Supplementary Aeration Research Articles

The effect of aeration on treatment efficiency and bioenergy generation of septic-tank effluent in constructed wetland-microbial fuel cell

This study examines the effect of different rates and modes of supplementary aeration on the treatment of synthetic septic tank effluent in a lab-scale unplanted constructed wetland-microbial fuel cell (CW-MFC) along with bioenergy generation. The experiment was conducted in 4 sequential phases; 1) the cell was operated with no aeration (NA), 2&3) the cathode layer was continuously aerated under different aeration rates (CA-I and CA-II), and 4) the cathode layer was intermittently aerated (IA). Results showed that the dissolved oxygen gradient caused by IA formed aerobic and anoxic zones in CW-MFC and promoted total nitrogen removal. The best performance was observed with intermittent aeration where the maximum removal efficiencies of COD (96.8 ± 3.3 %), TN (62.3 ± 2.1 %), TKN (68.3 ± 2.0 %), and NH3 (64.8 ± 2.3 %) were achieved. Furthermore, this treatment efficiency corresponded with enhanced bioenergy generation under the IA regime, achieving maximum power output (7.5 mW/m2), highest average voltage output (0.399 ± 0.02 V), Coulombic efficiency (1.94 %), and normalized energy recovery (1.4 Wh/m3). Continuous aeration, however, induced an adverse effect on energy generation due to excessive oxygen penetration into the anode region. Nitrate accumulation was also observed as a sign of an incomplete denitrification process under the continuous aeration regime. Overall, it can be concluded that the intermittently aerated CW-MFC not only lowers operational costs but improves effectiveness in terms of the nitrogen removal process in the treatment of septic tank effluent.

Caffeine-containing wastewater treatment and bioelectricity generation in up-flow constructed wetland-microbial fuel cell: Influence of caffeine concentration, operating conditions, toxicity assessment, and degradation pathway

This study explored the potential of caffeine being utilized as the fuel for the microbes to produce electrons for electricity generation in up-flow constructed wetland-microbial fuel cell (UFCW-MFC). The effect of caffeine concentration was investigated to identify the availability of UFCW-MFC in the conversion of caffeine to electrons for electricity production; and the effect of operating conditions (circuit connection, supplementary aeration, and plant) was studied to determine their significance in the treatment of caffeine containing wastewater. The UFCW-MFC achieved about 98% of decaffeination efficiency regardless of caffeine concentration; while a decrease of efficiency was observed when UFCW-MFC operated without supplementary aeration and plant (~93%). COD removal efficiency decreased correspondingly to the increase of caffeine concentration, which could be contributed by the higher concentration of caffeine and its intermediates. The degradation pathway of caffeine in UFCW-MFC was explored in this study. It was remarkable that ammonia was produced and converted to ammonium ions during caffeine catabolism. Supplementary aeration and macrophyte play a crucial role in removing excess caffeine, intermediates as well as accumulated ammonium ions. The toxicity assessment revealed that caffeine was degraded to less toxic products. The closed circuit connection not only contributed to electricity generation but also enhanced the caffeine and COD removal efficiency by 4.6 and 5.4% in the anaerobic region, respectively. The increase of voltage and maximum power density from phase I to phase IV indicated that caffeine could be converted to electrons by the anaerobes for electricity production.

Effect of biofloc technology on growth performance, digestive enzyme activity, proximate composition, and hematological parameters of Asian stinging catfish (Heteropneustes fossilis)

ABSTRACT This investigation aimed to evaluate the effects of the biofloc system on growth, digestive activity, proximate composition, and hematology of Asian stinging catfish for 120 days. Fingerlings (n = 2,700; 4.40 ± 0.10 g) were randomly distributed in six outdoor circular tanks (3,000 L) with supplementary aeration and hand-fed with a commercial diet (35% CP) at 5%–2% of the biomass in the control group and 2%–1% in the biofloc group (sugarcane molasses) to establish a (C/N) ratio 10:1. Ammonia, nitrate, nitrite, and total suspended solids were significantly lower in the BFT than in the control (P < 0.05). Suspended floc significantly ameliorates mean weight gain, percent weight gain, mean total biomass, specific growth rate, and feed utilization compared to the control (P < 0.05). Protease and amylase activity in the intestine and liver lipase activity of fish were found to be significantly higher in the biofloc group (P < 0.05). An improved hematological profile was observed in the biofloc groups (P < 0.05). The crude protein and lipid content was also higher in the biofloc system than in the control. This study indicates that biofloc would be the best alternative approach for sustainable aquaculture production of Asian singing catfish.

Integration of CW-MFC and anaerobic granular sludge to explore the intensified ammonification-nitrification-denitrification processes for nitrogen removal

The integration of constructed wetland-microbial fuel cell (CW-MFC) and anaerobic granular sludge (AGS) is an important way to promote its ammonification efficiency and decrease the land use scale. This study explored the integration of CW-MFC and AGS for nitrogen removal via the intensified ammonification-nitrification-denitrification processes with initial NH3–N, NO3–N, Org-N and total nitrogen (TN) concentrations of 10.5, 13.8, 21.4, and 45.7 mg L−1 in wastewater. Two reactors with AGS inoculated with a separated area (R1) and directly inoculated into gravel substrate (R2) were designed, respectively. Results showed that chemical oxygen demand (COD) removal efficiency could reach 85% in R1 and 81% in R2, and the conversion of Org-N to NH3–N and NO3–N to gaseous nitrogen were 80% and 90%, respectively. Although the conversion efficiency of NH3–N to NO2–N/NO3–N via nitrification process was only 18%, it could reach 45%, 94%, and 98% with the aeration rates of 50-, 100-, and 200-mL min−1. According to microstructural property and microbial community analyses, the separation gravel substrate and AGS areas in R1 availed for stable particle size of AGS, archaeal diversity, and metabolic activity even with a 1.5 times daily wastewater treatment capacity than that of R2. Overall, although the intensified ammonification-nitrification-denitrification processes for nitrogen removal could be achieved with supplementary aeration, further investigation is still needed to explore other substrate materials and high CW-MFC/AGS volume ratio for intensified nitrification process in CW-MFC associated with AGS.

Up-flow constructed wetland-microbial fuel cell: Influence of floating plant, aeration and circuit connection on wastewater treatment performance and bioelectricity generation

The influence of floating plant (Eichhornia crassipes), supplementary aeration and circuit connection on wastewater treatment performance and electricity production using up-flow constructed wetland-microbial fuel cell (UFCW-MFC) were investigated in this study. This study was operated for four stages, where stage I was conducted without plant and aeration; stage II was planted with Eichhornia crassipes; supplementary aeration was provided in stage III; stage IV was operated in open circuit. The supplementary aeration showed the most significant effect on the performance of UFCW-MFC compared to floating plant and circuit connection. The optimum performance of wastewater treatment and electricity production was found in stage III as the oxygen was supplied by the floating plant and supplementary aeration for the degradation of organic matters as well as the generation of bioelectricity. The chemical oxygen demand (COD), NH4+ and NO3− removal efficiencies were 99 %, 96 % and 44 %, respectively. E. crassipes and supplementary aeration improved the dissolved oxygen (DO) concentration at the cathodic region and enhanced the NH4+ removal by 10 % (Stage II) and 67 % (Stage III) compared to the non-planted bioreactor (stage I). Closed circuit also performed 6 % better than open circuit at sampling point 1 (S1) in COD reduction. The maximum power density, voltage output, coulombic efficiency and normalized energy recovery were 45.46 ± 3.83 mW/m3, 291 ± 62 mV, 2.15 %, 15.09 Wh/kg COD and 0.31 W/m3, respectively.

Effect of feeding frequency on water quality, growth, and hematological parameters of Nile tilapia Oreochromis niloticus reared using biofloc technology

ABSTRACT The aim of this study was to evaluate the effect of feeding frequency on water quality, growth performance, feed efficiency, and hematological parameters of Nile tilapia reared in biofloc technology (BFT) over a period of 45 days. Fish (n = 6,480; 5.36 ± 1.45 g) were randomly distributed in nine outdoor circular tanks (9,000 L) with individual air-water lift by supplementary aeration and hand-fed with commercial diet (32% crude protein) at 5-3% of biomass, following the respective feeding frequencies: two times per day, four times per day, and six times per day. The experimental design was completely randomized with three treatments and three replicates. Feeding frequency at four times per day decreased rotifer density and improved (P < .05) the weight gain and protein efficiency ratio. No significant differences were observed in hematological parameters. Water quality remained within recommended ranges for tilapia culture. Turbidity and floc volume showed significant differences (P < .05) among treatments, with the greatest concentrations at six times per day. Feeding frequency at four times per day promoted the best growth and feed efficiency responses in Nile tilapia (5 - 20 g)cultured in BFT.

Bioeconomic profitability analysis of tropical gar (Atractosteus tropicus) grow out using two commercial feeds

This study compared survival, growth, feed conversion rate (FCR) and harvested biomass of two commercial strains of tilapia ( Oreochromis niloticus ) cultivated in Mexico: Spring Genetic-Benchmark Holding® originated from the Genetically Improved Farmed Tilapia GIFT (Genebank: GIFT GU477624.1) and strain B from different line-breeding (Genebank: Philippines GU477626.1, Guangdong GU477627.1, and America GU477628.1). The study was performed in six geomembrane ponds (2,520 m 3 ; 30×40×1.5 m) with supplementary aeration, in Los Pozos farm, El Rosario, Sinaloa, Mexico. In July 2016, 26,762 ± 170 fries of each strain (2.9 ± 0.1 g and 5.4 ± 0.2 cm) were cultivated in the nursery under similar conditions in triplicate at 11 ind m -3 for 34 days; then, they were transferred to the grow-out ponds and fed with 30% crude protein balanced feed (Purina®) at a rate of 12% live weight day -1 in three rations (07:00, 12:00 and 17:00 h) for 123 days. The results showed that Spring had a lower variation coefficient (VC) and higher survival, growth rate in weight, initial and final size, and harvested biomass. Survival was 30.7% greater in Spring and doubled harvested biomass (Spring 10 ± 0.8 t ha -1 vs. B strain 5 ± 4.7 t ha -1 ). Sixty percent of the Spring population reached a commercial weight of 500 g in day 123th of cultivation compared with 20% of B population in the same period. Except for FCR, VC was lower in the Spring strain. Differences in productive parameters were probably due to the genetic selection programs at which both strains were subjected.

Enhancement of wastewater treatment efficiency through modulation of aeration and blue light on wastewater-borne algal-bacterial consortia

Since few studies have investigated the nitrification and assimilation of nitrogens by algal-bacterial consortia, this study aimed to evaluate the effects of supplementary aeration and blue light on nitrogen removal and biomass growth of algal-bacterial consortia in real domestic wastewater. When blue light was weakly irradiated (500 μmol m−2 s−1), it was found that supplementary aeration enhanced ammonia removal from 38.5% to 96.3% and algal growth from 72.5 mg algae L−1 to 345.3 mg algae L−1 by providing oxygen for nitrification and inorganic carbon for photosynthesis of microalgae. It was also observed that ammonia was consumed first and then nitrate produced by nitrification was assimilated, indicating that diauxic growth of consortia on nitrogen sources occurred. Thus, it was expected that nitrogen removal could be enhanced by lowering nitrification and denitrification loads. Moreover, intense blue light was found to accumulate nitrite by selective photoinhibition of nitrite oxidizing bacteria (NOB) of which c-type cytochrome is known to be photo-bleachable at 408 nm. From these results, it was concluded that favorable conditions for growth and nitrogen removal by algal-bacterial consortia in real wastewater could be established by controlling aeration and light intensity.

Simultaneous boron (B) removal and electricity generation from domestic wastewater using duckweed-based wastewater treatment reactors coupled with microbial fuel cell

Boron removal from water environment is a critical issue for scientific spotlight because its removal from wastewater is difficult and costly with conventional treatment method. Herein, an innovative, cost effective and attractive method which depends on duckweed-based wastewater treatment systems coupled with microbial fuel cell reactor (DWWT-MFC) was investigated for B-polluted domestic wastewater treatment and simultaneous electricity generation for the first time in an eco-technological study. Lemna gibba L. was selected as a model duckweed species, and different reactors were also designed to identify which mechanisms are dominant for B removal in a DWWT-MFC reactor matrix. DWWT-MFC reactor achieved 71% B removal in experiment period, and the plant effect on B removal mechanisms in the reactor matrix was recorded as 37.7 ± 4.92% (F = 2.543, p < 0.05). However, supplementary aeration and microbial effects on B removal were determined as negligible. Average maximum voltage output was found as 1.47 V, and maximum power density was 34.8 mW/m2 at a current density of 43.9 mA/m2 with supplementary aeration. Moreover, DWWT-MFC reactor achieved 84%, 81% and 76% of COD, NH4+ and PO43− removal efficiencies, respectively. Moreover, L. gibba grew well in the anode chamber of DWWT-MFC with an average biomass yield of 218 ± 43 g/m2 and a total chlorophyll (a+b) concentration of 30.2 mg g−1, which indicates that anolyte environment was not toxic for L. gibba growth. Consequently, it can be suggested that environmental experts may use DWWT-MFC as an efficient removal method to treat B from domestic wastewater and to produce bioelectricity.

Decolorization and mineralization of Amaranth dye using multiple zoned aerobic and anaerobic baffled constructed wetland

ABSTRACTThe objective of this study is to determine the reduction efficiency of Chemical Oxygen Demand (COD) as well as the removal of color and Amaranth dye metabolites by the Aerobic–anaerobic Baffled Constructed Wetland Reactor (ABCW). The ABCW reactor was planted with common reed (Phragmite australis) where the hydraulic retention time (HRT) was set to 1 day and was fed with synthetic wastewater with the addition of Amaranth dye. Supplementary aeration was supplied in designated compartments of the ABCW reactor to control the aerobic and anaerobic zones. After Amaranth dye addition the COD reduction efficiency dropped from 98 to 91% while the color removal efficiency was 100%. Degradation of azo bond in Amaranth dye is shown by the UV–Vis spectrum analysis which demonstrates partial degradation of Amaranth dye metabolites. The performance of the baffled unit is due to the longer pathway as there is the up-flow and down-flow condition sequentially, thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones.

Role of macrophyte and effect of supplementary aeration in up-flow constructed wetland-microbial fuel cell for simultaneous wastewater treatment and energy recovery

This study investigates the role of plant (Elodea nuttallii) and effect of supplementary aeration on wastewater treatment and bioelectricity generation in an up-flow constructed wetland-microbial fuel cell (UFCW-MFC). Aeration rates were varied from 1900 to 0mL/min and a control reactor was operated without supplementary aeration. 600mL/min was the optimum aeration flow rate to achieve highest energy recovery as the oxygen was sufficient to use as terminal electron acceptor for electrical current generation. The maximum voltage output, power density, normalized energy recovery and Coulombic efficiency were 545.77±25mV, 184.75±7.50mW/m3, 204.49W/kg COD, 1.29W/m3 and 10.28%, respectively. The variation of aeration flow rates influenced the NO3− and NH4+ removal differently as nitrification and denitrification involved conflicting requirement. In terms of wastewater treatment performance, at 60mL/min aeration rate, UFCW-MFC achieved 50 and 81% of NO3− and NH4+ removal, respectively. E. nuttallii enhanced nitrification by 17% and significantly contributed to bioelectricity generation.

Multiple aerobic and anaerobic baffled constructed wetlands for simultaneous nitrogen and organic compounds removal

The objective of this study is to determine the reduction efficiency of chemical oxygen demand (COD) as well as the removal of NH4+-N and NO3--N by the Aerobic–anaerobic Baffled Constructed Wetland Reactor (ABCW). The ABCW reactor was planted with common reed (Phragmite australis), where the hydraulic retention times was set to 1 d and was fed with synthetic wastewater. Supplementary aeration was supplied in designated compartments of the ABCW reactor to control the aerobic and anaerobic zones. The COD reduction efficiency was 98%, while the NO3--N and NH4+-N removal was 36–98%, respectively, which was due to nitrification and denitrification processes. The outstanding performance of the baffled unit was due to the longer pathway as there is the up-flow and down-flow condition sequentially, thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones.

Removal of nitrogen from MBT residues by leachate recirculation in combination with intermittent aeration

Mechanical-biological treatment (MBT) techniques have been used to reduce the emission potential of waste before placement in landfills for a couple of years, especially in Europe. The main focus of MBT is on the reduction of native organic substances and not on nitrogen compounds. As a result, the concentrations of organic substances in leachate from MBT landfills are considerably reduced in comparison to leachates from municipal solid waste landfills, while the ammonia nitrogen concentrations remain at a high level. From the stabilization of old landfills it is well known that recirculation of leachate and supplementary aeration can reduce emissions to an acceptable level in a comparatively short time. In a series of laboratory-scale tests the efficiency of this technique for MBT residues was investigated under different boundary conditions. While the effect of leachate recirculation is also well known for MBT residues, the additional aeration has so far not been investigated. The results show that this technique has only a limited influence on the reduction of organic carbon compounds. In view of nitrogen compounds, only the additional aeration during recirculation shows a strong effect on the quality of leachate, in which the concentrations of ammonium and total nitrogen are reduced by more than 90%. The results indicate that by using simple techniques the long-term emission behavior of MBT residues can be quickly reduced to an acceptable level.

Modeling evaluation of integrated strategies to meet proposed dissolved oxygen standards for the Chicago waterway system

The Chicago Waterway System (CWS) is a 113.8 km branching network of navigable waterways controlled by hydraulic structures in which the majority of flow is treated sewage effluent and there are periods of substantial combined sewer overflow. The Illinois Pollution Control Board (IPCB) designated the majority of the CWS as Secondary Contact and Indigenous Aquatic Life Use waters in the 1970s and made small alterations to these designations in 1988. Between 1988 and 2002 substantial improvements in the pollution control and water-quality management facilities were made in the Chicago area. The results of a Use Attainability Analysis led the Illinois Environmental Protection Agency (IEPA) to propose the division of the CWS into two new aquatic life use classes with appropriate dissolved oxygen (DO) standards. To aid the IPCB in their deliberations regarding the appropriate water use classifications and DO standards for the CWS, the DUFLOW model that is capable of simulating hydraulics and water-quality processes under unsteady-flow conditions was used to evaluate integrated strategies of water-quality improvement facilities that could meet the proposed DO standards during representative wet (2001) and dry (2003) years. A total of 28 new supplementary aeration stations with a maximum DO load of 80 or 100 g/s and aerated flow transfers at three locations in the CWS would be needed to achieve the IEPA proposed DO standards 100% of the time for both years. A much simpler and less costly (≈one tenth of the cost) system of facilities would be needed to meet the IEPA proposed DO standards 90% of the time. In theory, the combinations of flow augmentation and new supplemental aeration stations can achieve 100% compliance with the IEPA proposed DO standards, however, 100% compliance will be hard to achieve in practice because of—(1) difficulties in determining when to turn on the aeration stations and (2) localized heavy loads of pollutants during storms that may yield violations of the DO standards even with an extensive network of supplemental aeration stations. Thus, because absolute DO standards that must be met 100% of the time will be difficult, if not impossible to comply with, DO standards that include a Wet Weather Limited Use (WWLU) designation based on rainfall amount triggering CSO events and a maximum duration that the WWLU could be applied should be considered to obtain a healthy ecosystem by applying water-quality improvement features that can be practically operated and maintained. Such a WWLU approach also was evaluated in this paper.

Comparison of vertical-flow constructed wetlands with and without supplementary aeration treating decentralized domestic wastewater

Constructed wetlands (CWs) are efficient in reducing excessive contamination from wastewaters. However, oxygen inside CW beds is frequently low especially when substrate clogging problems appear after long-term operation, and this may become a limited factor for the treatment of wastewaters. Aimed at dealing with the issue of a low oxygen content in CW systems, two laboratory-scale vertical-flow constructed wetlands (VFCWs) with and without an aeration device (called VFCW-a and VFCW-c, respectively) were designed in this study to test the contribution of supplementary aeration to the treatment of decentralized domestic wastewater. Results showed that under the intermittent operation of about 45 days, two VFCW units were successfully started up by using activated sludge as seed sludge. Compared to VFCW-c, VFCW-a had a better resistance ability to organic shock loads and its removal function could be effectively recovered within a short period after the introduction of organic shock loads. Under intermittent operation with a 12 h idling time, the ideal hydraulic retention time (HRT) of VFCW-a was 42 h, about 6 h shorter than that of VFCW-c. Likewise, under intermittent operation with 42 h HRT, the ideal idling time of VFCW-a was 12 h, still about 6 h shorter than that of VFCW-c. Under intermittent operation with HRT-42 h and an idling time of 12 h, SS, COD, TN and TP removal efficiencies in VFCW-a could reach 81.2%, 85%, 89.9% and 77.9%, respectively. The VFCW unit with supplementary aeration is an efficient innovation for the treatment of decentralized domestic wastewater.

Saline water for juvenile giant trahira during feed training

The objective of this study was to investigate the effect of different water salinities on juvenile Hoplias lacerdae during feed training. Salinity levels of 0, 3, 6 and 9 g salt L-1 were used. Juveniles (3.33±0.1 cm and 0.6±0.09 g) were stocked at a density of six fish L-1 in aquaria (10 L volume) with supplementary aeration. Weight gain, length gain, and rates of survival, mortality, and cannibalism were evaluated after 20 days. Total mortality was observed in 0 g of salt L-1. The best survival rates of 98.7 and 97.5% were recorded in 3 and 6 g of salt L-1, respectively. The greatest weight gain was recorded in fish grown in 3 g of salt L-1 followed by fish grown in 6 g of salt L-1. Length gain was similar in the 3 and 6 g salt L-1 groups. No weight or length gain was recorded in 9 g of salt L-1. According to regression equations, the optimum water salinity was 5.15, 4.03 and 4.55 g of salt L-1 for survival rate, weight, and length gain, respectively. Salinity between 4.03 and 5.15 g of salt L-1 during feed training of juvenile giant trahira improves productive performance.

Nutrient removal in vertical subsurface flow constructed wetlands treating eutrophic river water

Four planted (Typha latifolia L.) pilot-scale vertical subsurface flow constructed wetlands were constructed to purify the eutrophic water of the Jinhe River in Tianjin (China) and to determine the feasibility of constructing a full-scale system in the future. The effects of intermittent artificial aeration and the use of polyhedron hollow polypropylene balls (PHPB) as part of the wetland substrate on the nutrient removal potential were also evaluated. During the entire running period, supplementary aeration enhanced the chemical oxygen demand, ammonia-nitrogen, total nitrogen, soluble reactive phosphorus and total phosphorus first order mean removal constants by 0.28 m/d, 3.05 m/d, 0.92 m/d, 0.74 m/d and 0.60 m/d, respectively, but reduced the nitrate-nitrogen removal constant by 1.72 m/d in contrast to non-aerated wetlands. A significantly positive contribution of PHPB to nutrient removal was obtained. The combination of artificial aeration and PHPB resulted in the augmentation of the first order mean removal constants by 0.29 m/d, 3.12 m/d, 1.15 m/d, 0.65 m/d and 0.54 m/d for chemical oxygen demand, ammonia-nitrogen, total nitrogen, soluble reactive phosphorus and total phosphorus, respectively. Findings from a brief cost-benefit analysis suggest that both artificial aeration and the presence of PHPB would result in enhanced nutrient removal that is cost efficient for future projects, particularly if electricity costs are low.

Allocation of supplementary aeration stations in the Chicago waterway system for dissolved oxygen improvement

The Chicago Waterway System (CWS), used mainly for commercial and recreational navigation and for urban drainage, is a 122.8 km branching network of navigable waterways controlled by hydraulic structures. The CWS receives pollutant loads from 3 of the largest wastewater treatment plants in the world, nearly 240 gravity Combined Sewer Overflows (CSO), 3 CSO pumping stations, direct diversions from Lake Michigan, and eleven tributary streams or drainage areas. Even though treatment plant effluent concentrations meet the applicable standards and most reaches of the CWS meet the applicable water quality standards, Dissolved Oxygen (DO) standards are not met in the CWS during some periods. A Use Attainability Analysis was initiated to evaluate what water quality standards can be achieved in the CWS. The UAA team identified several DO improvement alternatives including new supplementary aeration stations. Because of the dynamic nature of the CWS, the DUFLOW model that is capable of simulating hydraulics and water quality processes under unsteady-flow conditions was used to evaluate the effectiveness of new supplementary aeration stations. This paper details the use of the DUFLOW model to size and locate supplementary aeration stations. In order to determine the size and location of supplemental aeration stations, 90% compliance with a 5 mg/l DO standard was used as a planning target. The simulations showed that a total of four new supplementary aeration stations with oxygen supply capacities ranging from 30 to 80 g/s would be sufficient to meet the proposed target DO concentration for the North Branch and South Branch of the Chicago River. There are several aeration technologies, two of which are already being used in the CWS, available and the UAA team determined that the total capital costs of the alternatives range from $35.5 to $89.9 million with annual operations and maintenance costs ranging from $554,000 to $2.14 million. Supplemental aeration stations have been shown to be a potentially effective means to improve DO concentrations in the CWS and will be included in developing an integrated strategy for improving water quality in the CWS.

Treatment of azo dye Acid Orange 7 containing wastewater using up-flow constructed wetland with and without supplementary aeration

The aim of this study is to examine and compare the treatment performance of Acid Orange 7 (AO7) containing wastewater by up-flow constructed wetland (UFCW) at different AO7 concentrations, hydraulic retention times (HRT) and alternative of supplementary aeration. The aerated wetland reactor outperformed the non-aerated one in the removal of organic matters, NH(4)-N and aromatic amines. The T-P removal efficiency for both wetland reactors was not much different throughout the study and the supplementary aeration showed no significant effect on T-P removal. As influent AO7 concentration increased from 50 to 100 mg/L, the performance in biodegradation of organic matters and nitrification in the non-aerated wetland reactor, and denitrification and decolorization in the aerated wetland reactor were affected. As HRT increased from 3 to 6 d, the removal of NH(4)-N and NO(3)-N in the aerated wetland reactor was not significantly different, but the NH(4)-N removal efficiency improved tremendously in the non-aerated wetland reactor.

Performance evaluation of laboratory scale up-flow constructed wetlands with different designs and emergent plants

The objective of present study was to assess the simultaneous removal of organic pollutants and nutrients by five laboratory scale up-flow constructed wetlands (UFCWs). Aerobic and anaerobic regions were well developed at the upper and lower beds, respectively, in the UFCW reactors with supplementary aeration. The emergent plants employed were Phragmites australis and Manchurian wild rice. The COD, T–N, T–P, NH 4-N and NO 3-N removal efficiencies for the UFCW reactors were in the range of 90–94%, 69–92%, 29–52%, 59–98% and 45–100%, respectively. The organic matter and NH 4-N removal efficiencies in the aerated wetland reactors were better than the non-aerated wetland reactors. The supplementary aeration has enhanced the aerobic biodegradation of organic matter and nitrification. The Manchurian wild rice outperformed P. australis in the removals of T–P, T–N and NH 4-N.