Experimental Validation of the Static Granular Bed Reactor for Industrial Waste Anaerobic Treatment

The static granular bed reactor (SGBR) is a unique high-rate anaerobic reactor designed to operate in a simple downflow manner, offering high chemical oxygen demand (COD) removal efficiencies (greater than 90%) resulting from high biomass retention in the system. A study was performed to evaluate the SGBR versus a control system, the upflow anaerobic sludge blanket (UASB) reactor, and to evaluate performance idiosyncrasies of the SGBR and the control. The two reactors were operated at three different hydraulic retention times (HRTs): 8, 16, and 24 h. The reactors treated synthetic wastewater, intended to simulate food industry waste, composed of sucrose and nonfat dry milk. Overall, COD removal was higher for the SGBR than for the UASB reactor. In particular, at a HRT of 8 h, the SGBR achieved a COD removal of 90.7% and the UASB reactor reduced the COD concentration by 77.5%. The UASB reactor’s specific COD loading factor proved rate limiting with values ranging from 0.19 to 0.94?gCOD/(gVS?d) versus 0.11 to 0.34?gCOD/(gVS?d) for the SGBR. A tracer study idealized hydraulics within the two systems, and the results showed minimal dead volume and 4–6% short circuiting for both reactors.     

Enhancement of Denitrification in Upflow Sludge Bed Reactors with Sludge Wasting

From the performance data of the upflow sludge bed (USB) reactors (with sufficient carbon), the rate-limiting step in denitrification is nitrate reduction. Biological denitrification in the USB reactors (superficial velocity=0.5, 1.0, 2.0, and 4.0 m/h) can be greatly enhanced with sludge wasting from the bioreactor [i.e., maintain granular sludge retention time (GSRT) at 20 days], including high volumetric loading rates of up to 6.61 g NO3?–N/L day, high specific denitrification rates [arithmetic mean=0.31–0.42 g NO3?–N/g volatile suspended solids (VSS) day], high denitrification efficiencies (97.6–97.8%), and relatively low washout rates of biomass granules (arithmetic mean ω?=0.13–0.31 g VSS/L day). The biomass concentration, average granule size (dp), and microbial density of the USB reactors with sludge wasting were greater than those of the USB reactors without sludge wasting (i.e., the former grew more compact granules than the latter). From the granulation experiment, the granule size distribution and dp of the broken-up granules in the sludge-bed zone can restore to those of the original granules in one GSRT, implying that spontaneous flocculation of extra-cellular polymer of denitrifying-bacteria cells occurred in the USB reactor, which may also be accelerated by a rigorous backing-mixing effect of continuous production of biogas. Accordingly, the USB reactor with sludge wasting can be regarded as a promising alternative to treat high-strength nitrate wastewater.     

Nitrate Removal in Sulfur: Limestone Pond Reactors

The feasibility of using sulfur:limestone autotrophic denitrification (SLAD) pond reactors to treat nitrate-contaminated water or wastewater after secondary treatment was investigated with four lab-scale continuously fed SLAD ponds. The start-up period, temperature effects, and effects of different feed solutions were evaluated. With an influent concentration of 30 mg NO3?–N/L at an HRT of 30 days, the pond reactors had an overall nitrate removal efficiency of 85–100%. Effluent nitrite concentrations were <0.2 mg N/L in all tests. Aerobic conditions could result in a decrease of the SLAD pH of the pond by 2 to 3 units and a large increase in sulfate production ( ～ 1600–1800?mg-SO42?/L). Under unmixed (anoxic) conditions, the pH and sulfate produced were maintained at approximately 5.5 to 5.6 and 400–600?mg-SO42?/L, respectively, in all the SLAD ponds. Temperature affected the pond reactors adversely. By assuming that a first-order reaction occurred in a SLAD pond reactor, the temperature-activity coefficient, θ was found to be 1.068. Treatment of nitrate-contaminated surface water and wastewater using SLAD pond systems is feasible only if (1) the chemical oxygen demand (COD)/nitrate–N (COD/N) ratio is low (<1.2 with an initial NO3? concentration of 30 mg-N/L), (2) sulfur:limestone granules are not covered by sediment, and (3) sulfur-utilizing but nondenitrifying bacteria (SUNDB) are greatly inhibited due to the lack of DO in the pond systems. The SLAD ponds are not feasible for the treatment of raw wastewater or surface water if they contain high concentrations of organic matters due to the possible inhibition of sulfur-based autotrophic denitrifiers by heterotrophs (including heterotrophic denitrifiers). In addition, a high sulfate and low DO concentration as well as a low pH in the SLAD effluent of the pond (even when the pond is operated in an unmixed mode) also will limit the application of SLAD pond processes.     

2,4,6 Tri-Chlorophenol Containing Wastewater Treatment Using a Hybrid-Loop Bioreactor System

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with an effluent recycle was used for biological treatment of 2,4,6 tri-chlorophenol (TCP) containing synthetic wastewater. The effects of sludge age (solids retention time) on chemical oxygen demand (COD), TCP, and toxicity removal performance of the system were investigated for sludge ages between 5 and 30?days, while the feed COD (2600±100?mg?L?1), TCP (370±10?mg?L?1), and the hydraulic residence time (25?h) were constant. Percent TCP, COD, and toxicity removals increased with increasing sludge age resulting in nearly complete COD, TCP, and toxicity removal at sludge ages above 20?days. Biomass concentrations in the packed column and in the aeration tank increased with increasing sludge age resulting in low reactor TCP concentrations, and therefore, high TCP, COD, and toxicity removals. More than 95% of COD, TCP, and toxicity removal took place in the packed column reactor. Volumetric rates of TCP and COD removal increased due to increasing biomass and decreasing effluent TCP and COD concentrations with increasing sludge age. The specific rate of TCP removal was maximum (120?mg?TCP?gX?1?day?1) at a sludge age of 20?days. TCP inhibition was eliminated by operation of the system at sludge age above 20?days to obtain nearly complete COD, TCP, and toxicity removal.     

Combined System for Biological Removal of Nitrogen and Carbon from a Fish Cannery Wastewater

A combined system composed of three sequentially arranged reactors, anaerobic-anoxic-aerobic reactors, was used to treat the wastewater generated in the tuna cookers of a fish canning factory. These wastewaters are characterized by high chemical oxygen demand (COD) and nitrogen concentrations. The anaerobic process was performed in an upflow anaerobic sludge blanket reactor operated in two steps. During Step I different influent COD concentrations were applied and organic loading rates (OLRs) up to 4 g COD/(L?d) were achieved. During Step II hydraulic retention time (HRT) was varied from 0.5 to 0.8 days while COD concentration in the influent was constant at 6 g COD/L. The OLRs treated were up to 15 g COD/(L?d). When HRTs longer than 0.8 days were used, COD removal percentages of 60% were obtained and these values decreased to 40% for a HRT of 0.5 days. The denitrification process carried out in an upflow anoxic filter was clearly influenced by the amount of carbon source supplied. When available carbon was present, the necessary COD/N ratio for complete denitrification was around 4 and denitrification percentages of 80% were obtained. The nitrification process was successful and was almost unaffected by the presence of organic carbon (0.2–0.8 g TOC/L), with ammonia removal percentages of 100%. Three recycling ratios (R/F) between the denitrification and nitrification reactors were applied at 1, 2, and 2.5. The overall balance of the combined system indicated that COD and N removal percentages of 90% and up to 60%, respectively, were achieved when the R/F ratio was between 2 and 2.5.     

Combined Anaerobic/Aerobic Secondary Municipal Wastewater Treatment: Pilot-Plant Demonstration of the UASB/Aerobic Solids Contact System

Anaerobic pretreatment followed by aerobic posttreatment of municipal wastewater is being used more frequently. Recent investigations in this field using an anaerobic fluidized bed reactor/aerobic solids contact combination demonstrated the technical feasibility of this process. The investigation presented herein describes the use of a combined upflow anaerobic sludge bed (UASB)/aerobic solids contact system for the treatment of municipal wastewater and attempts to demonstrate the technical feasibility of using the UASB process as both a pretreatment unit and a waste activated sludge digestion system. The results indicate that the UASB reactor has a total chemical oxygen demand removal efficiency of 34%, and a total suspended solids removal efficiency of about 36%. Of the solids removed by the unit, 33% were degraded by the action of microorganisms, and 4.6% accumulated in the reactor. This low solids accumulation rate allowed operating the UASB reactor for three months without sludge wasting. The long solids retention time in this unit is comparable to the one normally used in conventional sludge digestion units, thus allowing the stabilization of the waste activated sludge returned to the UASB reactor. Particle flocculation was very poor in the UASB reactor, and therefore, it required postaeration periods of at least 100?min to proceed successfully in the aerobic unit. Polymer generation, which is necessary for efficient biological flocculation, was practically nonexistent in the anaerobic unit; therefore, it was necessary to maintain dissolved oxygen levels greater than 1.5?mg/L in the aerobic solids contact chamber for polymer generation to proceed at optimum levels. Once these conditions were attained, the quality of the settled solids contact chamber effluent always met the 30?mg BOD/L, 30?mg SS/L secondary effluent guidelines.     

Low-Strength Wastewater Treatment with Combined Granular Anaerobic and Suspended Aerobic Cultures in Upflow Sludge Blanket Reactors

Combined cultures were developed from anaerobic granular and suspended aerobic cultures in three upflow sludge blanket reactors aerated at 10?mL air/min 4?h/day (R2), every other day (R3), and 24?h/day (R4). The use of combined cultures was found to be advantageous compared to the anaerobic granules for the treatment of low-strength wastewaters. During municipal wastewater treatment at influent 5-day biochemical oxygen demand (BOD5) concentration of 53–118?mg/L (hydraulic retention time: 0.75?day), combined cultures in R2, R3, and R4 exhibited average BOD5 removal efficiencies of 52, 75, and 76%, respectively. The use of these cultures might be proposed as an alternative for municipal wastewater treatment due to their advantages such as achievement of required discharge standards, prevention of biomass loss/settleability problems unlike activated sludge systems and possible methanogenic activity, as well as high settling characteristics comparable to those of anaerobic granules.     

Treatment of Landfill Leachate by a Combined Anaerobic Fluidized Bed and Zeolite Column System

The use of a combined anaerobic fluidized bed and zeolite fixed bed system in sanitary landfill leachate treatment was investigated. Anaerobic treatability studies were successfully performed in the anaerobic fluidized bed reactor. The chemical oxygen demand (COD) removal was attained up to 90% with increasing organic loading rates as high as 18?g?COD/L?day after 80?days of operation. Good biogas production yield (Ygas) of 0.53?L biogas per gram removed COD with methane (CH4) content of 75% was obtained. The attached biomass concentration increased along the column height from bottom to top, and its mean value was found 6,065?mg/L after 100?days of operation. The anaerobically treated landfill leachate was further treated by a zeolite fixed bed reactor. While excellent ammonia removal (>90%) was obtained with the untreated zeolite, the regenerated zeolites showed higher performance. Consequently, this combined anaerobic and adsorption system is an effective tool to remove high COD and high ammonia in landfill leachate.     

Fate of Tolyltriazoles and Nonylphenol Ethoxylates in Upflow Anaerobic Sludge Blanket Reactors

The fate of tolyltriazoles, nonylphenol and nonlyphenol ethoxylates during anaerobic treatment of ethylene glycol (EG) based wastewater during batch or continuous upflow anaerobic sludge blanket reactors was investigated. Equilibrium sorption studies indicated that there was minimal sorption of benzotriazole (BT), 5-methyl-1 H-benzotriazole (MeBT), and 5,6-dimethyl-1 H-benzotriazole (DiMeBT) to anaerobic granules. Nonylphenol (NP), a reported biodegradation product of NP ethoxylates, had a higher sorption capacity to anaerobic biomass and was described by the Freundlich isotherm. Batch serum bottle EG degradation experiments indicated that BT, MeBT, DiMeBT, and the nonionic NP ethoxylate surfactant Tergitol NP-4 had no significant effects on acidogenesis and methanogenesis at the concentration levels studied. Significant inhibition of acetoclastic activity was observed for the biodegradation intermediate NP at 100?mg/L, with acetic acid consumption rate at 38% of the controls. No evidence for anaerobic degradation of benzotriazole and its derivatives was observed for both batch and continuously fed anaerobic systems. Continuously fed anaerobic experiments provided evidence that indicated that anaerobic degradation of nonylphenol ethoxylates and the biodegradation intermediate NP occurred.     

Simultaneous Nitrogen and Phosphorus Removal from High-Strength Industrial Wastewater Using Aerobic Granular Sludge

Aerobic granular sludge technology was applied to the simultaneous nitrogen and phosphorus removal from livestock wastewater that contains high concentrations of nitrogen and phosphorus (TN: 650?mg/L; TP: 125?mg/L). A lab-scale sequencing batch reactor was operated in an alternating anaerobic/oxic/anoxic denitrification mode. Granular sludge was first formed using synthetic wastewater. When livestock wastewater was diluted with tap water, the shape and settleability of aerobic granular sludge were maintained even though livestock wastewater contained suspended solids. Simultaneous nitrification, denitrification, and phosphate uptake were observed under an aerobic condition. However, when nondiluted livestock wastewater was used, the diameter of granular sludge and the denitrification efficiency under an oxic condition decreased. When the concentrations of nitrogen and phosphorus in wastewater increased, hydraulic retention time (HRT) increased resulting in a decrease in selection pressure for granular sludge. Therefore, the sustainment of granular sludge was difficult in livestock wastewater treatment. However, by applying a new excess sludge discharge method based on Stokes’ law, the shape of granular sludge was maintained in spite of the long HRT (7.5?days). To select large granular sludge particles, excess sludge was discharged from the upper part of settled sludge because small particles localized there after settling. Finally, excellent nitrogen and phosphorus removal was accomplished in practical livestock wastewater treatment. The effluent concentrations of NH4–N, NOx–N, and PO4–P were <0.1, 1.4, and 1.2?mg/L, respectively.     

Biotransformation of Carbon Tetrachloride and Anaerobic Granulation in a Upflow Anaerobic Sludge Blanket Reactor

Carbon tetrachloride (CT) in a synthetic wastewater was effectively degraded in a 2?l upflow anaerobic sludge blanket reactor during the granulation process by increasing the chemical oxygen demand (COD) and CT loadings. The effect of operational parameters such as influent CT concentrations, COD, CT loading, food to mass (F/M) ratio, and specific methanogenic activity (SMA) were also detected during granulation. Over 97% of CT was removed at 37°C, at a COD loading rate of 10?g/L?day. Chemical oxygen demand and CT removal efficiencies of 92 and 88% were achieved when the reactor was operating at CT and COD loading rates of 17.5?mg/L?day and 12.5?g/L?day, respectively. This corresponds to an hydraulic retention time of 0.28?day and an F/M ratio of 0.57?g?COD/g?volatile?suspended?solids?(VSS)?day. In 4?weeks, the seed sludge developed the CT degrading capability that was not very sensitive to shocks. The granular sludge cultivated had a maximum diameter of 2.5?mm and SMA of 1.64?g?COD/g?VSS?day. Glucose biodegradation by CT acclimated anaerobic granules was expressed with competitive inhibition. However the competitive inhibition was not significant since the competitive inhibition coefficient (Ki) was as high as 18.72?mg/L. Kinetic coefficients of k (maximum specific substrate utilization rate), Ks (half velocity coefficient), Y (growth yield coefficient), and b (decay coefficient) were determined as 0.6/day, 1.1?mg/L, 0.23?g?VSS/g glucose-COD, and 0.01/day, respectively, based on growth substrate glucose–COD during CT biotransformation. The CT was treated via biodegradation and this contributed to 89% of the total removal. The removal contributions from biomass adsorption, abiotic transformation, and volatilization were negligible. Adsorption and volatilization accounted for only 0.8 and 0.5% of the total removal, respectively.     

Potential of a Combination of UASB and DHS Reactor as a Novel Sewage Treatment System for Developing Countries: Long-Term Evaluation

A novel municipal wastewater treatment system, consisting of a combination of an upflow anaerobic sludge blanket (UASB) and down-flow hanging sponge (DHS) posttreatment unit, was continuously evaluated for more than three years with raw sewage as an influent. The system was installed at a sewage treatment site and operated at 25±3°C. This paper reports on the results of a long term monitoring of the system. The whole experimental period was divided into three distinct phases with different operating conditions. Organic pollutants were only partially removed in anaerobic UASB pretreatment unit. The remaining organics as well as nitrogenous compounds were almost completely removed by the DHS posttreatment unit. In all phases the system demonstrated removal efficiency consistently over 95% for unfiltered biochemical oxygen demand (BOD), 80% for unfiltered-chemical oxygen demand and 70% for suspended solids. The system produced an excellent effluent quality with only 4–9?mg/L of residual unfiltered BOD. Dissolved oxygen in the final effluent was 5–7?mg/L although no aeration was provided to DHS system. Moreover, excess sludge production from DHS was negligible thus eliminating secondary sludge that is troublesome to dispose off. The system also exhibited substantial stability against twofold hydraulic shock load and fourfold organic shock load. The results suggested that the proposed system may be a competitive solution for municipal sewage treatment under variable conditions.     

Improved Anaerobic Process Efficiency Using Mesophilic and Thermophilic Elutriated Phased Treatment

An innovative anaerobic digestion elutriated phased treatment (ADEPT) has been evaluated at mesophilic (M-ADEPT) (35°C) and thermophilic (T-ADEPT) (55°C) temperatures in which the organic loading rate (OLR) was increased until reactor failure (pH<5.5). Single-stage continuously stirred tank reactors (CSTRs) at both temperatures were also operated as controls (M-CSTR for 35°C and T-CSTR for 55°C). The T-CSTR failed at an OLR of 7.4 g volatile solid (VS)/L?day and the M-CSTR at an OLR of 10 g VS/L?day while the M-ADEPT continued until an OLR of 18 g VS/L?day and the T-ADEPT reached an OLR of 24 g VS/L?day before system failure. The T-CSTR produced the poorest effluent quality as manifested by high propionate concentrations (1,500–2,500 mg/L) while both M-ADEPT and T-ADEPT produced much better quality of effluent with propionate concentrations below 100 mg/L. Thus it appears that the T-ADEPT design may solve effluent quality problems associated with normally high propionate concentrations produced during thermophilic anaerobic digestion. Superior effluent quality, reduced reactor volume requirements, more stable methanogenesis due to the extended solids retention time, and uncoupling of the methanogen wasting from the refractory sludge wasting process resulted in stable and efficient processing at both temperatures for the innovative ADEPT design. Because the higher amounts of volatile fatty acids produced in the acid elutriation phase of the ADEPT system can be a favorable carbon source for biological nutrient removal in wastewater treatment plants, this positive aspect should be considered in future applications of the ADEPT system.     

Effects of Sodium Chloride on the Performance of a Sequencing Batch Reactor

In this study, we investigated the effects of sodium chloride (concentrations ranging from 0?to?60?g/L) on the performance of sequencing batch reactors (SBRs) using a microbial culture developed from a domestic sewage treatment plant. The lab-scale SBRs were fed with synthetic wastewater (acetate as the organic substrate) containing either sodium chloride solution or seawater to ensure consistency in feed composition. It was found that sodium chloride concentrations of up to 10?g/L stimulated substrate removal. The organic removal efficiency decreased from 96%, when no sodium chloride was added, to 86% when 60?g/L of sodium chloride was introduced into the influent wastewater. Effluent turbidity increased significantly when the sodium chloride concentration in the wastewater was equal to or above 30?g/L even though the sludge volume index (SVI) decreased. The increase in effluent turbidity could be caused by the release of nondissolved cellular components due to plasmolysis of microorganisms as observed by scanning electron microscopy. Experiments involving seawater (with 20?g/L total dissolved solids) showed that organic removal efficiency improved from 87 to 95% while effluent turbidity and SVI values were lowered when the loading rate parameter (Li) was lowered from 0.6?to?0.3?mg total chemical oxygen demand (mg?VSS?day). Optical microscopy and scanning electron microscopy indicated morphological changes in the microbial population. From this study, it was concluded that microbial culture from domestic wastewater facilities could be acclimated in a SBR to treat wastewater containing sodium chloride concentrations of up to 60?g/L.     

Role of Particle Size and Ammonium Oxidation in Removal of 17α-Ethinyl Estradiol in Bioreactors

Laboratory scale bioreactors were used to investigate sorption and biodegradation of 17α-ethinylestradiol (EE2). EE2 is among many emerging micropollutants that may cause endocrine disruption of aquatic organisms in the environment. Results showed that the sludge taken from the membrane bioreactor (MBR) had a sorption distribution coefficient that was more than twice that of biomass derived from sequencing batch reactors (SBRs). The MBR biomass had smaller particles and was more hydrophobic than the SBR biomass. Experiments with nitrifying sludge showed that sorption was more important when the initial ammonia concentration was 48?mg/L or less, but at higher initial ammonia concentrations the role of biodegradation became more important. The ammonium monooxygenase enzyme extracted from a nitrifying mixed culture removed EE2 in batch experiments. These findings are the first that we are aware of to link biomass particle size, hydrophobicity, and sorption capacity. These results also support the notion that cometabolic biodegradation of EE2 can occur in nitrifying sludge.     

Cell Immobilized FOG-Trap System for Fat, Oil, and Grease Removal from Restaurant Wastewater

Cell immobilized lipase-producing bacteria on three different matrices were incorporated in a fat-, oil-, and grease (FOG) trap system for restaurant wastewater treatment. During a 16-day laboratory-scale experiment for the treatment of synthetic FOG wastewater containing soybean oil, no significant difference (two-tailed t test at 95% confidence interval) in the FOG removal between two systems was observed at FOG influent ≤ 1,000?mg/L. However, the typical trap showed lower FOG removal efficiency than the matrix-based system when the influent FOG concentration was increased to ≥ 5,000?mg/L. In addition, the matrix-based trap system was able to sustain a stable high FOG removal, with <100?mg/L effluent, even at 10,000 mg/L influent FOG. Based on FOG heights measured and mass balance calculations, 97.4 and 99.5% of the total FOG load for 16 days were removed in a typical trap and matrix-based system, respectively. About 93.6% of the removal in the matrix-based was accounted to biodegradation. The 30-day full-scale operations demonstrated a distinguishably better performance in the matrix-based system (92.7±9.06% of 1,044.8±537.27?mg FOG/L) than in the typical trap system (74.6±27.13% of 463.4±296.87?mg FOG/L) for the treatment of barbeque restaurant wastewater. Similarly, matrix-based system revealed higher chemical oxygen demand removal (85.9±11.99%) than the typical trap system (60.4±31.26%). Characterizations of the influent, emulsified, adsorbed and effluent FOG indicated that straight saturated fatty acids constituted the cause of clogging problems in the FOG-trap and piping system.     

Treatment of High-Strength Pharmaceutical Wastewater and Removal of Antibiotics in Anaerobic and Aerobic Biological Treatment Processes

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.     

Simultaneous Nitrogen and Phosphorus Removal Using a Double Sludge Switching Sequencing Batch Reactor

A new process using a sequencing batch reactor (SBR) and two smaller sludge hoppers is proposed for the simultaneous removal of phosphorus and nitrogen from wastewater. In the double sludge switching sequencing batch reactor, denitrifying phosphate accumulating bacteria (DPB) sludge and nitrification sludge are transferred to the SBR at different phases instead of flowing wastewater through different reactors. The process was operated with a cycle time of 10.5?h, consisting of DPB sludge filling phase (0.5?h), anaerobic phase I (2.0?h), settling and changing DPB sludge phase (0.5?h), anaerobic phase II (0.5?h), aerobic phase (4.0?h), settling and changing nitrifying sludge phase (0.5?h), and anoxic phase (3.0?h). Results of stable operation showed that the process was very efficient over a range of temperatures varied from 10?to?28°C. The average effluent concentrations and removal efficiencies were as follows: CODCr 28.0?mg/L, 92.1%; BOD5 7.0?mg/L, 95.1%; NH3–N 0.8?mg/L, 98.0%; TN 9.8?mg/L, 76.7%; and TP 0.5?mg/L, 92.3%.     

Granular Bed Baffled Reactor (Grabbr): Solution to a Two-Phase Anaerobic Digestion System

A single unit anaerobic granular bed baffled reactor (GRABBR) is proposed as an alternative to a separately operated two-phase anaerobic digestion system. This overcomes the problems related to wastewater treatment at high loading rates which usually results in accumulation of intermediate acid products, and consequently inhibits methanogenesis. This study was carried out to evaluate the stability of a five compartment GRABBR system when treating synthetic glucose wastewater at various operational conditions. The reactor was started with volumetric organic loading rate (OLR) of 1 kg chemical oxygen demand (COD)/m3?day, equivalent to 120 h hydraulic retention time (HRT), and loading rates were gradually increased at suitable intervals to up to 20 kg COD/m3?day (6 h HRT). At steady state, the overall soluble COD (SCOD) removal was over 95% under all applied loading conditions. At lower loadings, the reactor operated as a completely mixed system, and most of the treatment was achieved in the first compartment. At higher loadings, the entire system transformed into different phases, acidogenesis being dominant near the influent point, whilst methanogenesis was the main activity in the compartments near the effluent point. Granule breaking and flotation was observed in the acidogenic zone, whilst the methanogenic zone retained its original granular form. High assimilation rate of influent nitrogen was observed in the first compartment with the formation of nongranular biomass, identified as Klebsiella pneumoniae. The success of GRABBR as a single unit two-phase anaerobic digestion system could save the cost of an extra unit traditionally employed to achieve similar goals in treatment of high strength wastewaters.     

Comparison of Steroid Hormone Concentrations in Domestic and Hospital Wastewater Treatment Plants

Influent and effluent samples originating from two wastewater treatment plants (WWTPs) (treating hospital wastewater and domestic wastewater, Belgium) have been analyzed in order to estimate their steroid hormone content. The natural estrogens estrone (E1), 17β-estradiol (E2), and the synthetic 17α-ethinylestradiol (EE2) together with other steroid hormones progesterone (P) and testosterone (T) metabolites were detected in these samples. The hormone concentrations in both the hospital and the domestic WWTP samples were not significantly different and ranged from <0.2?ng EE2/L to 114?ng EE2/L, from <0.2?ng E1/L to 58?ng E1/L and from <0.2?ng P/L to >100?ng P/L. E2 was detected once at a concentration of 17?ng/L. In the domestic WWTP which comprises a conventional activated sludge treatment in parallel with a membrane bioreactor, no differences in estrogen removal efficiency could be observed for both treatments. In comparison to chemical analysis data, the Yeast Estrogen Screen (YES) appears to underestimate the influent estrogen concentrations, probably due to influent toxicity for the YES. Effluent estrogen concentrations, on the other hand, were overestimated by the YES test, probably due to the presence of other estrogenic compounds in the effluent.