Comparative Study between a Hybrid System and a Biofilm System for the Treatment of Ammonia and Organic Matter in Wastewaters

The efficiency of two similar gas-lift bioreactors, a biofilm reactor and a hybrid circulating floating bed reactor (CFBR), were studied and compared. In the biofilm CFBR the biomass grew preferably adhered on a plastic granular support, whereas in the hybrid CFBR both suspended biomass and biofilms were allowed to grow in the reactor. COD/NH4+ ratio (COD=chemical oxygen demand) was manipulated between 0.0 and 8.0?g/g, maintaining the ammonia influent concentration around 50?mg N–NH4+/L, the ammonia loading rate at 0.9?kg N–NH4+/m3?day and the hydraulic retention time at 1.36?h. At low COD/NH4+ ratio (0 and 0.5?g/g) both systems behaved similarly, achieving ammonia removal percentages higher than 95%. In the biofilm CFBR a reduction of the nitrification percentage from 95 to 20% was observed when a COD/N–NH4+ ratio up to 8?g/g was applied in the influent. However, at the same operational conditions, the nitrification process in the hybrid CFBR was slightly affected. In the hybrid-CFBR reactor heterotrophs growing in suspension consumed the COD source faster than those growing in biofilms as was monitored. The growth of heterotrophic microorganism in suspension had a beneficial effect for the nitrifying population growing in the biofilm of the hybrid CFBR. Nitrifying activity of the biofilm was not limited by the presence of heterotrophs consuming dissolved oxygen, displacing the nitrifying bacteria or creating mass transfer resistance as was observed in the biofilm CFBR.     

Simultaneous Removal of Nitrogen and Phosphorous from Municipal Wastewater Using Continuous-Flow Integrated Biological Reactor

A pilot-scale experiment was carried out to study the simultaneous removal of nitrogen and phosphorous from municipal wastewater by an innovative continuous-flow integrated biological reactor (CIBR) process. A three-phase separator was used in the CIBR process, which not only saved energy consumption of sludge returning, but also solved the sludge–gas separating problem. The optimal working condition was 2?h aeration, 1?h agitation, and 1?h settling, with an energy consumption of 0.23?kW?h/m3. The average removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), total nitrogen (TN), and total phosphorus (TP) under the optimal conditions were 72.87, 75.23, 61.25, and 68.25%, respectively. The distributing rules of dissolved oxygen, pH, mixed liquid suspended solid, COD, NH4+–N, NO3?–N, TN, and TP in each phase of CIBR was studied. It was indicated that the appropriate condition was created for the simultaneous removal of nitrogen and phosphorus in the integrated reactor. The study demonstrated the feasibility of using CIBR process for simultaneous removal of nitrogen and phosphorus at the average temperature 12.2°C.     

Optimization of Biological Nutrient Removal in a Membrane Bioreactor System

The main objective of the present study is to develop a modified membrane bioreactor (MBR) system for the treatment of municipal wastewater for the enhanced biological removal of nitrogen (N) and phosphorus (P) simultaneously with the ultimate goal of optimizing the two processes. The paper will address the implementation and optimization of the MBR process with respect to biological characteristics, operational performance, and effluent quality. The system utilizes anoxic P uptake and nitrification–denitrification in a MBR. Following optimization, the system achieved 99% chemical oxygen demand (COD), 98.4% NH3–N, 77.5% TN, and 96.3% P removal producing effluent biological oxygen demand, COD, NH3–N,NO3–N,NO2–N, and P of <3, 3, 0.4, 5.8, 0.050, and 0.18?mg/L, respectively.     

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.     

Single-Submerged Attached Growth Bioreactor for Simultaneous Removal of Organics and Nitrogen

The use of a single-unit, single-zone submerged attached growth bioreactor (SAGB) for the combined removal of carbonaceous organics and nitrogen from a municipal wastewater was demonstrated. A nitrification efficiency of 97% was achieved at a total organic loading of 3.47?kg?bCOD/m3?day. The total nitrogen loading varied from 0.2?to?0.3?kg?N/m3?day and resulted in effluent total nitrogen concentrations ranging from 4.2?to?8.5?mg/L. Concurrent denitrification was achieved at rates ranging from 0.077?to0.29?kg?N/m3?day. This single-unit SAGB, by providing dual treatment capacities, represents a cost-effective option that is particularly attractive for facilities with limited space and budget for system upgrade.     

Effect of Dynamic Loading on Biological Nutrient Removal in a Pilot-Scale Liquid-Solid Circulating Fluidized Bed Bioreactor

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was employed for biological nutrient removal from municipal wastewater at the Adelaide Pollution Control Plant, London, Ontario, Canada. Lava rock particles of 600?μm were used as a biomass carrier media. The system generated effluent characterized by <1.0?mg NH4–N/L, <6.0?mg NO3–N/L, <1.0?mg PO4–P/L, <10?mg TN/L, and <10?mg SBOD/L at an influent flow of 5?m3/d, without adding any chemicals for phosphorus removal and secondary clarification for suspended solids removal. The impact of the dynamic loading on the LSCFB effluent quality and its nutrient removal efficiencies were monitored by simulating wet weather condition at a maximum peaking factor of 3 for 4 h. The achievability of effluent characteristics of 1.1 mg NH4–N/L, 4.6 mg NO3–N/L, 37 mg COD/L, and 0.5 mg PO4–P/L after 24 h of the dynamic loading emphasize the favorable response of the LSCFB to the dynamic loadings and the sustainability of performance without loss of nutrient removal capacity.     

Horizontal-Flow Biofilm System with Step Feed for Nitrogen Removal

The aim of this study was to develop a simple biological system suitable for the treatment of dairy parlor wash waters. A novel horizontal-flow biofilm system with step feed was designed, constructed, and tested in the laboratory for organic carbon removal, nitrification, and denitrification of a synthetic dairy wastewater with average filtered chemical oxygen demand (CODf) of 2,060?mg/L, total nitrogen (TN) of 288?mg/L, and ammonia nitrogen (NH4–N) of 127?mg/L. The novel biofilm system consisted of two reactor units placed on top of one another, each comprising a stack of horizontal plastic sheets. Part of the wastewater was pumped onto Sheet 1 (top feed) and the remainder onto Sheet 11 (step feed) and flowed over the horizontal sheets down through the system. Three hydraulic loading rates were examined: 32.3, 25.1, and 19.3?L/m2?day, based on the top plan area, and the respective removals of CODf were 96, 96, and 97% and of TN, 86, 83, and 75% were achieved. The system was simple and cheap to construct and operate.     

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.     

Operational Optimization and Mass Balances in a Two-Stage MBR Treating High Strength Pet Food Wastewater

A two-stage membrane bioreactor (MBR) system was evaluated for the treatment of high strength pet food wastewater characterized by oil and grease, chemical oxygen demand (COD), biochemical oxygen demand (BOD)5, total suspended solids (TSS), total Kjeldahl nitrogen (TKN), NH4–N, and TP concentrations of 2,800, 25,000, 10,000, 4,500, 1,650, 1,300, and 370?mg/L, respectively, to meet stringent surface discharge criteria of BOD5, TSS, and NH4–N of <10?mg/L, and TP of <1?mg/L. Pretreatment of the dissolved air flotation effluent with FeCl3 at a dose of 3.5?g/L, corresponding to a Fe:P molar ratio of 1.3:1 affected TP, TSS, volatile suspended solids (VSS), COD, BOD5, and TKN reductions of 88, 72, 75, 11, 11, 36, and 17%, respectively. The two-stage MBR operating at a total hydraulic retention time of 5.3?days comprising 2.5?days in the first stage and 2.8?days in the second stage, and solids retention time of 25?days in the first stage consistently met the criteria despite wide variations in influent characteristics. Very high COD and BOD5 removal efficiencies of 97.2 and 99.8% were observed in the first stage, with an observed yield of 0.14?gVSS/gCOD. A modular approach for the quantification of simultaneous nitrification denitrification (SND) in the first-stage MBR was developed and verified experimentally. The model indicated that on average, 21% of the influent nitrogen was removed by SND and predicted nitrogen loss with an accuracy of 72%. Complete nitrification of the residual organic nitrogen and ammonia was achieved in the second-stage MBR.     

Influence of COD:N:P Ratio on Nitrogen and Phosphorus Removal in Fixed-Bed Filter

This study examined the effects of COD:N:P ratio on nitrogen and phosphorus removal in a single upflow fixed-bed filter provided with anaerobic, anoxic, and aerobic conditions through effluent and sludge recirculation and diffused air aeration. A high-strength wastewater mainly made of peptone, ammonium chloride, monopotassium phosphate, and sodium bicarbonate with varying COD, N, and P concentrations (COD: 2,500–6,000, N: 25–100, and P: 20–50 mg/L) was used as a substrate feed. Sodium acetate provided about 1,500 mg/L of the wastewater COD while the remainder was provided by glucose and peptone. A series of orthogonal tests using three factors, namely, COD, N, and P concentrations, at three different concentration levels were carried out. The experimental results obtained revealed that phosphorus removal efficiency was affected more by its own concentration than that of COD and N concentrations; while nitrogen removal efficiency was unaffected by different phosphorus concentrations. At a COD:N:P ratio of 300:5:1, both nitrogen and phosphorus were effectively removed using the filter, with removal efficiencies at 87 and 76%, respectively, under volumetric loadings of 0.1?kg?N/m3?d and 0.02?kg?P/m3?d.     

Application of the Nitritation and Anammox Process into Inorganic Nitrogenous Wastewater from Semiconductor Factory

The first full-scale nitritation and anaerobic ammonium oxidation (Anammox) processes for an inorganic wastewater of semiconductor factory were installed and performances were evaluated. Existing facilities of conventional nitrification and denitrification were retrofitted to a combination of the nitritation and Anammox process. Novel nitritation method, selective acceleration of ammonia oxidation by high concentration of inorganic carbon, was evaluated in full-scale aeration tank with carrier material. The ammonia conversion rate of the nitritation reactor was in the range of 0.27–0.48?kg?NO2-N/m3?day after start-up period, and stable nitritation was achieved for over 10 months. In an Anammox reactor, on-site cultivation of anammox bacteria was performed, and the most plausible reason for slower nitrogen conversion at the beginning was oxygen contamination into the reactor. After minimizing influence of oxygen contamination, design loading was achieved within 3 months of operation. After start-up period, stable Anammox reactions are maintained for over 10 months. The nitrogen removal rate after start-up period was in the range of 1.04–3.29?kg?N/m3?day. In combination with conventional denitrification process, soluble nitrogen in the final effluent was reduced below 8 mg/L.     

Swine Wastewater Treatment Using Submerged Biofilm SBR Process: Enhancement of Performance by Internal Circulation through Sand Filter

Pollutants removal from swine wastewater by a submerged biofilm sequencing batch reactor (BSBR) with internal circulation of liquor through a sand filter was studied. The variation of nutrient removal efficiencies with changes in volumetric circulation ratios and rates were determined. The reactor was operated under the following conditions: One cycle per day, hydraulic retention time of 15 days, average NH4–N loading rate of 55?g?m?3?d?1, and without supplemental external carbon source. System performance was enhanced by conducting internal circulation of liquor through the sand filter. When compared with the performance of a single BSBR without sand filter, nitrogen and phosphorus removal efficiencies were found to increase by 18% and over 33%, respectively. With a circulation rate of 170?L?h?1?m?3, and duration of 22 h (circulation ratio of 0.9), TOC, NH4–N, and total soluble inorganic nitrogen (as NH4–N plus NOx–N) removal efficiencies of 73, 97.8, and 85.6%, respectively, were achieved. The enhancement of nitrogen removal was attributed to the occurrence of denitrification in the sand filter during circulation of liquor. The denitrification rate was proportional to the volumetric circulation ratio per day, resulting in an average 15% NOx–N removal in the sand filter. Also, it was found that continuous circulation during the entire reaction phases could be one way to achieve better performance.     

Effect of Organic Loading Rate on Aerobic Granulation. II: Characteristics of Aerobic Granules

Four sequential aerobic sludge blanket reactors, Reactors R1, R2, R3, and R4, were operated at organic loading rates (OLRs) of 1, 2, 4, and 8?kg chemical oxygen demand (COD)/m3?day, respectively. Aerobic granules were not detected at the low OLRs in R1 and R2. Aerobic granules first appeared on Day 14 in Reactor R3, operating at a moderate OLR of 4?kg COD/m3?day. Aerobic granules were initially observed on Day 18 in R4, operating at the highest OLR tested of 8?kg COD/m3?day. These granules were unstable and disintegrated within 2 weeks after their first appearance. Under the OLR of 4?kg COD/m3?day, the process of aerobic granulation could be clearly divided into three phases of acclimation, multiplication, and maturation, with specific granular growth rates (ν?) of 0.1081, ?0.0064, and ?0.0008?day?1, respectively. The values of ν? became smaller with time, and indicated that the aerobic granules had stabilized. Compared to the looser and more amorphous flocs, the compact granules in Reactor R3 possessed a higher specific gravity of 1.064, a higher strength with an integrated coefficient of 99.5%, a higher cell surface hydrophobicity of 75%, and a higher ratio of polysaccharides (PS) to proteins (PN) at 5.0?mg PS per mg PN.     

Combined Removal of Carbon and Nitrogen in an Integrated UASB-Jet Loop Reactor Bioreactor System

An innovative anaerobic–aerobic integrated bioreactor system consisting of an upflow anaerobic sludge blanket (UASB) and a jet loop reactor was developed to investigate the feasibility of combined removal of carbon and nitrogen for a low-strength wastewater at different hydraulic retention times (HRTs) and recycle ratios. Total chemical oxygen demand (COD) removal of the integrated system increased from 87 to 92%, at a combined system HRT of 44?h, when the recycle ratio was increased from 100 to 400%, respectively. Denitrification efficiency of the integrated system increased from 49 to 86%, at all HRTs, when the recycle ratio was increased from 100 to 400%. The integrated system, on average, achieved more than 78% of total nitrogen at all HRTs. Nitrogen content of the biogas produced from the UASB reactor increased with increase in recycle ratios while the methane content exhibited a reverse trend, irrespective of the HRTs. Sludge volume index of the UASB reactor increased from 15?to?42?mL/g total suspended solids at the end of the study. Specific methanogenic activity of the granular sludge decreased from 1.3 to 0.8 g CH4–COD/g volatile suspended solids per day at the end of the study. Nitrogen and COD mass balance of the integrated system indicated that a substantial amount of influent nitrogen and COD was lost in the effluent as dissolved form.     

UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.     

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.     

稀土矿区低碳氨氮废水短程硝化SBR过程研究

采用SBR工艺处理稀土矿区低碳氨氮废水, 对活性污泥进行驯化培养并考察了曝气量、曝气时间及碳氮比对短程硝化系统的影响。试验结果表明:温度为(28±1) ℃、曝气量为65 L/h, pH值为8的条件下, 经过69 d的驯化培养后, 系统对氨氮的去除率达92%, 亚硝态氮积累率稳定在90%以上, 对短程硝化过程启动前后样品进行高通量测序, 结果表明:污泥中微生物种类减少, 多样性降低, 亚硝化单胞菌属成为优势种群, 占比达11.5%。提高曝气量至120 L/h并在此条件下运行7 d后, 亚硝态氮积累率下降至82%;维持C/N在3.5~7.6之间, 系统中NH₄+-N的去除率均能稳定在95%左右, NO₂--N积累率也均可达93%以上;过度曝气会破坏短程硝化系统, 过度曝气至第8天, 亚硝态氮的积累率降至48.89%。      

Effect of Cd(II) on Different Bacterial Species Present in a Single Sludge Activated Sludge Process for Carbon and Nutrient Removal

Heavy metal cadmium(II) was added stepwise into an A2O pilot plant to investigate the toxic effects of Cd(II) on the removal efficiencies, kinetic parameters (yield coefficients and maximum specific growth rates) and reaction rates of carbon, nitrogen and phosphate for the acclimatized heterotrophic and autotrophic bacteria. Results showed that 2?mg/L Cd(II) initially affected the biological reaction of phosphate removal. At Cd(II) 5?mg/L, the efficiencies of total nitrogen removal and nitrification were substantially dropped. At the same time, the yield coefficient and maximum specific growth rate of heterotrophs were significantly decreased from 0.8?g?COD/g?COD and 6.44?day?1 to 0.54?g?COD/g?COD and 4.67?day?1, respectively. And, the denitrification rate was inhibited by about 61%. The inhibition percentages of anaerobic release, anoxic and aerobic uptake rates of phosphate were about 76, 64, and 90%, respectively. When Cd(II) concentration was continually increased up to 35?mg/L, removal efficiency of chemical oxygen demand (COD) was significantly dropped. However, there was no obvious inhibition on the biological reactions of anaerobic ammonification.     

Comparison of Two Model Concepts for Simulation of Nitrogen Removal at a Full-Scale Biological Nutrient Removal Pilot Plant

The experimental studies conducted at the Hanover-Gümmerwald pilot wastewater treatment plant (WWTP) focused on minimizing nitrogen loads discharged during stormwater events. The data collected during the plant operation were used for a long-term process simulation. The aim of this study was to compare predictive capabilities of two different mechanistic models (ASM2d and ASM3P) in terms of nitrogen removal. The influent wastewater composition was generated using on-line measurements of only three parameters (COD, N–NH4+, P–PO43?) and the model predictions were primarily compared with on-line data (concentrations of N–NH4+, N–NO3?) originating from the aerobic zone of the bioreactor. The simulation results confirmed the experimental data concerning the capabilities of the system for handling increased flows during stormwater events. The predicted peaks of N–NH4+ at the line with the quadruple dry weather flow rate were normally exceeding 8?g?N?m?3 (similar to the observations), whereas no (or minor) peaks of N–NH4+ were predicted for the line with the double dry weather flow rate. The relationships between ASM2d and ASM3P predictions for N–NH4+ and N–NO3? were highly correlated (r2 = 0.83–0.99) with the slopes remaining close to 1.0. Both models appear to be equally suitable for practical applications in common municipal WWTPs.     

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%.