Characteristics of DOC concentration with storm density flows in a stratified dam reservoir.

Among natural organic matter (NOM) defined as the complex matrix of organic materials abundant in natural waters, a gradual accumulation of recalcitrant organic matter (ROM) has been observed in impounded water bodies such as a lake or dam reservoir in spite of extensive efforts made to curtail organic pollutant loadings generated in their catchment areas. This paper aims to identify the effect of diffuse pollution resulting from allochthonous organic matters on the temporal and spatial characteristics of organic matters in a stratified dam reservoir, Daecheong Dam, using both intensive observation and CE-QUAL-W2 model simulation. With the limitation of observation data in terms of organic matters of inflow waters from boundary tributaries and impounded water in the reservoir, organic matter was represented by organic carbon including labile particular organic carbon (LPOC), refractory organic carbon (RPOC), labile dissolved organic carbon (LDOC), and refractory organic carbon (RDOC). Both autochthonous and allochthonous origins of organic carbon were considered in the modeling of eutrophication of the reservoir water using CE-QUAL-W2. The result of simulation during the period from 2001 to 2005 was observed to be a gradual accumulation of particular organic carbon (POC). It is clear that the model calculation results enable the explanation of the internal and external movement of constituents in the reservoir. In particular turbidity and NOM were well related in the upper region of the reservoir according to flow distance, gradually changing to dissolved form of organic matter, DOC affected organic matter concentration of reservoir water quality compared to turbidity.

Nonlinear regression approach to evaluate nutrient delivery coefficient.

Implementation of the Korean Total Maximum Daily Load Act calls for new tools to quantify nutrient losses from diffuse sources at a river basin district scale. In this study, it was elucidated that the nonlinear regression model (NRM) reduces the uncertainty of the boundary conditions of the water quality model. The NRM was proposed to analyse the delivery coefficients of surface waters and retention coefficients of pollutants. Delivery coefficient of pollution load was considered as a function of two variables: the watershed form ratio, S(f), which is a measurable geomorphologic variable and the retention coefficient, phi, which is an empirical constant representing the basin-wide retarding capacity of pollutant wash-off. This model was applied on the Geum River, one of the major basins in South Korea. The QUAL2E was used to simulate stream water quality using NRM. In this paper, we elucidate the possibility to use a nonlinear regression model for delivery and retention of nutrients in a drainage basin characterized as both data-rich and data-poor, and the magnitude of the nutrient loads and sources has been uncertain for a long time.

GIS-based influence analysis of geomorphological properties on pollutant wash-off in agricultural area.

This study improves the estimation of the self-purification coefficient for runoff analysis of pollution load using geomorphological factors. Formerly, the assimilative capacity, K, was estimated using a single geomorphological factor, Horton's form ratio, St. Here, K was divided into two factors, namely, a watershed self-purification coefficient (K) and a watershed form ratio (S(f)). The watershed form ratio, S(f), is the equivalent stream density and is considered an index of accessibility of the pollution load to the water body. Even though Sf had shown a clear reciprocal relationship with K, in agricultural areas, there is a limitation that the K, estimated by using an S(f) only can't reflect the variability of land coverage characteristics and/or land use. In this study, a new geo-characteristic index (GCI), S(R), which is composed of Sf and weighted flow accumulation ratio (F(r)), is suggested. GIS and remote sensing technique were used to calculate S(f) and F(r). Interestingly, a clear reciprocal relationship exists between K and S(R), and this relationship seems to be stronger for agricultural areas, as urbanized areas have easier wash off due to the sewer network or paved surfaces.

Water quality management planning zone development by introducing a GIS tool in Kathmandu valley, Nepal.

This research was conducted to identify the critical pollution (BOD, TN, TP) areas and to develop the priority mitigation zone for the Bagmati River pollution in the Kathmandu valley, Nepal. A GIS tool was used to define and identify the critical pollution areas and sources. Pollution source information such as population, livestock, industry and land use were collected on the basis of the individual village boundary. The industrial, land use and living pollution were aggregated by the GIS overlay analysis capability to obtain the combined pollution load within the watershed. Priority areas for the mitigation of the pollution were defined considering the pollution loading rate, distance of stream from pollution source, and political, religious, and touristic values of the area. This research noticed that Kathmandu, Lalitpur and Bhaktapur municipalities are the major polluting areas and living beings are the major factors of Bagmati River pollution. Delivery ratio for the watershed was found to vary from 40-69% for BOD and nitrogen but the delivery of phosphorus was exceptionally high (92% at Gaurighat and 77% at Chovar) due to cremation activity of the Hindu religion on the riverbanks. Thus, the priority areas for the mitigation of the carbonaceous and nutrient source pollution were identified. At present the land use and industry impaired a very low contribution compared to the huge pollution load from the municipalities to the river system.

Impacts of agrochemical fertilizer on the aquatic environment of paddy fields in Vietnam.

To evaluate the impacts of agrochemical fertilizer application on the aquatic environment of paddy fields in tropical regions, 7.04 ha of paddy field situated in northern Vietnam were selected as a study area. The fate of nutrient constituents was surveyed through a questionnaire as well as analytical observation. Taking the major environmental components of the paddy field into account, a mass-balance flow regarding fertilizing constituents such as nitrogen and phosphate was built up and used to estimate the contribution of fertilizer to paddy field water pollution. In the mass-flow analysis, the randomness of fertilizer used by local farmers is incorporated within the conventional input-output model. For the control volume of soil in 0-40 cm below paddy plot surface, the estimated average concentrations in soil were 1.8 ppm for inorganic nitrogen and 1.3 ppm for inorganic phosphate on the assumption of 50% non-excessive probability. From the reasonable consistency of the deduced concentrations of nutrients with observed ones, not only the mass balance of fertilizing substances but also the impacts of fertilizer on the paddy field aquatic environment in Vietnam could be understood. On the results from nutrient mass-balance analysis, it was found that 11.3-13.3 kg N/ha would percolate into the underground aquifer that is linked to surface channel flow in the vicinity of the paddy plots and affect the irrigation water quality. The nutrient portion in the materials harvested as grain and straw occupied 58% of total dosed nitrogen and 75.6% of total supplied phosphorous.

Estimation of urban runoff and water quality using remote sensing and artificial intelligence.

Water quality and quantity of runoff are strongly dependent on the landuse and landcover (LULC) criteria. In this study, we developed a more improved parameter estimation procedure for the environmental model using remote sensing (RS) and artificial intelligence (AI) techniques. Landsat TM multi-band (7bands) and Korea Multi-Purpose Satellite (KOMPSAT) panchromatic data were selected for input data processing. We employed two kinds of artificial intelligence techniques, RBF-NN (radial-basis-function neural network) and ANN (artificial neural network), to classify LULC of the study area. A bootstrap resampling method, a statistical technique, was employed to generate the confidence intervals and distribution of the unit load. SWMM was used to simulate the urban runoff and water quality and applied to the study watershed. The condition of urban flow and non-point contaminations was simulated with rainfall-runoff and measured water quality data. The estimated total runoff, peak time, and pollutant generation varied considerably according to the classification accuracy and percentile unit load applied. The proposed procedure would efficiently be applied to water quality and runoff simulation in a rapidly changing urban area.

Improvement of pre- and post-processing environments of the dynamic two-dimensional reservoir model CE-QUAL-W2 based on GIS.

An Environmental Information System (EIS) coupled with a Geographic Information System (GIS) and water quality models is developed to improve the pre- and post-data processing function of CE-QUAL-W2. Since the accuracy of the geometric data in terms of a diverse water body has a great effect on the water quality variables such as the velocity, kinetic reactions, the horizontal and vertical momentum, to prepare the bathymetry information has been considered a difficult issue for modellers who intend to use the model. For identifying Cross Section and Profile Information (CSPI), which precisely contains hydraulic features and geographical configuration of a waterway, the automated CSPI extraction program has been developed using Avenue Language of the PC Arc/view package. The program consists of three major steps: (1) getting the digital depth map of a waterway using GIS techniques; (2) creating a CSPI data set of segments in each branch using the program for CE-QUAL-W2 bathymetry input; (3) selecting the optimal set of bathymetry input by which the calculated water volume meets the observed volume of the water body. Through those approaches, it is clear that the model simulation results in terms of water quality as well as reservoir hydraulics rely upon the accuracy of bathymetry information.

Catalytic wet air oxidation of p-nitrophenol (PNP) aqueous solution using multi-component heterogeneous catalysts.

This study investigated the decomposition of high strength p-nitrophenol (PNP) of 2,000 mg/l (3,400 mg of COD/1,250 mg of TOC) by catalytic wet air oxidation. Multi-component heterogeneous catalysts were used as catalysts for this purpose. The study results using a batch reactor showed that catalyst "D" (Mn-Ce-Zr 22.4 g plus CuSO4 1.0 g; Mn-Ce-Zr-Cu [CuSO4]) was more effective (56-74%) than catalyst "A" (Mn-Ce-Zr 22.4 g) under the given conditions (O2 partial pressure of 1.0 MPa; temperature of 170-190 degrees C; 30 min of reaction time). The best result was obtained when 2 g of Mn-Ce-Zr-Cu [CuSO4] was used per 1L of PNP aqueous solution. COD and TOC removal efficiencies were 18% and 23% without catalysts during 20 min of reaction at 190 degrees C. They were improved to 79% and 71% with 2 g/L of Mn-Ce-Zr-Cu [CuSO4] under the same conditions. The ratio of BOD5/COD was measured to evaluate biodegradability. It was 0.05 without catalyst and increased to 0.33 with 2 g/L of Mn-Ce-Zr-Cu [CuSO4] for 20 min of reaction.

Quantitative bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol.

Lignite based granular activated carbon of 20x30 mesh size was used to investigate the extent of bioregeneration of phenol and 2,4-DCP in a batch system. The adsorption isotherm fits very well with the Freundlich isotherm and it is apparent that 2,4-DCP is more adsorbable than phenol. The degree of reversible adsorption for phenol and 2,4-DCP were 32.9 and 10.6 %, respectively. The low percentages of their reversibility meant that the adsorption phenomena of both phenol and 2,4-DCP were not fully physicosorption. The microorganisms can regenerate 31.4% (21.2 mg g(-1)) of GAC loaded with phenol and 14.3% (24.8 mg g(-1)) of GAC loaded with 2,4-DCP over a period of 7-10 days. The bioregeneration of phenols closely followed the first order kinetics with the rate constant of 0.046 day(-1) at initial phenol concentration of 100 mg l(-1) and biomass concentration of 20 mg l(-1) MLVSS. The rate constant was 0.021 day(-1) at initial 2,4-DCP concentration of 200 mg l(-1) and 200 mg l(-1) MLVSS. In addition, the increasing in initial concentration of biomass in the solution shortened the time required to reach the asymptotic limit on the bioregeneration but rendered little impact on the bioregeneration percentage.

Effects of land use and municipal wastewater treatment changes on stream water quality.

This study was undertaken to analyze the quantitative impact of a municipal wastewater treatment operation on the long-term water quality changes in a tributary of the Han-river, Korea from 1994 to 1999. Changes of land use pattern in the study watershed are quantitatively analyzed on the basis of land use maps that were created by classifying Landsat TM images acquired in April 1994 and March 1999. During this period, the average increase of land use area in terms of residence, cultivation, and barren was 5.89, 0.13, and 0.12%, respectively, and the corresponding decrease in water and forest area was 0.21 and 0.16%. The annual average reductions of BOD, T-N, and T-P by the municipal wastewater treatment operation were about 89, 11 and 27%, respectively. Spatial analysis of the pollution discharge from watershed was undertaken using a geographic information system (GIS) based model. A clear reciprocal relationship was found between the basin-wide self-purification coefficient and the watershed form ratio excepting a catchment area with water drain facilities. Due to land use changes over the five year study period, water quality change in terms of BOD, T-N, and T-P were (+)1.04 mg l(-1) (corresponding to a 13.7% increase of pollution), (+)0.58 mgl(-1) (10.0% increase), and (-)0.01 mg l(-1) (1.6% decrease). On the other hand, the effect of water quality restoration assessed by outward appearance during the same period was about 67.6, 39, and 36.5%, respectively. Consequently, it is understood that total stream water quality recovery in terms of BOD, T-N, and T-P were 81.3, 49.0, and 38.1% respectively, and that this included a negative contribution resulting from increased land use and a positive contribution due to the wastewater treatment operation at Inchon.

A modeling approach to bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol.

A predictive isotherm model was developed to evaluate the extent of bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol (2,4-DCP). Two basic substrates (116 mg/L of phenol and 100 g/L 2,4-DCP) as single solute were prepared. The mixture of them was provided to bisolute system for assessing the competitive adsorption. The effect of by-products, which were generated during biodegradation of substrate and measured as COD, on bioregeneration in the bisolute was investigated. Freundlich adsorption parameters (Kads and 1/n) of 2,4-DCP were obviously higher than those of phenol in both single and bisolute. By-products in the bulk solution brought an adverse effect on adsorption capacity of GAC in all cases. By taking into account the by-product effect on adsorption, the Freundlich isotherms were used to formulate a predictive model of bioregeneration. Simulated results showed good consistency of observed results. Practical relevant of the proposed model for assessing of bioregeneration in the wastewater treatment was discussed by applying model to the BAC-SBR in the steady-state operation.