Continuous fill intermittent decant type sequencing batch reactor application to upgrade the UASB treated sewage

The performance of continuous flow intermittent decant type sequencing batch (CFID) reactor treating the effluent of an UASB reactor treating domestic wastewater and operated at 8 h hydraulic retention time (HRT) was investigated. The CFID was operated at three different HRTs (22, 8 and 6 h) and three different dissolved oxygen (DO) patterns (<0.5, 2.5–3.5 and 3.5–4.5 mg/L). The highest effluent quality was observed at the 8 h HRT and 2.5–3.5 mg/L DO concentration. At this operational condition, the average BOD, TSS, ammonia nitrogen and fecal coliform removal efficiencies were 83, 90, 74 and 99 %, respectively. The CFID is a promising post-treatment option for existing UASB systems, with a final effluent quality that comply with receiving water and effluent reuse criteria.     

Treatment of tomato processing wastewater by an upflow anaerobic sludge blanket-anoxic-aerobic system

The main objective of this study is to assess the achievability of stringent discharge criteria i.e. BOD(5)<15 mg/L, TSS<15 mg/L and NH(4)-N<1mg/L during the treatment of tomato processing wastewater with COD of 2800-15,500 mg/L, BOD(5) of 1750-7950 mg/L, TKN of 48-340 mg/L and NH(4)-N of 21-235 mg/L. Two treatment systems, a UASB-aerobic system and a UASB-anoxic-aerobic system were tested. Furthermore due to alkalinity deficiency, in the raw wastewater, the study explored varying UASB effluent recirculation flowrates to the UASB influent to reduce additional alkalinity requirements. The UASB-anoxic-aerobic system was effective in treating tomato canning wastewater at an overall HRT of 1.75 days while achieving 98.5% BOD(5), 95.6% COD, 84% TSS and 99.5% NH(4)-N removal producing effluent BOD(5), COD, TSS, NH(4)-N, TKN, NO(2)-N, NO(3)-N and PO(4)-P of 10, 70, 15, 0.5, 3, 0, 60 and 4 mg/L, respectively. The biogas yield was 0.43 m(3)/kg COD removed.     

Nutrient recovery from domestic wastewater using a UASB-duckweed ponds system

The pilot-scale wastewater treatment system used in this study comprised a 40-l UASB reactor (6-h HRT) followed by three duckweed ponds in series (total HRT 15 days). During the warm season, the treatment system achieved removal values of 93%, 96% and 91% for COD, BOD and TSS, respectively. Residual values of ammonia, TKN and total phosphorus were 0.41 mg N/l, 4.4 mg N/l and 1.11 mg P/l, with removal efficiencies of 98%, 85% and 78%, respectively. The system achieved 99.998% faecal coliform removal during the warm season with final effluent containing 4 x 10(3) cfu/100 ml. During the winter, the system was efficient in removing COD, BOD and TSS but not nutrients. The system was deficient in the removal of faecal coliforms during the winter, producing effluent with 4.7 x 10(5) cfu/100 ml. During the warm season, the N removal consisted of 80% by plant uptake, 5% by sedimentation and 15% unaccounted for. A duckweed production rate of 33 t dry matter per hectare per 8 months was achieved.     

Organics, sulfates and ammonia removal from acrylic fiber manufacturing wastewater using a combined Fenton-UASB (2 phase)-SBR system

A combined Fenton-UASB (2 phase)-SBR system was employed to treat acrylic fiber manufacturing wastewater. The Chemical Oxygen Demand (COD) removal and effluent Biochemical Oxygen Demand (BOD) to COD were 65.5% and 0.529%, respectively, with the optimal Fenton conditions: ferrous was 300 mg/L; hydrogen peroxide was 500 mg/L; pH was 3.0; reaction time was 2.0 h. In two-phase UASB reactor, mesophilic operation (35±0.5 °C) was performed with hydraulic retention time (HRT) varied between 28 and 40 h. The results showed that with the HRT not less than 38 h, COD and sulfate removal were 65% and 75%, respectively. The greatest sizes of granule formed in the sulfate-reducing and methane-producing phases were 5 and 2 mm, respectively. Sulfate-reducing bacteria (SRB) accounted for 35% in the sulfate-reducing phase while methane-producing archaea (MPA) accounted for 72% in the methane-producing phase. During the SBR process, shortcut nitrification was achieved by temperature control of 30 °C.     

Treatment of wastewater from abattoirs before land application--a review

Pre-treatments are screening, catch basins, flotation, equalization, and settlers for recovering proteins and fats from abattoir wastewater. With chemical addition, dissolved air flotation (DAF) units can achieve chemical oxygen demand (COD) reductions ranging from 32% to 90% and are capable of removing large amounts of nutrients. Aerobic trickling towers reduced soluble COD by additional 27% but did not reduced total COD. Chemical-DAF reduced 67% of total COD and soluble COD. About 40-60% of the solids or approximately 25-35% of the biological oxygen demand (BOD) load can be separated by pre-treatment screening and sedimentation. Anaerobic systems are lagoon, anaerobic contact (AC), up-flow anaerobic sludge blanket (UASB), anaerobic sequence batch reactor (ASBR), and anaerobic filter (AF) processes. Abattoir wastewater is well suited to anaerobic treatment because it is high in organic compounds. Typical reductions of up to 97% BOD, 95% SS and 96% COD are reported. UASB's average COD removal efficiencies are of 80-85%. UASB seems to be a suitable process for the treatment of abattoir wastewater, due to its ability to maintain a sufficient amount of viable sludge. Wastewater in abattoirs can be reduced by treatment of immersion chiller effluent by membrane filtration which can produce recyclable water. Total organic C can be reduced below 100mg/L, and bacteria can not pass through the membrane pores. The abattoir waste minimization options are also discussed.     

Slaughterhouse wastewater treatment: evaluation of a new three-phase separation system in a UASB reactor.

The anaerobic treatment of the wastewater from the meat processing industry was studied using a 7.2 1 UASB reactor. The reactor was equipped with an unconventional configuration of the three-phase separation system. The effluent was characterized in terms of pH (6.3-6.6), chemical oxygen demand (COD) (2,000-6,000 mg l(-1)), biochemical oxygen demand BOD5 (1,300-2,300 mg 1(-1)), fats (40-600 mg l(-1)) and total suspended solids (TSS) (850-6,300 mg l(-1)) The reactor operated continuously throughout 80 days with hydraulic retention time of 14, 18 and 22 h. The wastewater from Rezende Industrial was collected after it had gone through pretreatment (screening, flotation and equalization). COD, BOD and TSS reductions and the biogas production rate were the parameters considered in analyzing the efficiency of the process. The average production of biogas was 111 day(-1) (STP) for the three experimental runs. COD removal varied from 77% to 91% while BOD removal was 95%. The removal of total suspended solids varied from 81% to 86%. This fact supports optimal efficiency of the proposed three-phase separation system as well as the possibility of applying it to the treatment of industrial effluents.     

Degradation of 4-chlorophenol in UASB reactor under methanogenic conditions

Treatment of simulated wastewater containing 40 mg/l of 4-chlorophenol (4-CP) was carried out in an upflow anaerobic sludge blanket (UASB) reactor under methanogenic condition. The performance of this test UASB reactor was evaluated in terms of 4-CP removal. Hydraulic retention time (HRT) and substrate:co-substrate ratio for the 4-CP removal was optimized by varying the influent flow rate (13-34.7 ml/min) and sodium acetate concentration (2-5 g/l), respectively. A control UASB reactor, which was not exposed to 4-CP was also operated under similar conditions. Organic loading rate (OLR) was varied in the range of 2-5.3 kg/m(3)/d and 1.7-4.2 kg/m(3)/d, respectively, for HRT and substrate:co-substrate ratio studies, respectively. The optimum HRT and substrate:co-substrate ratio for the removal of 4-CP was 12h and 1:75, respectively. Removal of 4-CP achieved at optimum HRT and substrate:co-substrate ratio was 88.3+/-0.7%. Removal of 4-CP occurred through dehalogenation and caused increase in chloride ion concentration in the effluent by 0.23-0.27 mg/mg 4-CP removed. The ring cleavage test showed the ortho mode of ring cleavage of 4-CP. Change in the elemental composition of the anaerobic biomass of UASB reactors was observed during the study period. Concentration of Ca(2+) increased in the biomass and this could be attributed to the biosoftening. Specific methanogenic activity of the sludge of control and test UASB reactor was 0.832 g CH(4) COD/g VSS d and 0.694 g CH(4) COD/g VSS d, respectively.     

Pilot-scale experiment of down-flow hanging sponge for direct treatment of low-strength municipal wastewater in Bangkok,Thailand

A pilot-scale experiment of a down-flow hanging sponge (DHS) reactor for treatment of low-strength municipal wastewater was conducted over 1 year in Bangkok, Thailand, to establish an appropriate method for treatment under tropical climate conditions. Municipal wastewater with an average BOD of 19 mg/L was fed directly into the DHS reactor. Superior effluent quality (5.1 ± 3.4 mg/L TSS, 21.1 ± 9.0 mg/L COD, 2.8 ± 1.4 mg/L BOD, and 4.1 ± 1.0 mg/L TN) was achieved at a hydraulic retention time (HRT) of 1 h under an average temperature of 30 °C. The DHS reactor reached an actual HRT of 19.0 min, indicating good contact efficiency between wastewater and retained sludge. The DHS reactor retained dense sludge at 15.3–26.4 g VSS/L based on the sponge media volume. The sludge activity in terms of specific oxygen uptake rate was good. Excess sludge was produced as 0.051 g TSS/g COD removed (0.11 g TSS/g BOD removed), and a good SVI of 28 mL/g was observed. The sufficient performance was attributed to dense sludge with high activity, regardless of the low-strength wastewater. Overall, the DHS was advantageous owing to its simple operation, lack of operational problems, and low power consumption.     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

Anaerobic submerged membrane bioreactor (AnSMBR) for municipal wastewater treatment under mesophilic and psychrophilic temperature conditions

A pilot scale anaerobic submerged membrane bioreactor (AnSMBR) with an external filtration unit for municipal wastewater treatment was operated for 100 days. Besides gas sparging, additional shear was created by circulating sludge to control membrane fouling. During the first 69 days, the reactor was operated under mesophilic temperature conditions. Afterwards, the temperature was gradually reduced to 20 °C. A slow and linear increase in the filtration resistance was observed under critical flux conditions (7 L/(m2 h)) at 35 °C. However, an increase in the fouling rate probably linked to an accumulation of solids, a higher viscosity and soluble COD concentrations in the reactor was observed at 20 °C. The COD removal efficiency was close to 90% under both temperature ranges. Effluent COD and BOD5 concentrations were lower than 80 and 25 mg/L, respectively. Pathogen indicator microorganisms (fecal coliforms bacteria) were reduced by log(10)5. Hence, the effluent could be used for irrigation purposes in agriculture.     

Anaerobic treatment of the municipal wastewater under psychrophilic conditions

The article discusses possibilities of municipal wastewater treatment in various types of anaerobic reactors (UASB, UAF, AnSBR). The temperature during corresponding laboratory experiments varied between 9–23?°C. Real wastewater from WWTP Bratislava-Petr?alka and synthetic substrate were used in the experiments. The HRT values for reactors were found to be 10–46?h. Treatment of municipal wastewater with the AnSBR and UAF system has shown more positive results in laboratory scale studies then the UASB system. The mean removal efficiency of COD depended on the type of anaerobic reactor, temperature, used HRT and was found between 37–48% (UASB), 56–88% (AnSBR) and 46–90% (UAF).     

Potential treatment alternative for laboratory effluents

The Chemical Analysis Laboratory under study weekly generates 46.5 L effluent with low pH (0.7), high COD concentration (6535 mg O2/L), sulphate (10390 mg/L) and heavy metals (213 mg Hg/L, 55 mg Cr/L, 28 mg Al/L, 22 mg Fe/L, 10mg Cu/L, 4 mg Ag/L). A treatment sequence has been proposed using a physical chemical step (coagulation/flocculation or chemical precipitation) followed by a biological step (anaerobic treatment). Removals of COD (18%), turbidity (76%) and heavy metals (64-99%) were attained only after adjusting pH to 6.5, without requiring the addition of Al2(SO4)3 and FeCl3. Due to the low COD:sulphate ratio (0.9-1.3), it was possible to efficiently operate the UASB reactor (at the biological step) only upon mixing the effluent with household wastewater. COD, sulphate and heavy metals removals of 60%, 23% and 78% to 100%, respectively, were attained for 30% effluent in the reactor feed. The results pointed to the need of a pretreatment step and mixing the effluent in household wastewater prior to the biological step. This alternative is feasible as this can be achieved using sanitary wastewater generated in the university campus.     

人工湿地对猪场废水有机物处理效果的研究

分别以香根草 (Vetiveriazizanioides)和风车草 (Cyperusalternifolius)为植被 ,按 1.0m× 0 .5m×0 .8m建立人工湿地 ,通过 4季测试 ,研究其对猪场废水有机物的净化功能及其随季节、进水浓度及水力停留时间变化的规律 .结果表明 ,4个季节香根草或风车草人工湿地对COD和BOD有较稳定的去除效果 ,两湿地抗有机负荷冲击能力强 .在春季 ,停留时间 1～ 2d ,COD和BOD去除率分别为 70 %和 80 %;在夏季 ,进水COD高达 10 0 0～ 140 0mg·L-1情况下 ,COD去除率接近 90 %;在秋季 ,停留时间 1～ 2d ,COD和BOD去除率分别为 5 0 %～ 6 0 %和 5 0 %;在冬季 ,进水COD达 10 0 3mg·L-1情况下 ,COD去除率在 70 %以上 .COD、BOD和SS的去除率在两湿地间没有显著差异 .人工湿地污染物 (Y)随水力停留时间 (t)延长的降解遵从指数方程规律Yt=Y0 ·e( -kt) .在相同停留时间时 ,随进水污染物浓度 (x)提高的出水污染物浓度 (y)的回归关系遵从直线方程规律 y =a+bx .     

Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter

In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O₃-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O₃-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7 h, 9.2 h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O₃-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O₃-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O₃-BAF combine process for textile wastewater treatment.     

Some studies on UASB bioreactors for the stabilization of low strength industrial effluents

The suitability of two stage biomethanation process using upflow anaerobic sludge blanket (UASB) bioreactors was studied for the treatment of low strength industrial effluents like rice mill wastewater. Maximum VFA yield was 0.75 mg (as acetic acid) per mg of COD consumed at a flow rate of 25 ml/min. Hydraulic retention time (HRT) of 1 hr was found suitable for acidification process. In the methanogenic reactor, the overall BOD and COD reductions were 89% and 78% respectively at loading rate of 3 kg COD m^х d^у, and HRT of 30 hrs. Gas yield in methanogenic reactor was 0.56 lits. per kg COD consumed which contains 62% v/v methane.     

Operational factors and nutrient effects on activated sludge treatment of Pinus radiata kraft mill wastewater

The biodegradability of Pinus radiata bleached kraft mill wastewater by an activated sludge treatment during a period of 280 days was evaluated. The effect of varying hydraulic retention time (HRT) in the range of 48 to 4.5 h and nitrogen (N) and phosphorus (P) addition on removal of biological oxygen demand (BOD5), chemical oxygen demand (COD), suspended solids (TSS and VSS), total phenolic compounds, tannin and lignin and reduction of toxicity was investigated. Removal of BOD5 was higher than 90% when HRT varied from 16 to 6 h, but decreased when HRT was less than 6 h. Similar performance was observed for COD removal, which was about 60% when HRT was varied from 16 to 6 h. Removal of total phenolic compounds and tannin and lignin was seriously affected by HRT. N and P addition to maintaining a ratio of 100:5:0.3 provided optimal BOD5, COD and suspended solids removal when HRT varied from 16 to 7 h, and no toxicity (using Daphnia) was detected in the treated effluent. When HRT was less than 6 h, the system showed destabilisation and pH, COD, BOD5 and suspended solids removal decreased.     

Treatment of coke wastewater in a sequential batch reactor (SBR) at pilot plant scale

Coke wastewater is a highly toxic industrial effluent which is usually treated by a combination of physico-chemical and biological treatments. With the aim of completing prior studies carried out in CSTR, in this work we studied the treatment of coke wastewater in a pilot plant equipped with a 400 L stripping tank, a 350 L neutralization/homogenization tank and a 6 m high 1500 L sequential batch reactor (SBR), controlled by a PLC. Ammonia stripping efficiencies of 96% were obtained for HRT of 66 h. The biological treatment in the SBR led to removal efficiencies of 85% COD, 98% thiocyanate and 99% phenols for HRT of 115 h. Final concentrations in the effluent of 1.8 mg phenols/L, 5.4 mg SCN/L, 206 mg COD/L and 78 mg N-NH(4)(+)/L were obtained.     

Treatment of strong domestic sewage in a 96 m3 UASB reactor operated at ambient temperatures: two-stage versus single-stage reactor

A 96 m3 UASB reactor was operated for 2.5 years under different conditions to assess the feasibility of treating strong sewage (COD(tot) = 1531 mg/l) at ambient temperatures with averages of 18 and 25 degrees C for winter and summer respectively. During the first year, the reactor was operated as a two-stage system at OLRs in the range of 3.6-5.0 kg COD/m3 d for the first stage and 2.9-4.6 kg COD/m3 d for the second stage. The results of the first stage showed average removals of 51% and 60% for COD(tot) and COD(ss) respectively without significant effect of temperature. The second stage reactor was unstable. The temperature affected sludge stabilization. During the second year, the first stage was operated as a single-stage UASB reactor at half of the previous loading rates. The results showed an average removal efficiency of 62% for COD(tot) during summer, while it dropped to 51% during wintertime. However, the effluent suspended solids were stabilized with VSS/TSS ratio around 0.50 all over the year. The sludge in the single-stage reactor was well-stabilized and exerted an excellent settlability. During the last three months of research, sludge was discharged regularly from the single-stage UASB reactor. The results showed no significant improvement in the performance in terms of COD(tot). Based on the results of the experiment, a single-stage UASB reactor operated at relatively long HRT is preferred above two-stage system at the Jordanian conditions.     

Assessment of a UASB reactor with high ammonia concentrations: Effect of zeolite addition on process performance

The UASB process for wastewater treatment has been extensively studied, but the use of zeolite to improve UASB reactor performance has rarely been explored. In this study, a UASB reactor modified with natural zeolite operating at high nitrogen concentrations (0.5, 0.7 and 1 g/L) was evaluated. Two laboratory bioreactors, one with zeolite and one without, were operated at ambient temperatures ranging between 18 °C and 21 °C. The experimental phase had a start-up period of 21 days. In the reactor with zeolite, the pH was found to be between 7.9 and 9.1, with a COD removal efficiency of about 60% after 80 days of operation at ammonia concentrations of between 0.229 and 0.429 g/L in the effluent. In the reactor without zeolite, the pH was between 8.3 and 9.3, and the COD removal efficiency was about 40% at ammonia concentrations between 0.244 and 0.535 g/L in the effluent. The addition of zeolite also decreased the volatile suspended solids (VSS) concentration in the effluent, generating a biomass with larger granules and higher settling rates as compared to a UASB reactor without zeolite. Taking the lower ammonia concentration, the higher COD removal and the improved granulation into account, it can be concluded that natural zeolite positively influenced the behavior and performance of the UASB reactor operating with high nitrogen concentrations.     

Evaluation of a upflow anaerobic sludge blanket reactor with partial recirculation of effluent used to treat wastewaters from pulp and paper plants

The main purpose of this study was to evaluate the performance of a UASB reactor treating diluted black liquor from a Kraft pulp mill, which simulates an unbleached Kraft plant wastewater, under different operational conditions, including partial recycling of the effluent. The reactor's performance was evaluated from the standpoint of COD, pH, volatile acid concentration, alkalinity, concentration of methane in the biogas, and microbiological examinations of the sludge. Without recirculation the reduction of the HRT from 36 to 30h did not significantly affect the average COD removal efficiency. The parameter displaying the greatest variation was the average concentration of effluent volatile acids, which increased by 16%. With recirculation the reduction of the HRT from 30 to 24h increased the average COD removal efficiency from 75% to 78%. In this case, the average effluent alkalinity also showed an increase. The use of partial recirculation of the effluent did not improve significantly the COD removal under the operational conditions tested in this work, but it was possible to operate the reactor with lower hydraulic retention time without disintegration of the granules.