Wastewater fermentation and nutrient removal in sequencing batch reactors (original) (raw)
Related papers
Resources, Conservation and Recycling, 1994
The Sequencing Batch Reactor (SBR) system employing activated sludge process is an alternative wastewater treatment technology. A cycle of the conventional SBR system generally consists of five periods, with complete aeration during the React period to oxidize the organic matter and nitrify the ammonium-nitrogen of wastewater. Laboratory-scale reactors were used to evaluate the feasibility of incorporating alternative aerobic-anoxic-aerobic stages within the React period for simultaneous removal of organic matter, N and P. Two cycles of SBR process per day were maintained. Under the operation strategy of 0.75-h FILL, 8-h REACT (with continuous aeration), 3.25-h SETTLE, DRAW and IDLE periods, the treatment performance became consistent after running the system for two to four cycles (1-2 days). The percentages of both BOD5 and COD removal were around 94% from Cycle 2 onwards, the BOD5 content dropped from initial 251 mg L-1 to less than 14 mg L-1 in the final effluent. A steady nitrification (about 97%) was obtained from Cycle 4 onwards, with l mg NH+-N L-J and 25 mg NO~-N L-t present in the final effluent. This suggested that the time required for SBR system to acclimate and reach an equilibrium state was relatively short when compared with the time needed for continuous flow activated sludge system. The findings also show that 4-h aeration during the REACT period was long enough to achieve more than 90% nitrification. With the incorporation of a 3-h anoxic stage after the initial 4-h aeration of the REACT period, a satisfactory denitrification process was observed, with nitrate level dropped from 27 to around 8 mg L-~ within 3 h. The second aeration stage did not cause significant change in wastewater nitrogen content. The wastewater phosphate content declined rapidly during the initial 4-h aeration and P-release was not observed during the anoxic stage. A slight reduction of P was found in the second aeration stage suggesting that more P-uptake occurred in this stage. A 12-h cyclic SBR system with the incorporation of 4-h aerobic, 3-h anoxic and final 1-h aerobic stages into the 8-h REACT period was demonstrated to be able to remove C, N and P simultaneously.
The studies were carried out with simulated domestic wastewater (300±10 and 500 mg COD/L) and real domestic wastewater (290±10 mg COD/L). During these studies different organic loading rates (0.29, 0.82 and 1.1 kg COD/m 3 d for Set I and Set II, and 0.29 and 0.62 kg COD/m 3 d for Set III), hydraulic retention times (11, 15, 25 h), temperatures (10, 15, 25°C) and at different anaerobic sludge concentrations (about 5, 10 g VSS/L) in the reactor were applied and the performance of the reactor was tested. It was observed that treatment of low strength wastewaters under low temperature was possible. Even at the lowest temperature applied and lowest sludge amount the total organic matter (COD) removal was 65.2%. However, the COD removal and methane production decreased with decreasing temperature and HRT. The COD removal efficiencies decreased when the system was fed with settled real domestic wastewater probably due to more complex structure of the domestic wastewater and the presence of suspended solids even in small concentrations. These results showed that the ASBR process can be used for treatment of low strength wastewaters at low temperatures.
Sequencing Batch Reactor System for Nutrient Removal: ORP and pH Profiles
Journal of Chemical Technology & Biotechnology, 1996
The sequencing batch reactor (SBR) process is known for its flexibility to meet a wide range of treatment needs, including nutrient removal. However, information related to the operational stability of SBR nutrient removal systems and control parameters to adjust the cyclic duration is sparse. Consequently, this study was undertaken to identify process parameters (pH and oxidation reduction potential) that could be useful for monitoring and real-time control purposes. In general, the system achieved removal efficiencies of 91, 98 and 98%, respectively, for Chemical Oxygen Demand, total nitrogen and phosphate at the solids retention time of 10 days, with a cyclic duration of 6 h. Shock loadings of nitrogen (20 mg dm-3 of NHa-N, four cycles) exhibited little impact on effluent quality, except for a higher nitrate content. Activated sludge settled well throughout the entire study period. Several significant points associated with different reactions within SBR cycle, e.g. end of nitrification, end of phosphate release and completion of phosphate uptake, were identified in pH profiles. Slope changes in pH profiles (dpH/dt, or d2pH/dt2) were found to better represent the corresponding biological reactions. The application of these significant points in pH profiles as real time control parameters appears promising.
Water Research, 2005
The physical and biochemical characteristics of the biomass in three lab-scale sequencing batch reactors (SBR) treating a synthetic wastewater at a 20-day target solids retention time (SRT) were investigated. The synthetic wastewater feed contained biogenic compounds and 22 organic priming compounds, chosen to represent a wide variety of chemical structures with different N, P and S functional groups. At a two-day hydraulic retention time (HRT), the oxidation-reduction potential (ORP) cycled between À100 (anoxic) and 100 mV (aerobic) in the anoxic/aerobic SBR, while it remained in a range of 126718 and 249718 mV in the aerobic sequencing batch biofilm reactor (SBBR) and the aerobic SBR reactor, respectively. A granular activated sludge with excellent settleability ðSVI ¼ 98 AE 31 L mg À1 Þ developed only in the anoxic/aerobic SBR, compared to a bulky sludge with poor settling characteristics in the aerobic SBR and SBBR. While all reactors had very good COD removal (490%) and displayed nitrification, substantial nitrogen removal (74%) was only achieved in the anoxic/aerobic SBR. During the entire operational period, benzoate, theophylline and 4-chlorophenol were completely removed in all reactors. In contrast, effluent 3-nitrobenzoate was recorded when its influent concentration was increased to 5 mg L À1 and dropped only to below 1 mg L À1 after 300 days of operation. The competent (active) biomass fractions for these compounds were between 0.04% and 5.52% of the total biomass inferred from substrate-specific microbial enumerations. The measured competent biomass fractions for 4-chlorophenol and 3-nitrobenzoate degradation were significantly lower than the influent COD fractions of these compounds. Correspondent to the highest competent biomass fraction for benzoate degradation among the test SOCs, benzoate oxidation could be quantified with an extant respirometric technique, with the highest specific oxygen uptake rate (SOUR benzoate , 0.026 g O 2 h À1 g À1 XCOD) in the anoxic/aerobic SBR. These combined results suggest that operating SBRs with alternative anoxic/aerobic cycles might facilitate the formation of granular sludge with good settleability, and retain comparable removal of nitrogen and synthetic organic compounds. Hence, the practice of anoxic/aerobic cycling should be considered in wastewater treatment systems whenever possible. r
Applied Biochemistry …, 2006
The performance of an anaerobic sequencing batch reactor (ASBR) was assessed when submitted to increasing organic load with different influent concentrations and cycle lengths. The 5-L mechanically stirred (75 rpm) ASBR contained 2 L of granular biomass and treated 2 L of synthetic wastewater per cycle. Volumetric organic loads (VOLs) from 0.66 to 2.88 g of chemical oxygen demand (COD)/(L•d) were applied by using influent concentrations from 550 to 3600 mg of COD/L in 8-and 12-h cycles. Reactor stability was maintained for VOLs from 0.66 to 2.36 g of COD/(L•d), with organic matter removal efficiencies for filtered samples (ε F) between 84 and 88%. For VOLs from 0.78 to 2.36 g of COD/(L•d) at an influent concentration of 2000 mg of COD/L, when cycle length was reduced from 12 to 8 h, ε F did not vary, yet showed a very distinct behavior from the other conditions. In addition, two operation strategies were studied for VOLs with approximately similar values of 2.36 and 2.08 g of COD/(L•d). One involved operation with an influent concentration of 2000 mg of COD/L and an 8-h cycle, whereas the other 172 Chebel et al.
THE STUDY OF NUTRIENT BALANCE IN SEQUENCING BATCH REACTOR WASTEWATER TREATMENT
The Sequencing Batch Reactor (SBR) is very suitable system for combined wastewater treatment of organic compounds and nutrient removal. Reactor can work at different conditions such as anaerobic, anoxic or aerobic. The objective of our research work was to study the influence of phosphorus concentration on N removal in a SBR wastewater treatment at various COD:N:P ratios. The results showed that the removal of N was not dependent on initial P concentration, but P removal was related to P concentration in the original wastewater. All experiments were carried out with synthetic wastewater to which different amounts of P were added. The optimal COD:N:P ratio was 100:11:2 and the BOD5:N:P ratio was 100:15:2.6.
A sequencing batch reactor (SBR) with a working volume of 8 L and an exchange ratio of 25% was used to enrich biomass for the treatment of the anaerobically treated low pH palm oil mill effluent (POME). The influent concentration was stepwise increased from 5000 ± 500 mg COD/L to 11,500 ± 500 mg COD/L. The performance of the reactor was monitored at different organic loading rates (OLRs). It was found that approximately 90% of the COD content of the POME wastewater was successfully removed regardless of the OLR applied to the SBR. Cycle studies of the SBR show that the oxygen uptake by the biomass while there is no COD reduction may be due to the oxidation of the storage product by the biomass. Further, the growth kinetic parameters of the biomass were determined in batch experiments using respirometer. The maximum specific growth rate (m max ) was estimated to be 1.143 day À1 while the half saturation constant (K s ) with respect to COD was determined to be 0.429 g COD/L. The decay coefficient (b D ) and biomass yield (Y) were found to be 0.131 day À1 and 0.272 mg biomass/mg COD consumed, respectively.
Anaerobic prefermentation and primary sedimentation of wastewater in a sequencing batch reactor
Water Sa, 2007
This research was carried out with the aim of evaluating the solubilisation and acidification capacity of fermenting organisms in suspension in a sequencing batch reactor (SBR), which had a volume of 1 800 ℓ. Using 8 h cycles with 340 min of anaerobic reaction time, the wastewater fed to the SBR presented an average of total and dissolved COD of 315 and 230 mg/ℓ. The experiment was divided into three phases: In Phase 1 the organic load was decreased from 1.46 to 0.27 kgCOD/kgTSS•d, as total COD, during a period of 154 d. If the acidification is defined as the fraction of organic substrate that is transformed to volatile fatty acids (VFA) then the highest acidification percentage (80%) of the dissolved COD (COD D) was obtained for the organic load runs of between 0.62 and 0.72 kgCOD/kgTSS•d. Within this range of organic load the 2 nd and 3 rd experimental phases were achieved at the same time after 130 d while the pH and temperature were the control parameters: pH from 5.5 to 7.5 and temperature from 22 to 31ºC. Finally, the higher production level of the dissolved COD during the fermentative reaction period was 35 mg/ℓ. The acidification of the dissolved influent COD was increased from 50 to 60% by decreasing the pH from 7.0 to 5.5 and this percentage was doubled from 33 to 66% when the temperature was increased from 22 to 31ºC. All of the dissolved effluent COD was in the form of VFA, when an organic load of 0.62 kgCOD/kgTSS•d was used or when the temperature was increased up to 31ºC. The VFA production rate that was achieved after 80 min diminished by half when the solids retention time (SRT) was decreased from 8 to 2 d or when the temperature was lowered from 31 to 24ºC.
Process Biochemistry, 2005
A sequencing batch reactor (SBR) has certain advantages over conventional activated sludge processes (ASP) for the treatment of complex wastewater. The performance of a sequencing batch reactor in treating complex chemical effluents was investigated with a suspended biomass configuration and operating under aerobic conditions. A total sequence of 24 h (15 min: filling phase; 23 h: reaction phase (aeration with recirculation); 30 min: setting; and 15 min: withdrawal) was employed and studied with various organic loading rates (1.0 kg COD/m3/day: 1.7 kg COD/m3/day and 3.5 kg COD/m3/day). The SBR performance was assessed by means of carbon removal and operational parameters such as pH, oxidation–reduction potential (ORP), sludge volume (SV), sludge volume index (SVI), suspended solids (SS) and volatile suspended solids (VSS), which were monitored during reactor operation. The SBR showed relatively more efficient performance over conventional suspended growth systems. About 8% sulphate was removed under anoxic conditions at all the studied organic loading rates. Enhanced performance with SBR over conventional ASP may be due to enforced short term unsteady state conditions coupled with periodic exposure of the microorganisms (physiological state) to defined process conditions which facilitate the required metabolic conditions for treating complex chemical effluents.
Effect of Sludge Retention Time on Treating High Load Synthetic Wastewater Using Aerobic Sequencing
The main aim of this study was to investigate the effect of sludge retention time on performance of aerobic synthetic Batch Reactor for treating a high load milk synthetic wastewater. For this purpose, four lab-scale sequencing batch reactors were operated under aerobic conditions with the same conditions at different sludge retention times (SRTs), feeding by high load milk synthetic wastewater. Operating volume, influent flow rate and influent organic loading rate for all reactors were adjusted to 5.5 L, 3.5 L/d and 1400 gCOD/m 3 d, respectively. The average effluent COD for reactor 1 to 4 with SRT of 5, 10, 15 and 20 d were 108, 97, 91 and 84 mg/L, respectively. COD removal was 94.99, 95.43, 95.86 and 96.16 percent respectively and slightly changed with SRT. However, the overall trend of COD removal vs. SRT showed an increasing rate with the correlation factor (R 2) of 0.99. Reactor 2 with SRT of 10 d(SVI) had the maximum effluent TSS ave (34mg/L) and turbidity ave (5.89 mg/L) and the minimum sludge volume index (41mL/g). All reactors had SVI ave of lower than 75 mL/g and effluent turbidity ave less than 6 NTU which was lower than Iranian national discharge standards (<50 NTU). SRT had directly influenced the biomass concentration, as the MLSS ave of reactor 1 to 4 were found to be 1824, 2694, 3210 and 3864 mg/L respectively. Best performance (minimum effluent COD, TSS and turbidity) was occurred in reactor 4 with SRT of 20 d.