Phosphorus (P) removal by aluminum sulfate solution was investigated with varying pH and initial P concentrations. P removal was the highest at around pH 6. The pH range where P removal occurred was slightly wider at higher initial P concentrations. Compared to theoretical calculations, it was confirmed that AlPO4 precipitation was the main reason for P removal at low pH. At high pH, where there should be no AlPO4 precipitates, the P removal by adsorption of amorphous Al(OH)3 precipitates was experimentally observed. The P removal by adding amorphous Al(OH)3 precipitates prepared before the adsorption experiments, however, was lower than that by injecting aluminum sulfate solution because the prepared precipitates became larger, leading to less specific surface area available for adsorption. Ions other than sulfate had little influence on P removal.
The development of alternative water resources has emerged as an effective method for solving drought of water resources due to extreme weather and increase in water consumption. Recently, in Korea, there has been active research on reverse osmosis desalination technology, wastewater reuse using forward osmosis membranes, and the forward osmosis(FO)-reverse osmosis(RO) hybrid process combining these two technologies. In this study, the basic performance of FO membranes manufactured by three domestic and international manufactures such as Microfilter Co., Ltd., Toray Chemical Korea Inc., and Hydration Technologies Inc., were investigated for wastewater reuse. In addition, as an experiment to select feed solution, the selected membranes were operated 48 consecutive hours using three secondary effluents pretreated by the UF membrane with a pore size of 0.1 μm and auto strainer with pore sizes of 1 μm and 100 μm as feed solution. Although there was not much difference in the operating performance. Thus, the treated water using the 100 μm auto strainer was selected as feed solution applied to the assessment.
Disinfection of microorganisms using UV light is widely used in the field of water supply and wastewater treatment plant, In spite of high germicidal effect and relatively clean by-product, UV disinfection has fundamental defeat that is accumulation of fouling materials at the interface of water and lamp sleeve. Non-contact type of UV photoreactor which can avoid this fouling generation was developed and the experimental performance evaluation of the system was carried out in this study. Log inactivation rate of E. coli was selected as a disinfection index. The concentration of E. coli of second clarifier effluent was 8.2×101 - 8.2×103 colony per mL and was well inactivated by the non-contact type of UV photoreactor. Under the UV intensity condition of 2.1 - 2.5mW/cm2, E. coli removal rate was observed in the range of 54 - 95% when the HRT was increased from 10 to 52 seconds. Experimental results showed that log inactivation of E. coli was proportional to UV dosage and 200mJ/cm2 of UV dose is expected for the 2.0 log inactivation of E. coli from the second clarifier effluent. Between the two parameters of UV intensity and contact time which are consist of UV dose, UV intensity was 4 times more effective than contact time.s
The present study used the hydrodynamic numerical model, with the Reynolds-averaged Navier–Stokes equations (RANS) as its governing equations, to analyze overflow characteristics such as the discharge coefficient of circular-crested weir and the flow velocity and pressure distribution of weir crest. The simulation results well reproduced the overflow characteristics of the overfall of circular-crested weir both qualitatively and quantitatively. As for the discharge coefficient, rational results were yielded by the discharge coefficient equation proposed by Hager(1985) in the H1/Rb< 0.58 and by the discharge coefficient equation proposed by Samani and Bagheri(2014) in the H1/Rb> 0.58, respectively. Because most existing discharge coefficient equations were developed by disregarding the effects of the approach velocity, when they are applied, it is necessary to evaluate the effects of the approach velocity on the overflow head beforehand.
Pipe Deterioration Prediction (PDP) and Pipe Failure Risk Prediction (PFRP) models were developed in an attempt to predict the deterioration and failure risk in water mains using fuzzy technique and the markov process. These two models were used to determine the priority in repair and replacement, by predicting the deterioration degree, deterioration rate, failure possibility and remaining life in a study sample comprising 32 water mains. From an analysis approach based on conservative risk with a medium policy risk, the remaining life for 30 of the 32 water mains was less than 5 years for 2 mains (7%), 5-10 years for 8 (27%), 10-15 years for 7 (23%), 15-20 years for 5 (17%), 20-25 years for 5 (17%), and 25 years or more for 2 (7%).
This work investigated the decomposition of aqueous anatoxin-a originated from cyanobacteria using an underwater dielectric barrier discharge plasma system based on a porous ceramic tube and an alternating current (AC) high voltage. Plasmatic gas generated inside the porous ceramic tube was uniformly dispersed in the form of numerous bubbles into the aqueous solution through the micro-pores of the ceramic tube, which allowed an effective contact between the plasmatic gas and the aqueous anatoxin-a solution. Effect of applied voltage, treatment time and the coexistence of nutrients such as NO3 -, H2PO4 - and glucose on the decomposition of anatoxin-a was examined. Chemical analyses of the plasma-treated anatoxin-a solution using liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC) were performed to elucidate the mineralization mechanisms. Increasing the voltage improved the anatoxin-a decomposition efficiency due to the increased discharge power, but the energy required to remove a given amount of anatoxin-a was similar, regardless of the voltage. At an applied voltage of 17.2 kV (oxygen flow rate: 1.0 L min-1), anatoxin-a at an initial concentration of 1 mg L-1 (volume: 0.5 L) was successfully treated within 3 min. The chemical analyses using LC-MS and IC suggested that the intermediates with molecular weights of 123~161 produced by the attack of plasma-induced reactive species on anatoxin-a molecule were further oxidized to stable compounds such as acetic acid, formic acid and oxalic acid.
In this study, the RDII predictions were compared using two methodologies, i.e., the RTK-based and regression methods. Long-term (1/1/2011~12/31/2011) monitoring data, which consists of 10-min interval streamflow and the amount of precipitation, were collected at the domestic study area (1.36 km2 located in H county), and used for the construction of the RDII prediction models. The RTK method employs super position of tri-triangles, and each triangle (called, unit hydrograph) is defined by three parameters (i.e., R, T and K) determined/optimized using Genetic Algorithm (GA). In regression method, the MovingAverage (MA) filtering was used for data processing. Accuracies of RDII predictions from these two approaches were evaluated by comparing the root mean square error (RMSE) values from each model, in which the values were calculated to 320.613 (RTK method) and 420.653 (regression method), respectively. As a results, the RTK method was found to be more suitable for RDII prediction during extreme rainfall event, than the regression method.
In this study, a newly developed agitator with hydrofoil impeller applied to actual biological process in advanced wastewater treatment plant was evaluated. Several series of experiments were conducted in two different wastewater treatment plants where actual problems have been occurred such as the production of scums and sludge settling. For more effective evaluation, computational fluid dynamics (CFD) and measurements of MLSS (Mixed Liquor Suspended Solids) and DO (Dissolved Oxygen) were used with other measuring equipments. After the installation of one unit of vertical hydrofoil agitator in plant A, scum and sludge settling problems were solved and more than seventy percent of operational energy was saved. In case of plant B, there were three cells of each anoxic and anaerobic tanks, and each cell had one unit of submersible horizontal agitator. After the integration of three cells to one cell in each tank, and installation of one vertical hydrofoil agitator per tank, all the problems caused by improper mixing were solved and more than eighty percent of operational energy was found to be saved. Simple change of agitator applied to biological process in wastewater treatment plant was proved to be essential to eliminate scum and sludge settling problems and to save input energy.
Although the Hazen-Williams C factors are very important in the design, operation, and maintenance of water supply pipes, sufficient studies for them have been not reported in korea, which are based on experiments or measured data. Because of this, we have estimated C factors by measurement considering constraints in time precise safety diagnosis for multi-regional water supply system were performed. In this study, we confirmed constraints and variables characteristics of Hazen-Williams equation, and collected reliable C factors data of 174 by measurement, and analyzed their characteristics. According to collected data, the average value is 115.35, which is almost equal to the value of design standard or a little higher than it in korea. Also, among the equations suggested to determine C factor in the past, the C factors calculated by Sharp and Walski equation was closest to them in this study. In addition, to analyze collected C factors, use year and pipe diameter having high correlation with them were respectively divided into there categories. Analysis results showed that C factors evidently decreases depending on increases in use year, on the other hand, size of pipe diameter is proportional to value of them. In conclusion, this research showing evaluation and characteristics for C factors based on measured data will be used as practical reference in determining C factor in multi-regional water supply systems at a later date.
This study is focused on manganese (Mn(II)) removal by potassium permanganate (KMnO4) in surface water. The effects of bicarbonate on Mn(II) indicated that bicarbonate could remove Mn(II), but it was not effectively. When 0.5 mg/L of Mn(II) was dissolved in tap water, the addition of KMnO4 as much as KMnO4 to Mn(II) ratio is 0.67 satisfied the drinking water regulation for Mn (i.e. 0.05 mg/L), and the main mechanism was oxidation. On the other hand, when the same Mn(II) concentration was dissolved in surface water, the addition of KMnO4, which was the molar ratio of KMnO4/Mn(II) ranged 0.67 to 0.84 was needed for the regulation satisfaction, and the dominant mechanisms were both oxidation and adsorption. Unlike Mn(II) in tap water, the increasing the reaction time increased Mn(II) removal when KMnO4 was overdosed. Finally, the optimum conditions for the removals of 0.5 - 2.0 mg/L Mn(II) in surface water were both KMnO4 to Mn(II) ratio is 0.67 - 0.84 and the reaction time of 15 min. This indicated that the addition of KMnO4 was the one of convenient and effective methods to remove Mn(II).