Inflow Load Research Articles

Removal of monochlorobenzene and perchloroethene in wetland rhizosphere model systems

Constructed wetlands are a promising technology to protect river flood plains against the impact of contaminated groundwater. They are suitable for the treatment of waters contaminated with monochlorobenzene and perchloroethene. However, the removal performance differs with the operation conditions, and generally, transferable performance data are not yet available. In this study, removal efficiencies were determined and the dominant removal processes for monochlorobenzene and perchloroethene were evaluated under various operation conditions in helophyte rhizosphere reactors. Monochlorobenzene removal was very efficient (>99%) under low carbon load (overall oxic) and moderate carbon load (overall reduced) conditions. Higher loads of easily degradable carbon (acetate, 300 mg/L) impaired the elimination of monochlorobenzene (removal of 72−96%). Microbial reductive dechlorination of perchloroethene was not detected in the rhizosphere under low carbon load, sulphate reduction, and high-carbon load conditions. Nonetheless, considerable amounts of perchloroethene were eliminated (79−87%), presumably by plant uptake and phytovolatilisation. Under fluctuating moderate carbon load conditions, perchloroethene dechlorination was initiated, and trichloroethene and cis-dichloroethene production showed that a minimum of 10% of the perchloroethene inflow load was dechlorinated. Sulphate reduction and the associated sulphide toxicity showed to constitute a hazard for constructed wetland treatment of sulphate containing groundwater contaminated with chlorinated volatile organic compounds, causing a decrease in removal efficiencies by 50 and 20% for monochlorobenzene and perchloroethene, respectively.

Storm-Water Bioretention for Runoff Quality and Quantity Mitigation

In response to water quality and quantity issues within the Stroubles Creek watershed in Blacksburg, Virginia, a retrofit bioretention cell (BRC) was installed to collect and treat runoff from an existing parking lot. The BRC was completed in July 2007, and 28 precipitation events were monitored between October 2007 and June 2008. For each storm, inflow and outflow flow-weighted composite samples were collected and analyzed for suspended sediment, total nitrogen, and total phosphorus. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were analyzed to evaluate BRC efficiency. Overall, the BRC successfully reduced flow volumes and peak flow rates leaving the parking lot by 97 and 99%, respectively. Cumulative mass reductions for sediment, total nitrogen, and total phosphorus all exceeded 99% by mass. The findings of this study have significant implications for areas with karst geology: (1) current design recommendations of lining the bottom of ...

Adaptation of a Constructed Wetland to Simultaneous Treatment of Monochlorobenzene and Perchloroethene

Mixed groundwater contaminations by chlorinated volatile organic compounds (VOC) cause environmental hazards if contaminated groundwater discharges into surface waters and river floodplains. Constructed wetlands (CW) or engineered natural wetlands provide a promising technology for the protection of sensitive water bodies. We adapted a constructed wetland able to treat monochlorobenzene (MCB) contaminated groundwater to a mixture of MCB and tetrachloroethene (PCE), representing low and high chlorinated model VOC. Simultaneous treatment of both compounds was efficient after an adaptation time of 2½ years. Removal of MCB was temporarily impaired by PCE addition, but after adaptation a MCB concentration decrease of up to 64% (55.3 μmol L−1) was observed. Oxygen availability in the rhizosphere was relatively low, leading to sub-optimal MCB elimination but providing also appropriate conditions for PCE dechlorination. PCE and metabolites concentration patterns indicated a very slow system adaptation. However, under steady state conditions complete removal of PCE inflow concentrations of 10–15 μmol L−1 was achieved with negligible concentrations of chlorinated metabolites in the outflow. Recovery of total dechlorination metabolite loads corresponding to 100%, and ethene loads corresponding to 30% of the PCE inflow load provided evidence for complete reductive dechlorination, corroborated by the detection of Dehalococcoides sp.

Change of Inflow Load and Water Environment in Osaka Bay

To clarify change and actual condition of inflow load and sea environment in Osaka Bay from a not only quantitative but also qualitative point of view, loading amounts of COD, phosphorus, and nitrogen from 1980 to 2005 were estimated by collecting and analyzing statistical data about rivers, coastal waters, sewerage systems and so on. As a result, it was revealed that the plan outlined for reducing total pollution loads and the construction of sewerage system for years have shifted a nutrient balance of the inflow load and brought about changes in water quality structure and ecosystem in the bay. Moreover, analysis results indicated that nutrient loads caused by flood which people couldn't control had a significant impact on an annual total load compared with inflow loads in the ordinary condition.

Modelling sewer sediment deposition, erosion, and transport processes to predict acute influent and reduce combined sewer overflows and CO2 emissions

Understanding of solids deposition, erosion, and transport processes in sewer systems has improved considerably in the past decade. This has provided guidance for controlling sewer solids and associated acute pollutants to protect the environment and improve the operation of wastewater systems. Although measures to decrease combined sewer overflow (CSO) events have reduced the amount of discharged pollution, overflows continue to occur during rainy weather in combined sewer systems. The solution lies in the amount of water allotted to various processes in an effluent treatment system, in impact evaluation of water quality and prediction technology, and in stressing the importance of developing a control technology. Extremely contaminated inflow has been a serious research subject, especially in connection with the influence of rainy weather on nitrogen and organic matter removal efficiency in wastewater treatment plants (WWTP). An intensive investigation of an extremely polluted inflow load to WWTP during rainy weather was conducted in the city of Matsuyama, the region used for the present research on total suspended solid (TSS) concentration. Since the inflow during rainy weather can be as much as 400 times that in dry weather, almost all sewers are unsettled and overflowing when a rain event is more than moderate. Another concern is the energy consumed by wastewater treatment; this problem has become important from the viewpoint of reducing CO(2) emissions and overall costs. Therefore, while establishing a prediction technology for the inflow water quality characteristics of a sewage disposal plant is an important priority, the development of a management/control method for an effluent treatment system that minimises energy consumption and CO(2) emissions due to water disposal is also a pressing research topic with regards to the quality of treated water. The procedure to improve water quality must make use of not only water quality and biotic criteria, but also modelling systems to enable the user to link the effect of changes in urban sewage systems with specific quality, energy consumption, CO(2) emission, and ecological improvements of the receiving water.

Nutrient uptake and release in ponds under long-term and short-term lotus ( Nelumbo nucifera) cultivation: Influence of compost application

Uptake and release of nutrients from ponds used for lotus cultivation were measured in ponds under short-term (1 yr) cultivation with compost application (pond I) and under long-term (20 yr) cultivation without compost application (pond II). Total inflow loads of TN (irrigation water, rainfall and compost) during lotus cultivation period in ponds I and II were 72.3 and 34.3 kg ha −1 182 day −1, respectively. TN removal rates in ponds I and II were 77.3 and 49.8% of total inflow load, respectively. Major removal mechanisms of TN were attributed to microbial processes and uptake by lotus. The total outflow loads (infiltration and runoff) of TN during the lotus cultivation period were 13.9 kg ha −1 182 day −1 (19.2% of total inflow TN load) for pond I, and 11.3 kg ha −1 182 day −1 (32.9% of total inflow TN load) for pond II. For TP the total inflow loads (irrigation water, rainfall and compost) during lotus cultivation in ponds I and II were 80.8 and 1.9 kg ha −1 182 day −1, respectively. TP removal rates in ponds I and II were 84.9 and −274.1% of total input, respectively. Phosphorus removal was attributed to lotus uptake and soil adsorption. The total outflow loads (infiltration and runoff) of TP during lotus cultivation period were 10.1 kg ha −1 182 day −1 (12.5% of total inflow TP load) for pond I, and 6.6 kg ha −1 182 day −1 (355.6% of total inflow TP load) for pond II. TN and TP in runoff from pond I (with compost) was higher than that in pond II (without compost), showing that TN and TP in runoff were strongly influenced by compost addition. Therefore, in order to satisfy established water-quality standards, the amount of compost used in lotus cultivation should be evaluated.

Influence of Carbohydrate for Stabilization in Sediment at Ariake Sea Tideland and at Cikugo River Estuary

In the sediment of the estuary of the Chikugo River where inflow load quantity to Ariake Sea was bigger ,the carbohydrate was measured. The carbohydrate in the sediment surface of the estuary of the Chikugo River quantity was around 10 times higher than Ariake Sea sediment. Carbohydrate quantity to the time of edd tide is increased and to the times of a high-tide was decrease, it based on dissolubility carbohydrate caused by an adhesion alga. The dissolubility carbohydrates have chesion effect, and stabilization of sediment increased.

Removal of nitrogen in constructed wetlands with horizontal sub-sureface flow: a review

The paper describes the removal of nitrogen in horizontal sub-surface flow constructed wetlands (HF CWs) for various types of wastewater. The survey includes more than 900 annual means from more than 300 systems in 36 countries that were categorized into municipal, industrial, agricultural, and landfill leachate. The results revealed that the highest average concentration of total nitrogen (TN) was found in landfill leachate (211 mg l−1), while the highest average loading (3,080 g N m−2 yr−1) was recorded for systems treating wastewater from industrial operations. The average inflow TN concentration and loading for all systems were 63 mg l−1 and 1,158 g N m−2 yr−1, respectively. For ammonia-N the results were similar — the highest average inflow concentration (162 mg 1−1 was recorded for landfill leachate and the highest average loading was recorded for agricultural wastewaters (2,722 g N−2 yr−1). The results also indicated that there is a good relationship between inflow and outflow concentrations and loadings for both TN and NH4-N. Harvesting aboveground biomass of emergent macrophytes in HF CWs removes only limited amount of nitrogen as compared to inflow load (commonly <10%).

Influence of Dynamic Stall and Dynamic Wake Effects on Helicopter Trim and Rotor Loads

Flight test data of helicopters indicate that vibratory levels in the fuselage exhibit a wide spectrum of frequencies including the dominant blade passage frequency and its integer multiples. The present work attempts to understand the reason for the existence of several frequencies in the response of the fuselage and possible cause for this observed phenomenon by formulating a computational aeroelastic model. In this theoretical study, a systematic approach has been undertaken to identify the effects of inflow modeling and sectional aerodynamic load evaluation, on helicopter trim, rotor blade response, and hub loads. Five different combinations of aerodynamic models of increasing complexity, representing rotor inflow and sectional aerodynamic loads, have been proposed. The differential equations of motion are solved in time domain in a sequential manner to obtain the response of all the blades in the rotor system, the inflow variables, and the sectional loads at every time step. The results of the present study show that the aerodynamic model incorporating dynamic wake and dynamic stall effects introduces a wide spectrum of harmonics in the hub loads including blade passage frequency and its integer multiples. The influence of aerodynamic modeling on the variation of trim parameters with forward speed has also been brought out. It is observed that the aerodynamic model incorporating dynamic wake and dynamic stall effects predicts the trim parameters whose variation with forward speed resemble qualitatively similar to those obtained in flight test. A comparison of the variation of blade sectional lift for various aerodynamic models indicates that in the advancing side of the rotor, a dynamic stall model introduces a shift in the azimuth angle at which the minimum lift occurs. The effect of structural flap—lag coupling due to blade pretwist on trim and rotor loads has been studied, and these results are compared with those pertaining to a straight blade configuration. ©2009 American Helicopter Society

Phosphorus removal from agricultural runoff by constructed wetland

A free-water surface wetland covering an area of 2800 m 2 was operated from March 2002 to June 2004 for agricultural runoff treatment in the Dianchi Valley in China. In the wetland were grown Zizania Caduciflora Turez Hand-mazt and Phragmites australis ( Cav.) Trin.ex Steud. The instantaneous inflow rate was measured and the integrated flux was recorded by an ultrasonic flow instrument all year round. The average inflow rate, hydraulic loading rate (HLR) and hydraulic retention time (HRT) were kept at 242 m 3 d −1, 12.7 cm d −1 and 2.0 d, respectively. The annual average total phosphorus (TP) in the inflow was 0.87 mg L −1, and the corresponding removal efficiency was calculated to be 59.0%. Biannual plant uptake and removal by harvesting and seed transport was the main pathway for TP removal, while the influent TP load was 12.9 g m −2 year −1. Hydraulic retention time had a significant positive correlation with the removal of P ( r 2 = 0.88). Water temperature, inflow phosphorus load, inflow and hydraulic load rates were positively correlated with the removal of P. Inflow phosphorus concentrations were negatively correlated with the removal of P. It is shown that the free-water surface wetland was an effective and economical system for agricultural runoff treatment in lake regions.

Nitrogen removal from agricultural runoff by full-scale constructed wetland in China

We aimed at indicating some regularities of a constructed wetland treating agricultural runoff in China. The regularities, including the nitrogen removal capacity all year round, the nitrogen distribution pathways, and the nitrogen species removal kinetics, of a free water surface constructed wetland (2,800 m2) in the Dianchi Valley, which has been in operation for 27 months, were studied. The planted Phragmites australis and Zizania caduciflora were harvested biannually. The average inflow rate was recorded by an ultrasonic flow instrument, and then the hydraulic loading rate (HLR) and hydraulic retention time (HRT) were calculated. The average inflow and outflow concentrations of total nitrogen (TN), ammonia, and nitrate were measured, while the corresponding removal rates were calculated, showing better results than other constructed wetlands. Then the distribution pathways of nitrogen were analyzed, which indicated that plant harvesting was more important in wetland-treated agricultural runoff than in domestic wastewater. The reason for a good nitrogen removal capability and the obvious function of plants in the present wetland is the sound climate and intermittent inflow in the wetland. Results showed that inflow load had significant correction with both TN and ammonia removal efficiency. HLR, inflow rate, inflow nitrogen concentration, and temperature had significant and positive correction with both TN and ammonia removal. However, HRT had negative correction with both TN and ammonia removal, and the nitrate removal efficiency and parameters mentioned earlier were not significantly correlated. The rate constant values for nitrate and ammonia in summer were obviously larger than in winter. It is possible that bacterial and microbial activities were more active in summer than winter, and more conducive to bacterial and vegetative growth in summer than winter. Since this study was a pioneer for the implementation of constructed wetlands in China treating agricultural runoff, it has proved that this eco-technology could be used effectively for water quality enhancement in China and other areas with a similar climate.

Circulating fluidized bed biological reactor for nutrients removal

A new biological nitrogen removal process, which is named herein “The circulating fluidized bed bioreactor (CFBBR)”, was developed for simultaneous removal of nitrogen and organic matter. This process was composed of an anaerobic bed (Riser), aerobic bed (Downer) and connecting device. Influent and nitrified liquid from the aerobic bed enters the anaerobic bed from the bottom of the anaerobic bed, completing the removal of nitrogen and organic matter. The system performance under the conditions of different inflow loadings and nitrified liquid recirculation rates ranging from 200% to 600% was examined. From a technical and economic point of view, the optimum nitrified liquid recirculation ratewas 400%. With a shortest total retention time of 2.5 h (0.8 h in the anaerobic bed and 1.5 h in the aerobic bed) and a nitrified liquid recirculation rate of 400% based on the influent flow rate, the average removal efficiencies of total nitrogen (TN) and soluble chemical oxygen demand (SCOD) were found to be 88% and 95%, respectively. The average effluent concentrations of TN and SCOD were 3.5 mg/L and 16 mg/L, respectively. The volatile suspended solid (VSS) concentration, nitrification rate and denitrification rate in the system were less than 1.0 g/L, 0.026-0.1 g NH4+-N/g VSS·d, and 0.016–0.074 g NOx−-N/g VSS·d, respectively.

Nitrogen and phosphorus standing stock in Phalaris arundinacea and Phragmites australis in a constructed treatment wetland: 3-year study

Constructed wetland with sub-surface horizontal flow at Břehov near České Budějovice, Czech Republic is designed to treat sewage from 100 population equivalent. The system was put into operation in late 2003 and it consists of two rectangular beds (28 (L) × 9 (W) m each) planted with Reed canarygrass (Phalaris arundinacea) and Common reed (Phragmites australis) in bands parallel to the flow. Aboveground biomass of Phalaris and Phragmites was harvested in 2004, 2005 and 2006 during the peak standing crop of both species, i.e. in July for Phalaris and the early September for Phragmites. In 2004 and 2005, also belowground biomass was harvested. The major objective of the study was to evaluate the amount of nutrients sequestered in plant biomass and compare it with inflow loading. The analysis of the biomass indicated that the concentrations of nitrogen and phosphorus in various parts of both species were comparable in all three years. However, due to the higher biomass in 2005 and 2006 the nutrient standing stocks increased between 2004 and 2006 indicating that the most important factor for standing stock is the plant biomass. The results revealed that the amount of nutrients sequestered in the aboveground biomass and hence available for harvesting was low as compared to inflow load.

Assessment of the reliability of an on-site MBR system for greywater treatment and the associated aesthetic and health risks

This study analyses the reliability of an on-site MBR system for greywater treatment and reuse. To achieve this goal simulation was performed based on the IWA ASM1 model which was adapted to describe biological and physical mechanisms for MBR greywater treatment based systems. Model results were found to agree well with experimental data from an on site pilot greywater treatment plant, after which the calibrated model was used in a Monte Carlo mode for generating statistical data on the MBR system performance under different scenarios of failures and inflow loads variations. Effluents quality and their associated risks were successfully estimated.

Relationships between loading rates and nitrogen removal effectiveness in subsurface flow constructed wetlands

Nitrogen removal of wetlands under 40 different inflow loadings were studied in the field during 15 months. The removal efficiency of four different sets of beds, namely the reed bed, the Zizania caduciflor bed, the mixing planting bed, and the control bed were studied. The outflow loading and total nitrogen (TN) removal rate of these beds under different inflow loadings and pollution loadings were investigated. The inflow loadings of 4 subsurface flow systems (SFS) ranged from 400 to 8000 mg·(m2·d)−1, while outflow loadings were less than 7000 mg·(m2·d)−1. The results showed that the inflow and outflow loading of TN removal rate in SFS presented an obvious linear relationship. The optical inflow loading to run the system was between 2000 to 4000 mg·(m2·d)−1. Average removal rate was between 1062 and 2007 mg·(m2·d)−1. SFS with plant had a better removal rate than the control. TN removal rates of the reed and Zizania caduciflora bed were 63% and 27% higher than the control bed, respectively. The results regarding the TN absorption of plants indicated that the absorption amount was very limited, less than 5% of the total removal. It proved that plants clearly increase TN removal rates by improving the water flow, and increasing the biomass, as well as activities of microorganisms around the roots. The research provided a perspective for understanding the TN removal mechanism and design for SFS.

IMPACT ANALYSIS OF RAINFALL ON WATER QUALITY AND PRIMARY PRODUCTION IN THE OSAKA BAY

Water quality and primary production in an enclosed bay are dependent on inflow loads from rivers and outer ocean, and nutrients released from sea bottom. A nutrient load by rainfall also has an important role in the primary production. We here focused on the influence of the precipitation on the water quality and primary production in the Osaka Bay, and then conducted water quality analyses of rainwater and river water.The rainwater had high concentration of dissolved inorganic nitrogen, and the ratio of rainfall load to Yodo River load was about 20% on average for observation period. This result suggests that the precipitation make phytoplankton biomass increase in the surface layer with nitrogen limitation. Furthermore we examined the changes of water quality and primary production using a system dynamics model to make a quantitatively evaluation of precipitation effect.

Water Quality of Rainwater and Its Impact on Primary Production in the Osaka Bay

A nutrient load by rainfall has an important role in the primary production in an enclosed bay. We made analyses of rainwater qualities around the Osaka Bay, and calculations for the impact of the precipitation on the water quality and primary production in the Osaka Bay, using a 3D hydrodynamic water-quality model. The rainwater had high concentration of T-N about 0.7mg/L on average for observed rains. The total precipitation loads of T-N, T-P were 1, 300, 11 ton/year, which are only about 3% and 0.4% of total inflow load in the Osaka Bay, respectively. However, calculation results show that the precipitation make phytoplankton biomass increase in the surface layer about 3μg/L in the southwest area of the bay, where the tidal exchange is small and the DIN concentration is very low.

Attempt on Permissible Inflow Load of COD in Enclosed Coastal Seas

Attempt on Permissible Inflow Load of COD in Enclosed Coastal Seas

Modelling the energy balance of an anaerobic digester fed with cattle manure and renewable energy crops

Knowledge of the net energy production of anaerobic fermenters is important for reliable modelling of the efficiency of anaerobic digestion processes. By using the Anaerobic Digestion Model No. 1 (ADM1) the simulation of biogas production and composition is possible. This paper shows the application and modification of ADM1 to simulate energy production of the digestion of cattle manure and renewable energy crops. The paper additionally presents an energy balance model, which enables the dynamic calculation of the net energy production. The model was applied to a pilot-scale biogas reactor. It was found in a simulation study that a continuous feeding and splitting of the reactor feed into smaller heaps do not generally have a positive effect on the net energy yield. The simulation study showed that the ratio of co-substrate to liquid manure in the inflow determines the net energy production when the inflow load is split into smaller heaps. Mathematical equations are presented to calculate the increase of biogas and methane yield for the digestion of liquid manure and lipids for different feeding intervals. Calculations of different kinds of energy losses for the pilot-scale digester showed high dynamic variations, demonstrating the significance of using a dynamic energy balance model.

Evaluation of pollutant removal in a constructed irrigation pond

A year-long study on the water quality and hydrology was carried out to investigate the characteristics of the pollutant concentrations and pollutant removal in a constructed irrigation pond. The pond is part of a circular irrigation system for paddy fields within Lake Kasumigaura watershed, Japan. The average concentrations of the total nitrogen (TN), chemical oxygen demand (COD), total phosphorus (TP), and suspended solids (SS) at the pond outlet were 7.4, 8.6, 0.2, and 18.8 mg L−1, respectively. The average removed loads for the same indices were 0.14, 2.47, 0.11, and 24.2 g m−2 day−1, respectively. The percentages of pollutant removals from the inflow loads for the same indices were 3, 26, 42, and 63%, respectively. The pond discharged the TN loads of 128 kg due to sediments stirred by operation of a pump for April and May. The average TN removal was 19% from June to August and was smaller than that reported in published literatures (40–50%). Major reasons were considered to be that the turnover of water in the pond was rapid (86% per day) and that the TN concentration of inflow water was relatively low (5.9 mg L−1). The percentages of pollutants that flowed into the pond to the outflow loads from the study site were 6.6, 4.8, 1.6, and 1.1% for TN, COD, TP, and SS loads, respectively. The pollutant removal will be increased if the design of the circular irrigation system is reconsidered to utilize a pollutant removal function in the irrigation pond.