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.     

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.     

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.     

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.     

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.     

Strategy for Complete Nitrogen Removal in Bioreactor Landfills

Waste acclimation and batch microcosm studies containing digested municipal solid waste were conducted at different temperatures (22, 35, and 45°C) and gas-phase oxygen concentrations (0.7–100%, by volume) to provide guidance for field-scale implementation of in situ nitrogen removal processes. Results demonstrate that in situ ammonia–nitrogen is feasible in decomposed aerated solid waste environments at the gas-phase oxygen concentrations and temperatures evaluated and the potential for simultaneous nitrification and denitrification in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. Small amounts of oxygen were found sufficient for nitrification/ammonia removal to proceed, although removal rates increase with oxygen concentration. Laboratory results suggest field-scale implementation of in situ nitrogen removal occur in small dedicated treatment zones containing previously degraded waste (later in the life of a bioreactor landfill). Model simulations indicate removal of ammonia–nitrogen to low levels can occur with relatively short aeration depths (depth estimates ranged from 1.6 to 7.2?m below the point of leachate injection). Field-scale verification of these depth estimates is required prior to routine acceptance.     

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.     

Contrasting the Benefits of Primary Clarification versus Prefermentation in Activated Sludge Biological Nutrient Removal Systems

The potential benefits prefermentation can provide to biological nutrient removal are measured and compared to the costs of excess oxygen consumption and sludge production incurred by an activated sludge system that utilizes prefermentation, instead of primary clarification. Prefermentation was found to produce superior performance in regards to enhanced biological phosphorus removal. A lower soluble orthophosphorus effluent value [3.2?mg/L for the prefermented activated sludge (PAS) train versus 4.6?mg/L for the control train with primary clarification (PCAS)] and a higher percent phosphorus (% P) content of the biomass (9.0% for the PAS train versus 7.8% for the PCAS train) were both found to be statistically significant (P values of 4.26×10?5 and 0.0082, respectively). In addition statistically significant improvements in denitrification rates and reduced observed yields were observed due to prefermentation. However statistically significant increases in solids inventory and in particular oxygen uptake rates offset these improvements. Waste activated sludge production was slightly higher in the PAS train but was not found to be statistically significant.     

Nitrogen Removal in Recirculating Sand Filter Systems with Upflow Anaerobic Components

Septic systems can present a risk to human health by releasing highly soluble nitrate–nitrogen into the groundwater. A research and demonstration study undertaken in Black River Falls, Wisconsin, evaluated several promising biofilter technologies for on-site nitrogen removal. Duplicate recirculating sand filter-upflow anaerobic systems with a design hydraulic loading rate of 954?L/day (250?gal/day) were used to treat septic tank effluent from a correctional institution and produced a treated wastewater with a total nitrogen concentration of 15.2?mg/L for System 1 and 18.2?mg/L for System 2, or 72.0 and 63.0% nitrogen removal, respectively. The differences between the two systems appear to have been the result of process configuration changes made over the duration of the study. This paper evaluates the nitrogen removal performance of the recirculating sand filter-upflow anaerobic systems and the effect of operational and environmental factors, including the recirculation ratio, BOD5/NO3?, and temperature. Nitrogen removal was limited by the recirculation ratio with the maximum total nitrogen removal of 70.1% when the recirculation ratio = 3. Improved performance was also noted for temperatures ≥ 20°C and BOD5/NO3? ≥ 8. Low temperatures adversely affected nitrification and low BOD5/NO3? adversely affected denitrification. The relationships among nitrogen removal, recirculation ratio, BOD5/NO3?, and temperature are also discussed.     

Simultaneous Removal of Organic Matter and Nitrogen Compounds in Autoaerated Biofilms

This paper describes the simultaneous removal of organic matter and nitrogen compounds carried out using an autoaerated multispecies biofilm growing on gas-permeable hollow-fiber membranes. In order to perform the aerobic heterotrophic oxidation and nitrification processes, the biofilm absorbs atmospheric oxygen through the inside walls of hollow fibers and consumes substrate from the bulk liquid. A mass balance calculated the consumed oxygen. Depending on the removed organic and nitrification rates, the oxygen flux through the hollow fibers can reach up to 90% of the total oxygen consumed, whereas the remaining 10% pertains to the dissolved oxygen from the influent wastewater. Without the biofilm the oxygen transfer rate through clean hollow fibers is 3.5?g?m?2?day?1, whereas the oxygen transfer rate through the biomembrane (hollow fiber+biofilm) achieves a maximum value of 25?g?m?2?day?1. The enhanced oxygen transfer using the biological pathway may be attributed, among many other factors, to the mobility of the microorganisms generating microturbulence, which produces more active bioturbulent diffusiveness than the molecular diffusion in the biofilm. It has also shown that the oxygen utilization efficiency was affected by the substrate utilization rate.     

Performance of a Biofilm Airlift Suspension Reactor for Synthetic Wastewater Treatment

Performance stability of a biofilm airlift suspension reactor (BASR) was studied using ethanol as a substrate. The main objective of this research was to investigate the applicability of the reactor as a wastewater treatment process by examining the effects of soluble chemical oxygen demand (SCOD) loading rate and hydraulic retention time (HRT) on the performance of the reactor. SCOD removal of 90% or higher was achieved at an HRT of 45 min with loading rates from 10 to 18 kg SCOD/m3?day. Similar results were obtained at HRTs of 60 and 90 min and a SCOD loading rate of 10 kg SCOD/m3?day. Nitrification occurred in the system when the ratio of SCOD to ammonia nitrogen was changed from 10:1 to 6:1. The morphology of the biofilm in the BASR was denser and thicker when nitrifiers grew in the biofilm. Filamentous overgrowth was observed from time to time and proper chlorine dose successfully suppressed its growth. The oxygen uptake rate was an effective tool for monitoring the effect of chlorination.     

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.     

Nitrogen Transformations during Soil–Aquifer Treatment of Wastewater Effluent—Oxygen Effects in Field Studies

Depth-dependent oxygen concentrations and aqueous-phase total ammonia and nitrate/nitrite ion concentrations were measured in the field during the infiltration of wastewater effluent. Measurements illustrated the dependence of nitrogen fate and transport on oxygen availability. Infiltration basins were operated by alternating wet (infiltration) and dry periods. During infiltration periods, ammonia was removed within the top few feet of sediments via adsorption. Biochemical activity rapidly eliminated residual molecular oxygen in the infiltrate, making the soil profile anoxic. During dry periods, oxygen reentered the basin profile and sorbed ammonia was converted to nitrate via nitrification. Oxygen penetrated to a depth of about 0.6?m?(2?ft) within the first few days of dry periods. At greater depths, oxygen levels increased more slowly due to a combination of slow transport kinetics and biochemical (nitrogenous) oxygen demand. During normal wet/dry basin cycles consisting of about 4 wet and 4 dry days, the local vadose zone remained anoxic at depths greater than about 1.5?m?(5?ft) below land surface. As a consequence, conditions for denitrification were satisfied in the deeper sediments. That is, the nitrate nitrogen produced in near surface sediments moved freely downward with infiltrating water where it encountered an extensive anoxic zone before reaching local monitoring or extraction wells. The relative importance of dissolved organics and sorbed ammonia as electron donors for denitrification reactions remains to be established.     

Effect of Substrate Nitrogen/Chemical Oxygen Demand Ratio on the Formation of Aerobic Granules

The effect of the substrate nitrogen/chemical oxygen demand (N/COD) (mg/mg) ratio on the formation and characteristics of aerobic granules for simultaneous organic removal and nitrification were studied in four sequencing batch reactors operated at different substrate N/COD ratios ranging from 5/100 to 30/100. Results showed that aerobic granules formed at the substrate N/COD ratios studied, and both nitrifying and heterotrophic activities of aerobic granules were governed by the substrate N/COD ratio. The nitrifying activity was significantly enhanced with the increase of the substrate N/COD ratio, while the heterotrophic activity decreased. By determining elemental compositions of aerobic granules cultivated at different substrate N/COD ratios, it was revealed that the cell hydrophobicity was inversely related to the ratio of cell oxygen content to cell carbon content of aerobic granule. The production of extracellular polysaccharides showed a decreasing trend as the substrate N/COD ratio increased. This is probably due to enriched nitrifying population with the high N/COD ratios. This study clearly demonstrated that an aerobic granule-based sequencing batch reactor would have a great potential for simultaneous organic oxidation and nitrification.     

Influence of COD/N Ratios on Simultaneous Removal of C and N Compounds in Biological Wastewater Treatment in Sequencing Fed-Batch Reactor and Kinetic Analysis

The impact of chemical oxygen demand/nitrogen (COD/N) values of feed wastewater on COD and nitrogen removal and biomass growth in a sequencing fed-batch reactor (SFBR) operation was investigated. The multiple microbial reactions involved in the simultaneous removal process of carbonaceous and nitrogenous components in the SFBR system were analyzed using a set of kinetics mathematical model. The results indicate that COD/N ratios strongly influence COD and total nitrogen removal efficiency. The COD removal efficiency per gram microorganism changed from 64.3 to 78.1% at COD/N = 11.9–2.5. The total nitrogen removal efficiency changed from 10.3 to 34.2% at COD/N = 2.5–11.9. However, variable COD/N ratios of feed wastewater are not marked for biomass growth rate.     

Simultaneous Nitrogen and Phosphorus Removal in a Continuously Fed and Aerated Membrane Bioreactor

This research demonstrated the feasibility of simultaneous biological nitrogen and phosphorous removal in a single tank membrane bioreactor without cycling of air and/or feed through operation at a low dissolved oxygen (DO) and a high biomass concentration. Chemical oxygen demand removal efficiency was more than 98% and total nitrogen removal efficiency was 55%. Seventy-five percent of the total nitrogen removal was through simultaneous nitrification–denitrification (SND) and 25% through assimilation into the biomass. Interestingly, more than 98% phosphorous was removed and microbiological analysis showed the presence of polyphosphate-accumulating organisms in the activated sludge. The operating mixed-liquor suspended solids was between 16 and 23?g/L. The optimum DO was found to be 0.7–0.8?mg/L.     

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.     

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.     

Simultaneous Wastewater Nutrient Removal by a Novel Hybrid Bioprocess

A combined activated sludge–biofilm bioprocess called TNCU-I was developed by adding a rotating biological contactor to the aerobic zone of a traditional A2O process in order to solve the sludge retention time conflict between nitrifiers and phosphate accumulating organisms (PAOs), and the carbon source competition between denitrifiers and PAO. The TNCU-I process shows excellent carbon, nitrogen, and phosphate removal performance when treating synthetic wastewater. The process also achieved a more stable nitrification performance than the A2O process. The specific nitrification rate, the specific anoxic and aerobic phosphate uptake rates, the specific denitrification rate, and the specific anaerobic phosphate release rate were determined by a series of batch experiments. Such data were further analyzed to optimize the volume ratio of the TNCU-I anaerobic, anoxic, and aerobic tanks. The optimized process was also operated to confirm the performance. In addition, both Nitrosospira and Nitrospira were identified in the activated sludge and the rotating biological contactor biofilm by 16S rDNA based biotechnology.     

Oxidation-Reduction Potential as a Monitoring Tool in a Low Dissolved Oxygen Wastewater Treatment Process

Research was undertaken to investigate the relationship between two biochemical events and the oxidation-reduction potential (ORP) measurement in a low dissolved oxygen (D.O.) wastewater treatment process. The biological events considered were the depletion of organic waste and the depletion of ammonia nitrogen. Two lab-scale sequencing batch reactors fed with a synthetic waste were operated under controlled conditions using seed material from a local wastewater treatment plant. The on-line monitoring of ORP, D.O., and pH was complemented by intensive track studies in which physical measurements of biochemical parameters such as chemical oxygen demand and TN were taken. The results indicated that low D.O. processes (e.g., the simultaneous nitrification/denitrification process) may have their own distinctive on-line profiles, with certain biochemical events such as the depletion of organic carbon and the depletion of ammonia nitrogen being readily detectable on the ORP profile. The fact that these specific events are displayed on the on-line ORP profile means that the profile could possibly be used as a process control parameter.