End Of Nitrification Research Articles

Performance of A2NO-MBR process in treating synthetic and municipal wastewater.

In this study, a novel anaerobic-anoxic/nitrification (A2N) two-sludge sequencing batch reactor (SBR) configured with post-aeration (A2NO-membrane bioreactor process) was conducted to evaluate the operational efficiency, process characteristics, and microbial community structure in treating synthetic and municipal wastewater. When influent C/N ratios were 4.2-8.6, the removal efficiencies of COD, NH4+-N, TN, and TP were 86.4-90.0, 85.2-93.6, 61.8-76.0, and 97.6-99.3%, respectively, and the effluent concentrations met the first level A criteria of GB18918-2002. Phosphorus removal was mainly in anoxic phase with a removal rate of 0.54-1.30mgP/(gMLSSh), accounting for 75.9-99.7%. Enhanced phosphorus removal was observed during post-aeration phase with a removal rate of 0.06-0.55mgP/(gMLSSh). Additionally, Oxidation-Reduction Potential (ORP) and pH could reflect the process of anaerobic phosphorus release and anoxic denitrifying phosphorus removal. DO and pH could indicate the end of nitrification. Moreover, Candidatus Accumulibacter and Dechloromonas related to biological nitrogen and phosphorus removal were enriched effectively with total proportions of 15.9 and 11.5% in treating synthetic and municipal wastewater, respectively.

Real-Time Control System Based on the Values of Derivative of the Redox Potential Aiming Nitrogen Removal in a Sequencing Batch Reactor Applied in Treating Dairy Wastewater

This paper presents a real-time control strategy based on the derivative of the oxi-reduction potential (ORP) values for nitrogen removal via nitrite in a sequencing batch reactor (SBR) fed with effluent from an anaerobic sequencing batch reactor (ASBR) treating dairy wastewater. The developed control strategy optimized the length of aerobic and anoxic phases without external carbon source addition. Firstly, a fixed interval length for aeration period was used in the SBR cycle to promote the nitrogen removal; however, this strategy did not allow the proper alternation of anoxic and aerobic conditions, and thus effective removal of nitrogen was not verified. After that, the real-time control strategy was implemented, and the end of nitrification and denitrification processes was determined when the derivative of the oxi-reduction potential (ORP) was close to zero. This strategy provided a removal of 92.2 ± 9.7 and 63.9 ± 19.0% for concentrations of TKN-N and Nt-N, respectively, which were well above those found for the open-loop system—43.8 ± 21.6 and 26.5 ± 26.2% for the removal of TKN-N and Nt-N, respectively.

Impact of N2O Emissions on Nitritation in Two Sequencing Batch Reactors: Activated Sludge Reactor and Biofilm System

Abstract The objective of this study was to evaluate nitrous oxide (N2O) emissions on nitritation in activated sludge sequencing batch reactor (ASSBR) and sequencing batch biofilm reactor (SBBR) treating ammonium-rich wastewater at two different influent ammonium concentrations. During stable operation, there was no significant difference of \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $${ \rm NH}_4^ + { {\hbox {-}} { \rm N}}$$ \end{document} removal efficiencies between the two reactors. At the end of nitrification, both nitrite accumulation rates were above 85%. However, SBBR had a better total nitrogen (TN) removal efficiency (81.7% ± 1.5%) than that of ASSBR (66.5% ± 5.7%). According to typical cycles, when influent \documentclass{aastex}\usepackage{...

Actuators monitoring system for real-time control of nitrification–denitrification via nitrite on long term operation

A real-time control strategy for SBR was designed in order to control the length of the reaction phases for an integrated nitrification–denitrification process via nitrite, by using an actuators monitoring system instead of monitoring pH or oxygen signals. The real-time control strategy was validated during 220days at a low dissolved oxygen concentration (1–2.0mg/L), C/N ratio of 1–2g COD/gN, and at initial ammonia nitrogen concentrations in a range of 50–600mgN/L. The aerobic reaction was conducted under control of pH and dissolved oxygen concentration and their manipulated variables: air valve opening and inorganic carbon consumption were used to detect bending points and the end of nitrification, whereas ORP and pH curves were used to detect the end of denitrification. This strategy led to a removal of total nitrogen over 94%, with a nitrite accumulation of 80% and a simultaneous nitrification denitrification of up to 60%. Additionally, a dosage strategy of adding external carbon during denitrification was developed by evaluating the pH derivative, and it was found that the anoxic time was able to reach values as low as 8% of the total reaction time.

Seasonally varying nitrogen isotope biogeochemistry of particulate organic matter in Lake Kinneret, Israel

Large temporal variations in the nitrogen isotopic composition (δ15N) of particulate organic matter (POM) and dissolved inorganic nitrogen (DIN) species in Lake Kinneret occurred in response to seasonal phasing of dominant nitrogen cycle processes. The lowest δ15N POM values (25.5‰) were observed in early winter, a consequence of isotopic fractionation by chemoautotrophic microbial NH4+ assimilation, and during the first phase of the nitrification period, by seasonally dominant NH4+ oxidizers. Nitrification itself was strongly fractionating, producing 15N-depleted NO3− and strongly enriching water-column NH4+ in 15N. Toward the end of nitrification and into the phytoplankton bloom period in later winter and early spring, there was a corresponding 15-30‰ jump in POM δ15N because of assimilation of high-δ15N NH4+. Maximal δ15N POM values were thus measured during the algal blooms of Peridinium gatunense in 2004 and Debarya sp. and Microcystis sp. in 2005. Toward the end of the blooms in mid- to late spring, POM δ15N values decreased to values similar to δ15N for NO3− (8-12‰), indicating a switch to this DIN source. NO3− assimilation into POM appeared to occur without isotopic fractionation. Late spring was also the denitrification period with NO3− removal in the newly suboxic hypolimnion. Though δ15NO3− increased in the residual NO3−, complete consumption by denitrification suggests no net effect, as supported by a lack of increase in δ15N POM at this time. Oligotrophic conditions are found in the epilimnion in late summer and early autumn and low (3.3‰) δ15N POM was found during the bloom of the filamentous N2-fixing cyanobacteria Aphanizomenon ovalisporum and Cylindrospermopsis cuspis. The δ15N-dissolved organic nitrogen isotopic signature at this time was significantly higher, 8–12‰, suggesting a phytoplankton source from earlier in the seasonal cycle. Overall, the largest known seasonal variations in N isotope composition have been observed in Lake Kinneret, providing a uniquely useful biogeochemical tool for studying N cycling in lakes as well as detecting long-term changes in N source and cycling in response to watershed land use changes and climate change.

Nitrogen removal from pharmaceutical manufacturing wastewater with high concentration of ammonia and free ammonia via partial nitrification and denitrification

In this study, laboratory-scale experiments were conducted applying a Sequencing Batch Reactor (SBR) activated sludge process to a wastewater stream from a pharmaceutical factory. Nitrogen removal can be achieved via partial nitrification and denitrification and the efficiency was above 99% at 23 degrees C+/-1. The experimental results indicated that the nitrite oxidizers were more sensitive than ammonia oxidizers to the free ammonia in the wastewater. The average accumulation rate of nitrite was much higher than that of nitrate. During nitrogen removal via the nitrite pathway, the end of nitrification and denitrification can be exactly decided by monitoring the variation of pH. Consequently, on-line control for nitrogen removal from the pharmaceutical manufacturing wastewater can be achieved and the cost of operation can be reduced.

Applicability of Oxidation Reduction Potential Response on a Full-Scale Intermittently Aerated Suspended Culture System

On-line monitoring of oxidation reduction potential (ORP) was conducted at the full-scale aeration basin operated with intermittent aeration schedules and fed with the wastewater generated from fruit fly rearing facility owned by the California Department of Food and Agriculture, Waimanalo, Hawaii. The characteristics of the wastewater were fluctuated, severely. The 90 percentile level of total chemical oxygen demand, total Kjeldahl nitrogen, and total suspended solids for the wastewater are 5,200, 142, and 3,350 mg/L, respectively. Two aeration schedules of 4 h aeration/2 h nonaeration and 3 h aeration/3 h nonaeration were investigated in this study. Typical ORP curve with bending points of β (beginning of denitrification), χ (disappearance of nitrate), and plateau (dORP/dt=0) were observed for both aeration schedules. The α (end of nitrification) value couldn’t detect in the aeration schedule of 3 h aeration/3 h nonaeration because of the ORP fluctuation at the onset of aeration. However, the α value detected without any difficulty for the aeration schedule of 4 h aeration/2 h nonaeration. This is due to the relatively lower gradient of the reduced substance concentration between supernatant and settled sludge layers during the air-off period. Through the ORP monitoring of the full-scale aeration basin treating fruit fly rearing facility wastewater, the aeration time can be reduced from 4 h to 3 h without deterioration of organic and nitrogen removal efficiencies. By reducing the aeration time, 25% of energy cost for aeration can be saved. From the result of real time monitoring of ORP response and water quality analysis of nitrogen, the behaviors of nitrogen forms are closely related to the ORP response. Therefore, the ORP monitoring is a practical and easy tool for the evaluation of the degree of nitrification and denitrification condition in biological wastewater-treatment systems.

Use of pH as fuzzy control parameter for nitrification under different alkalinity in SBR process

In order to achieve fuzzy control of nitrification in a Sequencing Batch Reactor (SBR) brewery wastewater was used as the substrate. The effect of alkalinity on pH variation during nitrification was systematically studied, at the same time the variations of DO and ORP were investigated. Alkalinity and pH of the wastewater were adjusted by adding sodium bicarbonate at five levels and sodium hydroxide at two levels. Unadjusted wastewater was also studied. According to the results, variation of pH could be divided into rising type and descending type. When bicarbonate alkalinity was deficient or sufficient, the descending type happened. If alkalinity was deficient, the pH decreasing rate got slower when nitrification nearly stopped; if alkalinity was sufficient, at the end of nitrification pH turned from decrease to increase. This was the most common situation and pH could be used to control the end of nitrification. When alkalinity was excessive, the rising type happened, pH was increasing at nearly a constant rate during and after nitrification and could not be used to control the nitrification time, but if the aeration rate was moderate DO could be used to control the nitrification time. This situation seldom happened. Therefore the variation of pH could not only be used to control the nitrification time but also to judge whether the alkalinity was enough or not. On the basis of this, the fuzzy controller of nitrification in SBR was constructed. When discussing the influence of pH on nitrification rate the composition and concentration of alkalinity must be considered or else the results may be incomprehensive. And to some extent the influence of alkalinity on nitrification rate was more important than pH.

PH and Oxidation–Reduction Potential Control Strategy for Optimization of Nitrogen Removal in an Alternating Aerobic–Anoxic System

An alternating aerobic and anoxic (AAA) system is a continuous-flow, activated-sludge process in which the environmental conditions necessary to meet the specific requirements for aerobic nitrification and anoxic denitrification are created. Because of stricter regulations on wastewater effluent and concerns on energy consumption, the process control of the system is now becoming more important. A bench-scale AAA system with different fixed aeration ratios was operated for more than 8 months to evaluate effects of the total cycle time and aeration ratio on the system performance and to develop a feasible control scheme. With supplemental organic addition, the system shows removal efficiencies of 85 to 90% and 78 to 82% for chemical oxygen demand and total nitrogen, respectively. The oxidation-reduction potential (ORP) and pH profiles indicate that the aerobic cycle can be controlled by a control point (ammonia valley) on the pH profile indicating the end of nitrification and the anoxic cycle controlled by another point (nitrate knee) on the ORP profile signifying the end of denitrification. Thus, a dual control strategy with the pH and ORP control points was used for terminating aerobic-anoxic and initiating anoxic-aerobic cycles in an AAA system. The performance of the online control system is excellent, with a significant energy saving (average aeration ratio, fa = 0.23) as compared to the fixed time systems (fa = 0.33 to approximately 0.5).

Sequencing Batch Reactor System for Nutrient Removal: ORP and pH Profiles

The sequencing batch reactor (SBR) process is known for its flexibility to meet a wide range of treatment needs, including nutrient removal. However, information related to the operational stability of SBR nutrient removal systems and control parameters to adjust the cyclic duration is sparse. Consequently, this study was undertaken to identify process parameters (pH and oxidation reduction potential) that could be useful for monitoring and real-time control purposes. In general, the system achieved removal efficiencies of 91, 98 and 98%, respectively, for Chemical Oxygen Demand, total nitrogen and phosphate at the solids retention time of 10 days, with a cyclic duration of 6 h. Shock loadings of nitrogen (20 mg dm -3 of NH 4 + -N, four cycles) exhibited little impact on effluent quality, except for a higher nitrate content. Activated sludge settled well throughout the entire study period. Several significant points associated with different reactions within SBR cycle, e.g. end of nitrification, end of phosphate release and completion of phosphate uptake, were identified in pH profiles. Slope changes in pH profiles (dpH/dt, or d 2 pH/dt 2 ) were found to better represent the corresponding biological reactions. The application of these significant points in pH profiles as real time control parameters appears promising.