ARA Consult

Innsbruck, Austria

ARA Consult

Innsbruck, Austria

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Regmi P.,Old Dominion University | Miller M.W.,Virginia Polytechnic Institute and State University | Holgate B.,Old Dominion University | Bunce R.,Hazen and Sawyer | And 5 more authors.
Water Research | Year: 2014

This work describes the development of an intermittently aerated pilot-scale process (V=0.34m3) operated without oxidized nitrogen recycle and supplemental carbon addition optimized for nitrogen removal via nitritation/denitritation. The aeration pattern was controlled using a novel aeration strategy based on set-points for reactor ammonia, nitrite and nitrate concentrations with the aim of maintaining equal effluent ammonia and nitrate+nitrite (NOx) concentrations. Further, unique operational and process control strategies were developed to facilitate the out-selection of nitrite oxidizing bacteria (NOB) based on optimizing the chemical oxygen demand (COD) input, imposing transient anoxia, aggressive solids retention time (SRT) operation towards ammonia oxidizing bacteria (AOB) washout and high dissolved oxygen (DO) (>1.5mg/L). Sustained nitrite accumulation (NO2-N/NOx-N=0.36±0.27) was observed while AOB activity was greater than NOB activity (AOB: 391±124mgN/L/d, NOB: 233±151mgN/L/d, p<0.001) during the entire study. The reactor demonstrated total inorganic nitrogen (TIN) removal rate of 151±74mgN/L/d at an influent COD/NH4+-N ratio of 10.4±1.9 at 25°C. The TIN removal efficiency was 57±25% within the hydraulic retention time (HRT) of 3h and within an SRT of 4-8 days. Therefore, this pilot-scale study demonstrates that application of the proposed online aeration control is able to out-select NOB in mainstream conditions providing relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT. © 2014 Elsevier Ltd.


Regmi P.,Brown and Caldwell | Holgate B.,Hazen and Sawyer | Miller M.W.,Virginia Polytechnic Institute and State University | Park H.,Columbia University | And 4 more authors.
Biotechnology and Bioengineering | Year: 2016

As nitrogen discharge limits are becoming more stringent, short-cut nitrogen systems and tertiary nitrogen polishing steps are gaining popularity. For partial nitritation or nitritation-denitritation systems, anaerobic ammonia oxidation (anammox) polishing may be feasible to remove residual ammonia and nitrite from the effluent. Nitrogen polishing of mainstream nitritation-denitritation system effluent via anammox was studied at 25°C in a fully anoxic moving bed bioreactor (MBBR) (V=0.45m3) over 385 days. Unlike other anammox based processes, a very fast startup of anammox MBBR was demonstrated, despite nitrite limited feeding conditions (influent nitrite=0.7±0.59 mgN/L, ammonia=6.13±2.86mgN/L, nitrate=3.41±1.92mgN/L). The nitrogen removal performance was very stable within a wide range of nitrogen inputs. Anammox bacteria (AMX) activity up to 1gN/m2/d was observed which is comparable to other biofilm-based systems. It is generally believed that nitrate production limits nitrogen removal through AMX metabolism. However, in this study, anammox MBBR demonstrated ammonia, nitrite, and nitrate removal at limited chemical oxygen demand (COD) availability. AMX and heterotrophs contributed to 0.68±0.17 and 0.32±0.17 of TIN removal, respectively. It was speculated that nitrogen removal might be aided by denitratation which could be due to heterotrophs or the recently discovered ability for AMX to use short-chain fatty acids to reduce nitrate to nitrite. This study demonstrates the feasibility of anammox nitrogen polishing in an MBBR is possible for nitritation-denitration systems. © 2016 Wiley Periodicals, Inc.


Regmi P.,Brown and Caldwell | Holgate B.,Hazen and Sawyer | Fredericks D.,Hazen and Sawyer | Miller M.W.,Virginia Polytechnic Institute and State University | And 3 more authors.
Water Science and Technology | Year: 2015

This paper deals with an almost 1-year long pilot study of a nitritation-denitritation process that was followed by anammox polishing. The pilot plant treated real municipal wastewater at ambient temperatures. The effluent of high-rate activated sludge process (hydraulic retention time, HRT = 30 min, solids retention time = 0.25 d) was fed to the pilot plant described in this paper, where a constant temperature of 23 °C was maintained. The nitritation-denitritation process was operated to promote nitrite oxidizing bacteria out-selection in an intermittently aerated reactor. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia and nitrate + nitrite concentrations. The unique feature of this aeration control was that fixed dissolved oxygen set-point was used and the length of aerobic and anoxic durations were changed based on the effluent ammonia and nitrate + nitrite concentrations. The anaerobic ammonia oxidation (anammox) bacteria were adapted in mainstream conditions by allowing the growth on the moving bed bioreactor plastic media in a fully anoxic reactor. The total inorganic nitrogen (TIN) removal performance of the entire system was 75 ± 15% during the study at a modest influent chemical oxygen demand (COD)/NH4+-N ratio of 8.9 ± 1.8 within the HRT range of 3.1-9.4 h. Anammox polishing contributed 11% of overall TIN removal. Therefore, this pilot-scale study demonstrates that application of the proposed nitritation-denitritation system followed by anammox polishing is capable of relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT. © 2015 IWA Publishing.


Regmi P.,Brown and Caldwell | Bunce R.,Hazen and Sawyer | Miller M.W.,Virginia Polytechnic Institute and State University | Park H.,Columbia University | And 4 more authors.
Biotechnology and Bioengineering | Year: 2015

This work describes the development of an intermittently aerated pilot-scale process (V=0.45m3) operated for optimized efficient nitrogen removal in terms of volume, supplemental carbon and alkalinity requirements. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia concentration set-points. The unique feature of the ammonia-based aeration control was that a fixed dissolved oxygen (DO) set-point was used and the length of the aerobic and anoxic time (anoxic time ≥25% of total cycle time) were changed based on the effluent ammonia concentration. Unlike continuously aerated ammonia-based aeration control strategies, this approach offered control over the aerobic solids retention time (SRT) to deal with fluctuating ammonia loading without solely relying on changes to the total SRT. This approach allowed the system to be operated at a total SRT with a small safety factor. The benefits of operating at an aggressive SRT were reduced hydraulic retention time (HRT) for nitrogen removal. As a result of such an operation, nitrite oxidizing bacteria (NOB) out-selection was also obtained (ammonia oxidizing bacteria [AOB] maximum activity: 400±79mgN/L/d, NOB maximum activity: 257±133mgN/L/d, P<0.001) expanding opportunities for short-cut nitrogen removal. The pilot demonstrated a total inorganic nitrogen (TIN) removal rate of 95±30mgN/L/d at an influent chemical oxygen demand: ammonia (COD/NH4+-N) ratio of 10.2±2.2 at 25°C within the hydraulic retention time (HRT) of 4h and within a total SRT of 5-10 days. The TIN removal efficiency up to 91% was observed during the study, while effluent TIN was 9.6±4.4mgN/L. Therefore, this pilot-scale study demonstrates that application of the proposed on-line aeration control is capable of relatively high nitrogen removal without supplemental carbon and alkalinity addition at a low HRT. © 2015 Wiley Periodicals, Inc.


Jimenez J.,Brown and Caldwell | Miller M.,Virginia Polytechnic Institute and State University | Bott C.,Hampton Road Sanitation District | Murthy S.,DC Water | And 2 more authors.
Water Research | Year: 2015

The high-rate activated sludge (HRAS) process is a technology suitable for the removal and redirection of organics from wastewater to energy generating processes in an efficient manner. A HRAS pilot plant was operated under controlled conditions resulting in concentrating the influent particulate, colloidal, and soluble COD to a waste solids stream with minimal energy input by maximizing sludge production, bacterial storage, and bioflocculation. The impact of important process parameters such as solids retention time (SRT), hydraulic residence time (HRT) and dissolved oxygen (DO) levels on the performance of a HRAS system was demonstrated in a pilot study. The results showed that maximum removal efficiencies of soluble COD were reached at a DO>0.3mg O2/L, SRT>0.5 days and HRT>15min which indicates that minimizing the oxidation of the soluble COD in the high-rate activated sludge process is difficult. The study of DO, SRT and HRT exhibited high degree of impact on the colloidal and particulate COD removal. Thus, more attention should be focused on controlling the removal of these COD fractions. Colloidal COD removal plateaued at a DO>0.7mg O2/L, SRT>1.5 days and HRT>30min, similar to particulate COD removal. Concurrent increase in extracellular polymers (EPS) production in the reactor and the association of particulate and colloidal material into sludge flocs (bioflocculation) indicated carbon capture by biomass. The SRT impacted the overall mass and energy balance of the high-rate process indicating that at low SRT conditions, lower COD mineralization or loss of COD content occurred. In addition, the lower SRT conditions resulted in higher sludge yields and higher COD content in the WAS. © 2015 Elsevier Ltd.


PubMed | DC Water Authority, Virginia Polytechnic Institute and State University, ARA Consult, Brown and Caldwell and 3 more.
Type: Journal Article | Journal: Biotechnology and bioengineering | Year: 2015

This work describes the development of an intermittently aerated pilot-scale process (V=0.45m(3) ) operated for optimized efficient nitrogen removal in terms of volume, supplemental carbon and alkalinity requirements. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia concentration set-points. The unique feature of the ammonia-based aeration control was that a fixed dissolved oxygen (DO) set-point was used and the length of the aerobic and anoxic time (anoxic time 25% of total cycle time) were changed based on the effluent ammonia concentration. Unlike continuously aerated ammonia-based aeration control strategies, this approach offered control over the aerobic solids retention time (SRT) to deal with fluctuating ammonia loading without solely relying on changes to the total SRT. This approach allowed the system to be operated at a total SRT with a small safety factor. The benefits of operating at an aggressive SRT were reduced hydraulic retention time (HRT) for nitrogen removal. As a result of such an operation, nitrite oxidizing bacteria (NOB) out-selection was also obtained (ammonia oxidizing bacteria [AOB] maximum activity: 40079mgN/L/d, NOB maximum activity: 257133mgN/L/d, P<0.001) expanding opportunities for short-cut nitrogen removal. The pilot demonstrated a total inorganic nitrogen (TIN) removal rate of 9530mgN/L/d at an influent chemical oxygen demand: ammonia (COD/NH4 (+) -N) ratio of 10.22.2 at 25C within the hydraulic retention time (HRT) of 4h and within a total SRT of 5-10 days. The TIN removal efficiency up to 91% was observed during the study, while effluent TIN was 9.64.4mgN/L. Therefore, this pilot-scale study demonstrates that application of the proposed on-line aeration control is capable of relatively high nitrogen removal without supplemental carbon and alkalinity addition at a low HRT.


PubMed | DC Water Authority, Virginia Polytechnic Institute and State University, ARA Consult, Brown and Caldwell and 3 more.
Type: Journal Article | Journal: Biotechnology and bioengineering | Year: 2016

As nitrogen discharge limits are becoming more stringent, short-cut nitrogen systems and tertiary nitrogen polishing steps are gaining popularity. For partial nitritation or nitritation-denitritation systems, anaerobic ammonia oxidation (anammox) polishing may be feasible to remove residual ammonia and nitrite from the effluent. Nitrogen polishing of mainstream nitritation-denitritation system effluent via anammox was studied at 25C in a fully anoxic moving bed bioreactor (MBBR) (V=0.45m(3) ) over 385 days. Unlike other anammox based processes, a very fast startup of anammox MBBR was demonstrated, despite nitrite limited feeding conditions (influent nitrite=0.70.59 mgN/L, ammonia=6.132.86mgN/L, nitrate=3.411.92mgN/L). The nitrogen removal performance was very stable within a wide range of nitrogen inputs. Anammox bacteria (AMX) activity up to 1gN/m(2) /d was observed which is comparable to other biofilm-based systems. It is generally believed that nitrate production limits nitrogen removal through AMX metabolism. However, in this study, anammox MBBR demonstrated ammonia, nitrite, and nitrate removal at limited chemical oxygen demand (COD) availability. AMX and heterotrophs contributed to 0.680.17 and 0.320.17 of TIN removal, respectively. It was speculated that nitrogen removal might be aided by denitratation which could be due to heterotrophs or the recently discovered ability for AMX to use short-chain fatty acids to reduce nitrate to nitrite. This study demonstrates the feasibility of anammox nitrogen polishing in an MBBR is possible for nitritation-denitration systems.


PubMed | DC Water Authority, Virginia Polytechnic Institute and State University, ARA Consult, Brown and Caldwell and 2 more.
Type: Journal Article | Journal: Water science and technology : a journal of the International Association on Water Pollution Research | Year: 2015

This paper deals with an almost 1-year long pilot study of a nitritation-denitritation process that was followed by anammox polishing. The pilot plant treated real municipal wastewater at ambient temperatures. The effluent of high-rate activated sludge process (hydraulic retention time, HRT=30 min, solids retention time=0.25 d) was fed to the pilot plant described in this paper, where a constant temperature of 23 C was maintained. The nitritation-denitritation process was operated to promote nitrite oxidizing bacteria out-selection in an intermittently aerated reactor. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia and nitrate+nitrite concentrations. The unique feature of this aeration control was that fixed dissolved oxygen set-point was used and the length of aerobic and anoxic durations were changed based on the effluent ammonia and nitrate+nitrite concentrations. The anaerobic ammonia oxidation (anammox) bacteria were adapted in mainstream conditions by allowing the growth on the moving bed bioreactor plastic media in a fully anoxic reactor. The total inorganic nitrogen (TIN) removal performance of the entire system was 7515% during the study at a modest influent chemical oxygen demand (COD)/NH4+-N ratio of 8.91.8 within the HRT range of 3.1-9.4 h. Anammox polishing contributed 11% of overall TIN removal. Therefore, this pilot-scale study demonstrates that application of the proposed nitritation-denitritation system followed by anammox polishing is capable of relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT.


PubMed | Hampton Road Sanitation District, DC Water, Virginia Polytechnic Institute and State University, ARA Consult and Brown and Caldwell
Type: | Journal: Water research | Year: 2015

The high-rate activated sludge (HRAS) process is a technology suitable for the removal and redirection of organics from wastewater to energy generating processes in an efficient manner. A HRAS pilot plant was operated under controlled conditions resulting in concentrating the influent particulate, colloidal, and soluble COD to a waste solids stream with minimal energy input by maximizing sludge production, bacterial storage, and bioflocculation. The impact of important process parameters such as solids retention time (SRT), hydraulic residence time (HRT) and dissolved oxygen (DO) levels on the performance of a HRAS system was demonstrated in a pilot study. The results showed that maximum removal efficiencies of soluble COD were reached at a DO > 0.3 mg O2/L, SRT > 0.5 days and HRT > 15 min which indicates that minimizing the oxidation of the soluble COD in the high-rate activated sludge process is difficult. The study of DO, SRT and HRT exhibited high degree of impact on the colloidal and particulate COD removal. Thus, more attention should be focused on controlling the removal of these COD fractions. Colloidal COD removal plateaued at a DO > 0.7 mg O2/L, SRT > 1.5 days and HRT > 30 min, similar to particulate COD removal. Concurrent increase in extracellular polymers (EPS) production in the reactor and the association of particulate and colloidal material into sludge flocs (bioflocculation) indicated carbon capture by biomass. The SRT impacted the overall mass and energy balance of the high-rate process indicating that at low SRT conditions, lower COD mineralization or loss of COD content occurred. In addition, the lower SRT conditions resulted in higher sludge yields and higher COD content in the WAS.


Jiang D.,Columbia University | Khunjar W.O.,Columbia University | Wett B.,ARA Consult | Murthy S.N.,DC Water | Chandran K.,Columbia University
Environmental Science and Technology | Year: 2015

The link between the nitrogen and one-carbon cycles forms the metabolic basis for energy and biomass synthesis in autotrophic nitrifying organisms, which in turn are crucial players in engineered nitrogen removal processes. To understand how autotrophic nitrifying organisms respond to inorganic carbon (IC) conditions that could be encountered in engineered partially nitrifying systems, we investigated the response of one of the most extensively studied model ammonia oxidizing bacteria, Nitrosomonas europaea (ATCC19718), to three IC availability conditions: excess gaseous and excess ionic IC supply (40× stoichiometric requirement), excess gaseous IC supply (4× stoichiometric requirement in gaseous form only), and limiting IC supply (0.25× stoichiometric requirement). We found that, when switching from excess gaseous and excess ionic IC supply to excess gaseous IC supply, N. europaea chemostat cultures demonstrated an acclimation period that was characterized by transient decreases in the ammonia removal efficiency and transient peaks in the specific oxygen uptake rate. Limiting IC supply led to permanent reactor failures (characterized by biomass washout and failure of ammonia removal) that were preceded by similar decreases in the ammonia removal efficiency and peaks in the specific oxygen uptake rate. Notably, both excess gaseous IC supply and limiting IC supply elicited a previously undocumented increase in nitric and nitrous oxide emissions. Further, gene expression patterns suggested that excess gaseous IC supply and limiting IC supply led to consistent up-regulation of ammonia respiration genes and carbon assimilation genes. Under these conditions, interrogation of the N. europaea proteome revealed increased levels of carbon fixation and transport proteins and decreased levels of ammonia oxidation proteins (active in energy synthesis pathways). Together, the results indicated that N. europaea mobilized enhanced IC scavenging pathways for biosynthesis and turned down respiratory pathways for energy synthesis, when challenged with excess gaseous IC supply and limiting IC supply. © 2014 American Chemical Society.

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