Effluent Total Nitrogen Concentration Research Articles

Evaluation of High Density Algal Cultivation for Secondary Wastewater Polishing.

This study evaluated the performance of an algal membrane bioreactor (A-MBR) for secondary wastewater effluent polishing and determined the membrane fouling behavior and dominance of algae in the A-MBR. The continuous flow A-MBR (effective volume = 7.2 L) was operated with low biomass wastage for more than 180 days, resulting in an average algal mixed liquor suspended solid concentration of 4922 mg/L. At the influent concentrations of 43 mg/L COD, 1.6 mg/L total phosphorus (TP), and 11.8 mg/L total nitrogen (TN), the effluent COD, TP and TN concentrations were 26 ± 6 mg/L, 0.7 ± 0.3 mg/L, and 9.6 ± 1.2 mg/L, respectively. High-density algae cultivation facilitated P adsorption and chemical precipitation. However, the TN removal efficiency was only 14% because of low biomass wastage. Although bacteria represented less than 2% of the total biomass in the A-MBR, bacterial growth in the secondary wastewater effluent accelerated membrane fouling.

Bioremediation of Oil Containing Seawater by Membrane-Aerated Biofilm Reactor

A lab-scale membrane-aerated biofilm reactor (MABR), inoculated with ADB350 M (the engineering bacteria on degrading petroleum hydrocarbon), was developed to process the oil-spilled seawater pretreated by rhamnolipid. Effects of the rhamnolipid/oil ratios, nitrogen and phosphorus additions, aeration pressures, and setup rotation velocities on the MABR performance were investigated. Results showed that under the optimal conditions, effluent concentrations of chemical oxygen demand (COD), oil content, total phosphorus (TP), and total nitrogen (TN) were 39 mg/L, 2.3 mg/L, 0.29 mg/L, and 1.9 mg/L, respectively. Throughout the treatment, the ADB350 M exerted good adherence to the aerated membranes. In comparison with the direct-spread of engineering bacteria, the membrane-immobilization method reduced losses of the inoculums inside the seawater. Supplement of rhamnolipid was conducive to the improvement of the biofilm hydrophobicity by changing the polysaccharide/protein ratios of extracelluar polymeric substa...

Simultaneous biological removal of nitrogen and phosphorus in a vertical bioreactor

Nutrients pollution has become a global environmental threat. A large fraction of nutrient pollution is caused by point sources like the discharges of untreated domestic and industrial wastewater. As a result, there is a great demand to develop reliable, compact and efficient nutrient removal technologies. In the wastewater industry, most of the bioreactors have a large foot print with a plane configuration. Furthermore, the existing nutrient removal processes are based on well-known microbial species of genus Nitrosomonas and Nitrobacter involved in nitrification/denitrification and Candidatus Accumulibater Phosphatis responsible for biological phosphorous removal (BPR). The present work is unprecedented in two aspects: (1) The biological nitrogen and phosphorus removal from wastewater occurred in a multistage vertical, tubular bioreactor and (2) Two abundant microbial species were responsible for the simultaneous nitrification–denitrification–BPR in this vertical bioreactor. The abundant microbial populations included an unidentified bacteria of Saprospiraceae family and bacteria affiliated with the genus Zoogloea. The composition of the synthetic wastewater used in this study was: total phosphorous (TP) 32.6±0.7mg/L, total nitrogen (TN) 272±7.5 in which 45±1.8mg/L was ammonia-nitrogen (NH3-N). The bioreactor was continuously operated for over 350 days at constant flowrate, temperature and pH of 240 (L/day), 22–24 (°C) and 7–7.5. The results showed that simultaneous nitrification–denitrification–BPR was the dominant process by an, as yet not fully classified, microbial species. The effluent TP and TN concentrations were 2.7±0.4 and 4.3±1.2mg/L respectively. Concentrations of NH3-N, NO2− and NO3-N in the effluent were 0.7±0.1, 0.8±0.5 and 0.3±0.1. The simultaneous nitrification–denitrification–BPR was highly effective delivering above 90% TN and TP removal efficiency. The successful results presented in this paper have led to the construction of a 20,000L/day demonstration plant in the City of Pickering, Ontario.

Suppressing Nitrite-oxidizing Bacteria Growth to Achieve Nitrogen Removal from Domestic Wastewater via Anammox Using Intermittent Aeration with Low Dissolved Oxygen.

Achieving nitrogen removal from domestic wastewater using anaerobic ammonium oxidation (anammox) has the potential to make wastewater treatment energy-neutral or even energy-positive. The challenge is to suppress the growth of nitrite-oxidizing bacteria (NOB). This study presents a promising method based on intermittent aeration with low dissolved oxygen to limit NOB growth, thereby providing an advantage to anammox bacteria to form a partnership with the ammonium-oxidizing bacteria (AOB). The results showed that NOB was successfully suppressed using that method, with the relative abundance of NOB maintained between 2.0–2.6%, based on Fluorescent in-situ Hybridization. Nitrogen could be effectively removed from domestic wastewater with anammox at a temperature above 20 °C, with an effluent total nitrogen (TN) concentration of 6.6 ± 2.7 mg/L, while the influent TN and soluble chemical oxygen demand were 62.6 ± 3.1 mg/L and 88.0 ± 8.1 mg/L, respectively.

Nitrogen Removal Controlled by an Ammonium-Analyser at the north Pest Wastewater Treatment Plant

Abstract At the North Pest Wastewater Treatment Plant, a nutrient removal process has been in operation since 2011. New tanks have been built, which can receive approximately half of the pre-settled wastewater. A predenitrification system has been planned and built both to the old and new lines. Due to the relatively small anoxic zones, periodic aeration was initiated first in the new line to achieve the lowest possible effluent total nitrogen concentration. Because of its positive impact, the operation of periodic aeration was initiated in the old line as well. Ammonium-analysers are used to control the aeration periods. Due to this process, the plant can provide a very low total nitrogen effluent value (below 10 mg dm-3 on average) as well as save energy and operational costs.

Achieving low effluent NO3-N and TN concentrations in low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio without using external carbon source

Two mathematical models were used to optimize the performance of a full-scale biological nutrient removal (BNR) activated treatment plant, a plug-flow bioreactors operated in a 3-stage phoredox process configuration, anaerobic anoxic oxic (A2/O). The ASM2d implemented on the platform of WEST2011 software and the BioWin activated sludge/anaerobic digestion (AS/AD) models were used in this study with the aim of consistently achieving the designed effluent criteria at a low operational cost. Four ASM2d parameters (the reduction factor for denitrification \((\eta _{NO_3 H} )\), the maximum growth rate of heterotrophs (µH), the rate constant for stored polyphosphates in PAOs (qpp), and the hydrolysis rate constant (kh)) were adjusted. Whereas three BioWin parameters (aerobic decay rate (bH), heterotrophic dissolved oxygen (DO) half saturation (KOA), and YP/acetic) were adjusted. Calibration of the two models was successful; both models have average relative deviations (ARD) less than 10% for all the output variables. Low effluent concentrations of nitrate nitrogen (N-NO3), total nitrogen (TN), and total phosphorus (TP) were achieved in a full-scale BNR treatment plant having low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio (COD/TKN). The effluent total nitrogen and nitrate nitrogen concentrations were improved by 50% and energy consumption was reduced by approximately 25%, which was accomplished by converting the two-pass aerobic compartment of the plug-flow bioreactor to anoxic reactors and being operated in an alternating mode. Findings in this work are helpful in improving the operation of wastewater treatment plant while eliminating the cost of external carbon source and reducing energy consumption.

Carbon Footprint Analyses of Mainstream Wastewater Treatment Technologies under Different Sludge Treatment Scenarios in China

With rapid urbanization and infrastructure investment, wastewater treatment plants (WWTPs) in Chinese cities are putting increased pressure on energy consumption and exacerbating greenhouse gas (GHG) emissions. A carbon footprint is provided as a tool to quantify the life cycle GHG emissions and identify opportunities to reduce climate change impacts. This study examined three mainstream wastewater treatment technologies: Anaerobic–Anoxic–Oxic (A–A–O), Sequencing Batch Reactor (SBR) and Oxygen Ditch, considering four different sludge treatment alternatives for small-to-medium-sized WWTPs. Following the life cycle approach, process design data and emission factors were used by the model to calculate the carbon footprint. Results found that direct emissions of CO2 and N2O, and indirect emissions of electricity use, are significant contributors to the carbon footprint. Although sludge anaerobic digestion and biogas recovery could significantly contribute to emission reduction, it was less beneficial for Oxygen Ditch than the other two treatment technologies due to its low sludge production. The influence of choosing “high risk” or “low risk” N2O emission factors on the carbon footprint was also investigated in this study. Oxygen Ditch was assessed as “low risk” of N2O emissions while SBR was “high risk”. The carbon footprint of A–A–O with sludge anaerobic digestion and energy recovery was more resilient to changes of N2O emission factors and control of N2O emissions, though process design parameters (i.e., effluent total nitrogen (TN) concentration, mixed-liquor recycle (MLR) rates and solids retention time (SRT)) and operation conditions (i.e., nitrite concentration) are critical for reducing carbon footprint of SBR. Analyses of carbon footprints suggested that aerobic treatment of sludge not only favors the generation of large amounts of CO2, but also the emissions of N2O, so the rationale of reducing aerobic treatment and maximizing anaerobic treatment applies to both wastewater and sludge treatment for reducing the carbon footprint, i.e., the annamox process for wastewater nutrient removal and the anaerobic digestion for sludge treatment.

Mixed sulfur-iron particles packed reactor for simultaneous advanced removal of nitrogen and phosphorus from secondary effluent.

A mixed sulfur-iron particles packed reactor (SFe reactor) was developed to simultaneously remove total nitrogen (TN) and total phosphorus (TP) of the secondary effluent from municipal wastewater treatment plants. Low effluent TN (<1.5mg/L) and TP (<0.3mg/L) concentrations were simultaneously obtained, and high TN removal rate [1.03gN/(L·d)] and TP removal rate [0.29g P/(L·d)] were achieved at the hydraulic retention time (HRT) of 0.13h. Kinetic models describing denitrification were experimentally obtained, which predicted a higher denitrification rate [1.98gN/(L·d)] of SFe reactor than that [1.58gN/(L·d)] of sulfur alone packed reactor due to the mutual enhancement between sulfur-based autotrophic denitrification and iron-based chemical denitrification. A high TP removal obtained in SFe reactor was attributed to chemical precipitation of iron particles. Microbial community analysis based on 16S rRNA revealed that autotrophic denitrifying bacteria Thiobacillus and Sulfuricella were the dominant genus, indicating that autotrophic denitrification played important role in nitrate removal. These results indicate that sulfur and iron particles can be packed together in a single reactor to effectively remove nitrate and phosphorus.

Multi-objective optimisation of wastewater treatment plant control to reduce greenhouse gas emissions

This study investigates the potential of control strategy optimisation for the reduction of operational greenhouse gas emissions from wastewater treatment in a cost-effective manner, and demonstrates that significant improvements can be realised. A multi-objective evolutionary algorithm, NSGA-II, is used to derive sets of Pareto optimal operational and control parameter values for an activated sludge wastewater treatment plant, with objectives including minimisation of greenhouse gas emissions, operational costs and effluent pollutant concentrations, subject to legislative compliance. Different problem formulations are explored, to identify the most effective approach to emissions reduction, and the sets of optimal solutions enable identification of trade-offs between conflicting objectives. It is found that multi-objective optimisation can facilitate a significant reduction in greenhouse gas emissions without the need for plant redesign or modification of the control strategy layout, but there are trade-offs to consider: most importantly, if operational costs are not to be increased, reduction of greenhouse gas emissions is likely to incur an increase in effluent ammonia and total nitrogen concentrations. Design of control strategies for a high effluent quality and low costs alone is likely to result in an inadvertent increase in greenhouse gas emissions, so it is of key importance that effects on emissions are considered in control strategy development and optimisation.

Simultaneous COD and Nitrogen Removal in Up-Flow Microaerobic-Oxic (M/O) Process for Domestic Wastewater Treatment

A novel process for improving the energy use and treatment efficiency of the biological nitrogen removal process, up-flow microaerobic-oxic (M/O) process which is composed of up-flow micro-aerobic and aeration was proposed based on a laboratory scale for domestic wastewater treatment, the dissolved oxygen (DO) in up-flow micro-aerobic was in the range of (0~0.5) mg/L. The M/O process performance under different hydraulic retention time (HRT) and Internal return ratio (r) was investigated. Under the optimal conditions, the average removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN) and ammonium nitrogen (NH4+-N) were 89.1%, 64.1%, and 96.6 % with effluent concentrations of COD, TN and NH4+-N less than 50,15 and 8mg/L, respectively. The distribution of sludge particles diameter and microbial activity of activated sludge were also measured, the mean particle diameter was in the range of 180~250μm and the SOURT was 13.11 mgO2/(gMLVSSh). Up-flow micro-aerobic (M/O) reactor has the advantages of more stable performance and better resistance to the load shock than the conventional A/O process within continuous running period of 130 days.

Uptake by Algae of Dissolved Organic Nitrogen from BNR Treatment Plant Effluents

The importance of dissolved organic nitrogen (DON) in wastewater treatment effluent has dramatically increased as permitted effluent total nitrogen (TN) concentrations have been decreased to very low levels in response to problems with impaired surface water quality from eutrophication. For conventional secondary treatment, DON typically accounts for less than 10% of the effluent TN, but it is a major component (>50%) in effluents from advanced biological nutrient removal (BNR) treatment plants, for which most of the inorganic nitrogen species and effluent suspended solids are removed. DON persists in effluents from BNR systems and little is known about the potential impact of the effluent DON from these facilities on surface water quality. Of particular interest is what portion of DON is readily available for algae consumption or can be converted to forms to support algal growth, and what type of substances compose DON. To develop a better understanding of the occurrence and bioavailability of DON in effluents from advanced BNR systems, a new protocol was developed for measuring the readily bioavailable DON and forms of DON that are not readily taken up by algae (recalcitrant DON). An anion exchange resin was used to remove nitrate while an XAD-8 resin was used to remove hydrophobic forms of DON. To assess the bioavailability of wastewater-derived DON, algal growth assays were performed in the presence of bacteria in effluents from ten municipal BNR wastewater treatment plants. The results showed only minor difference in the algal growth and DON consumption between the untreated and XAD-8 treated samples. Growth of algae and DON consumption were not observed in the eluent from XAD-8 resins, despite the fact that this fraction contained up to approximately 30% of the DON. These findings indicate that the hydrophobic DON retained on the XAD-8 resin is not bioavailable to algae over periods of several weeks and that the XAD-8 treatment combined with an anion exchange resin can be used to quantify and separate this recalcitrant form of DON from bioavailable DON and nitrate. This title belongs to WERF Research Report Series . ISBN: 9781780401386 (eBook)

Field-scale application of spent sulfidic caustic as a source of alternative electron donor for autotrophic denitrification

Biological reuse of spent sulfidic caustic (SSC) originating from oil refineries is a promising method for the petrochemical industry because of low handling cost. SSC typically contains high concentrations of sulfur, with the most dominant sulfur compounds being sulfide (S(2-)). SSC is also characterized by a high pH and elevated alkalinity up to 5-15% by weight. Because of these characteristics, SSC can be used for denitrification of NO3(-)-N in the biological nitrogen removal process as both the electron donor and buffering agent in sulfur-utilizing autotrophic denitrification. In this study, two kinds of SSC (SSC I, SSC II) produced from two petrochemical companies were used for autotrophic denitrification in a field-scale wastewater treatment plant (WWTP). The effluent total nitrogen (TN) concentration in this process was about 10.5 mg/L without any external carbon sources and the nitrification efficiency was low, about 93.0%, because of alkalinity deficiency in the influent. The injection of SSC I, but not SSC II, promoted nitrification efficiency, which was attributed to the difference in the NaOH/S ratio between SSC I and II. SSC was injected based on sulfide concentration of SSC required to denitrify NO3(-)-N in the WWTP. SSC I had higher NaOH/S than SSC II and thus could supply more alkalinity for nitrification than SSC II. On the other hand, additional TN removal of about 9.0% was achieved with the injection of both SSCs. However, denitrification efficiency was not proportionally increased with increasing SSC injection because of NO3(-)-N deficiency in the anoxic tank due to the limited capacity of the recycling pump. For the same reason, sulfate concentration, which is the end product of sulfur-utilizing autotrophic denitrificaiton in the effluent, was also not increased with increasing SSC injection.

Hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater using membrane diffusion packed-bed bioreactor

A lab-scale membrane diffusion packed-bed bioreactor was used to investigate hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater. After start-up, the bioreactor had been operated for 165 days by stepwise increasing influent loading rates at 30 and 15°C. The results indicated that this bioreactor could achieve relatively high nitrogen removal efficiencies. The denitrification rates reached 0.250 and 0.230 kg N/(m(3)d) at 30 and 15°C respectively. The total nitrogen concentration in effluent was entirely below 2.0 mg/L at the steady operation state. The average increase of total organic carbon in effluent was approximately 0.41 mg/L, suggesting the risk of organic residue can be completely controlled. Dissolved oxygen (DO) did not show obviously negative effects on hydrogenotrophic denitrification. There was only slight decrease of DO concentration in effluent, which demonstrated almost all of the hydrogen was used for nitrate reduction.

Influence of temperature and pH on nitrogen removal in a series of maturation ponds treating anaerobic effluent

This paper presents an evaluation of the influence of pH and temperature on nitrogen removal in a series of three shallow maturation ponds serving as post-treatment of upflow anaerobic sludge blanket (UASB) reactor effluent (approximately 200 population equivalent). Monitoring was from January 2007 to May 2009. Throughout this period, the ponds maintained relatively stable operational conditions in terms of depth and hydraulic retention time, thus enabling the evaluation of the influence of variations in temperature and pH on the performance in terms of nitrogen removal. In general, as expected, the removal of nitrogen was more effective when the temperature and pH of the ponds were higher, implying that these variables are relevant in the removal of nitrogen. Due to the fact that these parameters are included in the prediction equations for effluent ammonia and total nitrogen found in traditional models from the literature, fitting of the models to the experimental data was investigated. The models gave acceptable fittings in the estimation of effluent concentrations of ammonia and total nitrogen from maturation ponds treating UASB reactor effluent.

Fate and toxicity of melamine in activated sludge treatment systems after a long-term sludge adaptation

Melamine is a nitrogen-rich (67% nitrogen by mass) heterocyclic aromatic compound that could significantly increase effluent total nitrogen concentrations. In this study, we investigated the degradation of melamine and its impact on activated sludge operations by employing two common activated sludge processes, namely the Modified Ludzack-Ettinger (MLE) process and the continuous stirred tank reactor (CSTR) process. Melamine was dosed continuously from day 125 in both activated sludge treatment systems at an influent concentration of 3 mg/L for about 100 days. Even after such a long period of sludge adaptation, melamine appeared not to be easily biodegradable. The average melamine removal efficiencies in the CSTR and MLE systems were 14 ± 10% and 20 ± 15%, respectively. There was no significant difference in melamine removal between the two different activated sludge processes. The long-term input of melamine resulted in a decrease in the nitrifying bacterial activities (by 82 ± 8%) and population in both systems. Short-term microtiter assay results also showed that melamine reduced activated sludge growth by 80% when supplied at a concentration of 75.6 mg/L. These results suggest that sludge adaptation plays a minimal role in melamine degradation, as the enzymes responsible for hydrolytic deamination of melamine in activated sludge are not easily induced. The insignificant biodegradation of melamine is also attributed to bacterial growth inhibition under long-term dosing conditions with melamine, resulting in a significant decrease in effluent water quality.

Seasonal Performance of Sequencing Batch Biofilm Reactors and Ecosystem Sewage Treatment Hybrid Processes in Small Towns of the Three Gorges Reservoir Area in China

ABSTRACTThis study aimed to address the problems of small towns, e.g. low economy, undeveloped technology and management level, and fluctuant water quality and water quantity. To develop an efficient low-cost small-town sewage treatment technology, the integration of sequencing batch type bioreactor/ecosystem hybrid treatment process was chosen. In this experiment, the bioreactor unit of the process included a sequencing batch biofilm reactor (SBBR), while the ecosystem unit applied a sequencing constructed wetland (SCW) based on a polyurethane foam filler in a matrix. By changing the operation model, tests were carried out to find the key parameters of the optimal operation model for the sequencing batch type bioreactor/ecosystem hybrid treatment process in different seasons. The experiment was conducted throughout a year of operation after setup. The results showed that when the bio- and ecosystem reactors ran together in combination at a temperature of 15 °C ∼ 25 °C in spring and autumn, The final effluent chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), and total nitrogen (TN) concentrations of the hybrid reactors were 48 mg/L, 7 mg/L, and 16 mg/L, respectively, with a corresponding total removal efficiencies of 86%, 89%, and 79%. When the ecosystem reactors ran independently in the temperature range of 25 °C ∼ 35 °C in the summer, the effluent COD, NH4+-N, and TN concentrations were 47 mg/L, 7.3 mg/L, and 17.3 mg/L respectively, with a corresponding total removal rate of 84%, 87%, and 74%. The bioreactors and ecosystem reactors ran together in combination at 5 °C ∼ 15 °C in the winter and the final COD, NH4+-N, and TN concentrations of the hybrid reactors effluent were, respectively, 54 mg/L, 11 mg/L, and 18 mg/L, with a corresponding total removal of 86%, 84%, and 76%. The research developed an integration of sequencing batch type bioreactor/ecosystem hybrid treatment process with important realistic significance and practical value. The designed operation models are able to be used in guiding practical engineering.

Performance of an ANAMMOX reactor treating wastewater generated by antibiotic and starch production processes

A pilot-scale anaerobic ammonia oxidation (ANAMMOX) reactor was used to treat mixed wastewater resulting from a chlortetracycline and starch production process. The results, collected over the course of 272 days, show that the ratio of influent ammonium to nitrite, pH, and temperature can all affect the efficiency of nitrogen removal. The ratio of influent ammonium to nitrite was maintained at about 1:1 at a concentration below 200 mg·L−1 for both influent ammonium and nitrite. The total nitrogen (TN) loading rate was 0.15–0.30 kgN·m−3·d−1, pH remained at 7.8–8.5, and temperature was recorded at 33±1°C. The rate of removal of ammonia, nitrite, and TN were over 90%, 90%, and 80%, and the effluent ammonium, nitrite and TN concentrations were below 50, 30, and 100 mg·L−1.

Comparative studies on the differently operated trains of the North-Budapest Wastewater Treatment Plant

In order to reduce the pollution load of the Danube, the North-Budapest Wastewater Treatment Plant has been upgraded to enhanced nitrogen removal by establishing a new activated sludge treatment line and modifying the existing unit for nitrification and denitrification. As both the influent flow rate and the influent chemical oxygen demand (COD), biological oxygen demand (BOD(5)) and total suspended solids (TSS) concentration levels remained far below the design values, setting one fourth of the reactor volume out of operation in the Old Line, and operating the nitrification reactor of the New Line with part-time aeration proved to be possible. Analytical data as well as simulation studies supported the advantage of the intermittent-aeration process in efficient N-removal. However, the lengths of the aerated periods have to be increased with decreasing temperature, and thereby effluent total nitrogen (TN) concentration can increase due to decreasing denitrification efficiency. Potential occurrence of low-dissolved oxygen (DO) bulking should be hindered through applying an efficient anoxic selector system.

WEF/WERF study of BNR plants achieving very low N and P limits: evaluation of technology performance and process reliability

The Water Environment Research Foundation (WERF) funded a two-year comprehensive study of nutrient removal plants designed and operated to meet very low effluent total nitrogen (TN) and total phosphorus (TP) concentrations. WERF worked with the Water Environment Federation (WEF) to solicit participation of volunteers and provide a forum for information exchange at workshops at its annual conferences. Both existing and new technologies are being adapted to meet requirements that are as low as 3.0 mg/L TN and 0.1 mg/L TP, and there is a need to define their capabilities and reliabilities in the real world situation of wastewater treatment plants. A concern over very low daily permits for ammonia caused the work to be extended to include nitrification reliability. This effort focused on maximizing what can be learned from existing technologies in order to provide a database that will inform key decision makers about proper choices for both technologies and rationale bases for statistical permit writing. To this end, managers of 22 plants, 10 achieving low effluent TP, nine achieving low effluent TN, and three achieving low effluent NH(3)-N, provided three years of operational data that were analyzed using a consistent statistical approach. Technology Performance Statistics (TPSs) were developed as three separate values representing the ideal, median, and reliably achievable performance. Technological conclusions can be drawn from the study in terms of what can be learned by comparing the different nutrient removal and nitrification processes employed at these 22 plants.

Full-scale operating experience of deep bed denitrification filter achieving &amp;lt;3 mg/l total nitrogen and &amp;lt;0.18 mg/l total phosphorus

The Arlington County Wastewater Pollution Control Plant (ACWPCP) is located in the southern part of Arlington County, Virginia, USA and discharges to the Potomac River via the Four Mile Run. The ACWPCP was originally constructed in 1937. In 2001, Arlington County, Virginia (USA) committed to expanding their 113,500 m³/d, (300,000 pe) secondary treatment plant to a 151,400 m³/d (400,000 pe) to achieve effluent total nitrogen (TN) to <3 mg/l and total phosphorus (TP) < 0.18 mg/l. Key to this conversion was the implementation of deep bed denitrification filters to simultaneously achieve both low effluent TN and TP concentrations. A challenge with implementing this technology is maintaining a health denitrifying biomass within the denitrification filters while reducing an essential nutrient, phosphorus, to very low concentrations. This paper will review the steps from concept to the first year of operation, including pilot and full-scale operating data and the capital cost for the denitrification filters.