference of physiology and kinetics of aerobic granule in feast and famine periods results in the different requirements of oxygen and shear stress for the stability of granules, which will deepen the understanding of mechanism of aerobic granulation in sequencing batch reactor.     

Bioaugmentation with a novel alkali-tolerant Pseudomonas strain for alkaline phenol wastewater treatment in sequencing batch reactor

A novel alkali-tolerant strain JY-2, which could utilize phenol as sole source of carbon and energy, was isolated from activated sludge. It was identified as Pseudomonas sp. by 16S rDNA sequencing analysis. The appropriate conditions for strain growth and phenol biodegradation were as follows: pH 8.0–10.0 and temperature 23–30°C. With initial phenol concentrations of 225, 400, 550 and 750 mg/l, the degradation efficiencies were 94.9, 93.3, 89.3 and 48.2% within 40 h at pH 10.0 and 30°C, respectively. The alkaline phenol-containing wastewater treatment augmented with strain JY-2 in sequencing batch reactor (SBR) system was investigated, which suggested that the bioaugmented (BA) system exhibited the better performance for adjusting high pH to neutral value than the non-bioaugmented (non-BA) one. Also, the BA system showed strong abilities for phenol degradation and maintaining good sedimentation coefficient (SV₃₀). The microbial community dynamics of both sequencing batch reactor (SBR) systems were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE) technique, which showed substantial changes between the two systems. This study suggests that it is feasible to treat alkaline phenol-containing wastewater augmented with strain JY-2.     

Pretreatment of textile dyeing wastewater using an anoxic baffled reactor

A study on pretreatment of textile dyeing wastewater was carried out using an anoxic baffled reactor (ABR) at wastewater temperatures of 5-31.1 degrees C. When hydraulic retention time (HRT) was 8h, the color of outflow of ABR was only 40 times at 5 degrees C and it could satisfy the professional discharge standard (grade-1) of textile and dyeing industry of China (GB4287-92). The total COD removal efficiency of ABR was 34.6%, 47.5%, 50.0%, 53.3%, 54.7% and 58.1% at 5, 9.7, 14.9, 19.7, 23.5 and 31.1 degrees C, respectively. Besides, after the wastewater being pre-treated by ABR when HRT was 6h and 8h, the BOD5/COD value rose from 0.30 of inflow to 0.46 of outflow and from 0.30 of inflow to 0.40 of outflow, respectively. Experimental results indicated that ABR was a very feasible process to decolorize and pre-treat the textile dyeing wastewater at ambient temperature. Moreover, a kinetic simulation of organic matter degradation in ABR at six different wastewater temperatures was carried through. The kinetic analysis showed the organic matter degradation was a first-order reaction. The reaction activation energy was 19.593 kJ mol(-1) and the temperature coefficient at 5-31.1 degrees C was 1.028.     

Aerobic granulation with brewery wastewater in a sequencing batch reactor

Aerobic granular sludge was cultivated in a sequencing batch reactor fed with brewery wastewater. After nine-week operation, stable granules with sizes of 2-7 mm were obtained. With the granulation, the SVI value decreased from 87.5 to 32 mL/g. The granular sludge had an excellent settling ability with the settling velocity over 91 m/h. Aerobic granular sludge exhibited good performance in the organics and nitrogen removal from brewery wastewater. After granulation, high and stable removal efficiencies of 88.7% COD(t), 88.9% NH(4)(+)-N were achieved at the volumetric exchange ratio of 50% and cycle duration of 6h. The average COD(t) and COD(s) of the effluent were 212 and 134 mg/L, respectively, and the average effluent ammonium concentration was less than 14.4 mg/L. Nitrogen was removed due to nitrification and simultaneous denitrification in the inner core of granules.     

Kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket reactor

The kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket (UASB) reactors was investigated. Different concentrations of organic matter in slaughterhouse wastewater did not change the first order kinetics of the reaction. In batch digesters, methane and nitrogen production stopped after 30-40, 20-30 h, respectively, and in UASB reactors it was terminated after 30-40 days. The constant of velocity was 3.93 and 0.23 h(-1) respectively, for methane and nitrogen production. The yield coefficient, Yp was 343 and 349 ml CH4 per g of chemical oxygen demand at standard temperature and pressure conditions for batch reactors and UASB reactor, respectively.     

Electrochemical oxidation for the treatment of textile industry wastewater

This study elucidates the reduction of organics from textile effluents through electrochemical oxidation technique. Effect of pH and current intensity were investigated in this system. It was found that degradation was maximum at the current intensity of 0.6 A and at a pH of 1.3. Under the same experimental conditions the removal of chemical oxygen demand (COD), total solids, total dissolved solids and total organic carbon were found to be approximately 68%, 49.2%, 50.7% and 96.8%, respectively. Effect of current intensity on color removal was also investigated as a function of electrolysis time (30-210 minutes) and it showed that maximum removal efficiency (96%) was reached within 60 minutes at 0.6 A. While studying the effect of pH on COD removal, it was observed that a decrease in pH to an optimum of 1.3 showed maximum COD reduction of 68%. These results suggest an important role of these parameters in electrochemical process for removing organic pollutants.     

Degradation of synthetic reactive azo dyes and treatment of textile wastewater by a fungi consortium reactor

In this paper, two microbial cultures with high decolorization efficiencies of reactive dyes were obtained and were proved to be dominant with fungi consortium in which 21 fungal strains were isolated and 8 of them showed significant decolorization effect to reactive red M-3BE. A 4.5 l continuous biofilm reactor was established using the mixed cultures to investigate the decolorization performance and the system stability under the conditions of simulated and real textile wastewater as influents. The optimal nutrient feed to this bioreactor was 0.5 g l⁻¹ glucose and 0.1 g l⁻¹ (NH₄)₂SO₄ when 30 mg l⁻¹ reactive black 5 was used as initial dye concentrations. Dye mineralization rates of 50–75% and color removal efficiencies of 70–80% were obtained at 12 h hydraulic retention time (HRT) in this case. Higher glucose concentrations in the influents could significantly improve color removal, but was not helpful for dye mineralization. Besides reactive black 5, the bioreactor could effectively decolorize reactive red M-3BE, acid red 249 and real textile wastewater with efficiency of 65%, 94% and 89%, respectively. In addition, the microbial community on the biofilm was monitored in the whole running process. The results indicated fungi as a dominant population in the decolorization system with the ratio of fungi to bacteria 6.8:1 to 51.8:1 under all the tested influent conditions. Analysis of molecular biological detection indicated that yeasts of genus Candida occupied 70% in the fungal clone library based on 26S rRNA gene sequences.     

Enhanced biological phosphate removal by granular sludge in a sequencing batch reactor

A laboratory-scale sequencing batch reactor was started-up with flocculated biomass and operated primarily for enhanced biological phosphate removal. Ten weeks after the start-up, gradual formation of granular sludge was observed. The compact biomass structure allowed halving the settling time, the initial reactor volume, and doubling the influent COD concentration. Continued operation confirmed the possibility of maintaining a stable granular biomass with a sludge volume index less than 40 ml g^–1, while securing a removal efficiency of 95% for carbon, 99.6% for phosphate, and 71% for nitrogen. Microscopic observations revealed a morphological diversity.     

Evaluation of an on-site pilot static granular bed reactor (SGBR) for the treatment of slaughterhouse wastewater

An on-site pilot-scale static granular bed reactor (SGBR) system was evaluated for treating wastewater from a slaughterhouse in Iowa. The study evaluated SGBR reactor suitability for slaughterhose wastewater having high particulate COD concentration (7.9 ± 4.3 g COD/L) at 0.3–1.4 m³/m²/day of the surface loading rates. High organic removal efficiency (over 95% of TSS and VSS removal) was obtained due to the consistent treatability of SGBR system during operation at HRTs of 48, 36, 30, 24, and 20 h. The average effluent TSS, VSS, COD, soluble COD, and BOD₅ concentrations were 84, 71, 301,197, and 87 mg/L, respectively. An effective backwash procedure was performed once every 7–14 days to waste a portion of the accumulated solids in the system. This procedure limited the increase in hydraulic head loss and maintained the system stability. COD removal efficiencies greater than 95% were achieved at organic loading rates ranging from 0.77 to 12.76 kg/m³/day.     

Treatment of dairy effluents in an aerobic granular sludge sequencing batch reactor

Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15–30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% COD_total, 80% N_total and 67% P_total can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l^–1 COD_dissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.     

Simulation of wastewater treatment by aerobic granules in a sequencing batch reactor based on cellular automata

In the present paper, aerobic granules were developed in a sequencing batch reactor (SBR) using synthetic wastewater, and 81 % of granular rate was obtained after 15-day cultivation. Aerobic granules have a 96 % BOD removal to the wastewater, and the reactor harbors a mount of biomass including bacteria, fungi and protozoa. In view of the complexity of kinetic behaviors of sludge and biological mechanisms of the granular SBR, a cellular automata model was established to simulate the process of wastewater treatment. The results indicate that the model not only visualized the complex adsorption and degradation process of aerobic granules, but also well described the BOD removal of wastewater and microbial growth in the reactor. Thus, CA model is suitable for simulation of synthetic wastewater treatment. This is the first report about dynamical and visual simulation of treatment process of synthetic wastewater in a granular SBR.     

Carbon membrane-aerated biofilm reactor for synthetic wastewater treatment

A carbon membrane-aerated biofilm reactor (CMABR) was developed to treat synthetic wastewater. Such membrane exhibited a high degree of adhesion and good permeability. Continuous experiments showed that COD and -N removal efficiency were 90 ± 2 and 92 ± 4% at removal rates of 35.6 ± 3.8 g COD/m² per day and 9.3 ± 0.6 g -N/m² per day, respectively. After 108 days, effluent total nitrogen (TN) kept at 35 ± 4 mg/L when influent -N increased to 144–164 mg/L and removal efficiency of TN reached 78 ± 3%. Furthermore, Stoichiometric analysis revealed that 70–90% of oxygen supplied was consumed by nitrifier. Scanning electron microscopic (SEM) images and component analysis of penetrating fluid revealed that extracellular polymeric substance (EPS) adhered to pore and that alkaline washing was an effective method to remove them. The study demonstrated that carbon membrane could be used as effective gas-permeable membrane in MABR for wastewater treatment.