Sung-Ryong Ha

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

Lignite based granular activated carbon of 20×30 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.

Competitive Removal of Phenol and 2,4-Dichlorophenol in Biological Activated Carbon System

Laboratory scale experiments were conducted to evaluate the removal capacities of the major competitive components in a biological activated carbon (BAC) system. Adsorption, desorption, biodegradation, biosorption, and bioregeneration were considered as the major target reactions. Phenol and 2,4-dichlorophenol were used in a single and bisolute system. The adsorption experiment showed that 2,4-DCP was a stronger adsorbate than phenol both in single and bisolute systems. On desorption of 2,4-DCP, the small fraction of sorbed compounds was reversible but phenol had comparatively high reversibility. All solutions exhibited high degrees of irreversible adsorption as hysteresis. Desorption in background organics showed high reversibility. The biomass sorptions of phenol and 2,4-DCP were both negligible so that the removal of these compounds could be disregarded in the BAC system. Meanwhile, the biodegradation of phenol was higher than that of 2,4-DCP in both as a single and bisolute systems. The biodegradation of phenol was higher than that of 2,4-DCP in both single and bisolute systems. Although, the biodegradation capability of phenol was suppressed in the presence of 2,4-DCP but it induced the biodegradation of 2,4-DCP. In single solute, the degree of bioregeneration in terms of phenol and 2,4-DCP in single solute were 76.28% and 56.80%, respectively. In bisolute system, they were 74.46% and 60.20% for phenol and 2,4-DCP, respectively and degree of bioregeneration was corresponding to degree of hysteresis.

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

This study was undertaken to analyze the quantitative impact ofa municipal wastewater treatment operation on the long-term waterquality changes in a tributary of the Han-river, Korea from 1994to 1999. Changes of land use pattern in the study watershed arequantitatively analyzed on the basis of land use maps that werecreated by classifying Landsat TM images acquired in April 1994and March 1999. During this period, the average increase of landuse 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 averagereductions of BOD, T-N, and T-P by the municipal wastewatertreatment operation were about 89, 11 and 27%, respectively.Spatial analysis of the pollution discharge from watershed wasundertaken 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 studyperiod, water quality change in terms of BOD, T-N, and T-P were(+)1.04 mg l-1 (corresponding to a 13.7% increase ofpollution), (+)0.58 mg l-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 duringthe same period was about 67.6, 39, and 36.5%, respectively.Consequently, it is understood that total stream water qualityrecovery in terms of BOD, T-N, and T-P were 81.3, 49.0, and38.1% respectively, and that this included a negativecontribution resulting from increased land use and a positivecontribution due to the wastewater treatment operation atInchon.

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.

Probability mass first flush evaluation for combined sewer discharges.

The Korea government has put in a lot of effort to construct sanitation facilities for controlling non-point source pollution. The first flush phenomenon is a prime example of such pollution. However, to date, several serious problems have arisen in the operation and treatment effectiveness of these facilities due to unsuitable design flow volumes and pollution loads. It is difficult to assess the optimal flow volume and pollution mass when considering both monetary and temporal limitations. The objective of this article was to characterize the discharge of storm runoff pollution from urban catchments in Korea and to estimate the probability of mass first flush (MFFn) using the storm water management model and probability density functions. As a result of the review of gauged storms for the representative using probability density function with rainfall volumes during the last two years, all the gauged storms were found to be valid representative precipitation. Both the observed MFFn and probability MFFn in BE-1 denoted similarly large magnitudes of first flush with roughly 40% of the total pollution mass contained in the first 20% of the runoff. In the case of BE-2, however, there were significant difference between the observed MFFn and probability MFFn.

An Analysis on Inundation Characteristics of Urban Watershed according to Variation in Return Period of Design Rainfall

Abstract This study aims to investigate inundation characteristics such as inundated area, inundation depth according to variation in return period of design rainfall and to draw a comparison between the inundation characteristics by adapting design storm using dual-drainage model. Lidar data is used to construct terrain data with 1m × 1m resolution in Cheongju. The designed storm by return periods(10year, 30year, 50year and 200year) are acquired from Intensity Duration Frequency curve, which are distributed in 5 minutes interval using Huff’s method. As a results, the inundation volume is linearly increased, but inundated area is gradually increased in accordance with swell of return period for design storm. On the other hands, as a result of calculating discharge capacity for each points, deficit of discharge capacity is not observed using designed storm of 10 year return period at every points. If the return period is increased up more than 10 years, both the deficit of discharge capacity for each PT and entire study area are enlarged drastically.

Evaluation of the causes of inundation in a repeatedly flooded zone in the city of Cheongju, Korea, using a 1D/2D model

Currently, unprecedented levels of damage arising from major weather events have been experienced in a number of major cities worldwide. Furthermore, the frequency and the scale of these disasters appear to be increasing and this is viewed by some as tangible proof of climate change. In the urbanized areas sewer overflows and resulting inundation are attributed to the conversion of previous surfaces into impervious surfaces, resulting in increased volumes of runoff which exceed the capacity of sewer systems and in particular combined sewer systems. In this study, the characteristics of sewer overflows and inundation have been analyzed in a repeatedly flooded zone in the city of Cheongju in Korea. This included an assessment of inundation in a 50-year storm event with total rainfall of 165 mm. A detailed XP-SWMM 2D model was assembled and run to simulate the interaction of the sewage system overflows and surface inundation to determine if inundation is due to hydraulic capacity limitations in the sewers or limitations in surface inlet capacities or a combination of both. Calibration was undertaken using observation at three locations (PT #1, PT #2, PT #3) within the study area. In the case of the subsurface flow calibration, R(2) value of 0.91 and 0.78 respectively were achieved at PT #1 and PT #2. Extremely good agreement between observed and predicted surface flow depths was achieved also at PT #1 and PT #2. However, at PT #3 the predicted flow depth was 4 cm lower than the observed depth, which was attributed to the impact of buildings on the local flow distribution. Areas subject to flooding were classified as either Type A (due to insufficient hydraulic capacity of a sewer), Type B (which is an area without flooding notwithstanding insufficient hydraulic capacity of a sewer) or Type C (due to inlet limitations, i.e. there is hydraulic capacity in a sewer which is not utilized). In the total flooded zone, 24% was classified as Type A (10.2 ha) and 25% was classified as Type C (2.61 ha). It was concluded that greater attention should be paid to the area classified as Type B, which covers 50.5% (5.15 ha) of the total flooded zone.

An Evaluation of Solid Removal Efficiency in Coagulation System for Treating Combined Sewer Overflows by Return Sludge

In this study, the sludge that occurs in the initial operation of coagulation system developed for the treatment of CSOs were returned to the flocculation reactor. The purposes of this study were to analyze the Characteristics of flocs that are generated through the recycling sludge and settling characteristics of sludge, and to evaluate the possibility that high concentrations of particulate matter in the initial inflow of CSOs could be used as an weighted coagulant additive. As a result, the concentration of treated CSOs pollutants at the beginning of the CSOs influent with a large amount of particulate matter over 20 was low, after gradually increasing the concentrations of them. The flocs generated from the sludge return were similar in size compared to flocs generated through injection of micro sands, and settling velocity in case of return sludge injection was decreased from 55.1 cm/min to 21.5 cm/min. SVI value of the sludge accumulated at the bottom of the sedimentation tank was 72, and settled sludge volume decreased rapidly due to the consolidation of sludge to the time it takes to 10 minutes. these mean that sludge used for recycling has good settling characteristic. A condition of returned sludge which is 0.1% return of 0.3% extraction was formed in the balance of settlement and extraction. In this case, This condition was to be adequate to maintain the proper concentration such as 100~200 mg/L of TS and 50~100 mg/L of VS in the flocculation reactor. The usage of the return sludge containing particulate matters of CSOs as an weighted coagulant additive was able to secure a stable treated water quality despite the change of influent water quality dynamically. Furthermore, it can be expected to reduce the alum dosage along with the sludge production.

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.

Evaluation of Pilot scale Coagulation system Design for CSOs treatment

A pilot scale coagulation system, which has a function of physicochemical treatment, was developed to treat Combined sewer overflows(CSOs). This coagulation system requires evaluation of optimum design factors whether it has reflected those of lab scale system, moreover, the pilot scale system can be evaluated differently according to the characteristics of influent CSOs even though it has reflected lab scale`s design factors. We conducted an experiment using lab scale system that could treat of CSOs in a day, and also pilot-scale system with CSOs flowed into the Cheongju sewage treatment plant. Therefore the aim of this study is to evaluate a hydraulic similarity between the design factors of pilot scale and those of lab scale coagulation system, and to evaluate feasibility of the coagulation system for the CSOs treatment with optimum operation conditions. From the result of pilot-test, we drew the optimum operation factors of in line mixer and flocculator having similarities with those of lab scale system as well as the optimum coagulant dose. Finally we confirmed that the coagulation system has feasibility to treat the CSOs with high removal efficiency.