The effect of permanganate oxidation was investigated as water treatment strategy with a focus on comparing the reaction characteristics of NaOCl and sodium permanganate (NaMnO4) in algae (Monoraphidium sp., Micractinium inermum, Microcystis aeruginosa)-contained water. Flow cytometry explained that chlorine exposure easily damaged algae cells. Damaged algae cells release intracellular organic matter, which increases the concentration of organic matter in the water, which is higher than by NaMnO4. The oxidation reaction resulted in the release of toxin (microcystin-LR, MC-LR) in water, and the reaction of algal organic matter with NaOCl resulted in trihalomethanes (THMs) concentration increase. The oxidation results by NaMnO4 significantly improved the concentration reduction of THMs and MC-LR. Therefore, this study suggests that NaMnO4 is effective as a pre-oxidant for reducing algae damage and byproducts in water treatment process.
In this study, we collect water control valves that have had accidents due to existing cracks, etc. are collected, and propose investigation items for strengthening the valve structural safety evaluation through a series of analyzes from valve specifications to physicochemical properties are proposed. The results of this study are as follows. First, there was a large variation in the thickness of the body or flange of the valves to be investigated, which is considered to be very important factor, because it may affect the safety of the valve body against internal pressure and the flange connected with the bolt nut. Second, 60% of the valves under investigation had many voids in the valve body and flange, etc. and the decrease in thickness due to corrosion was relatively large on the inner surface in contact with water rather than the outer surface. It is judged that the investigation of depth included voids is very important factor. Third, all valves to be investigated are made of gray cast iron foam, and therefore it is judged that there is no major problem in chemical composition. It is judged that the chemical composition should be investigated. Fourth, as a physical investigation item, the analysis of metal morphology structure seems to be a very important factor for nodular cast iron from rather than a gray cast iron foam water valve with a flake structure. As it was found to be 46.7~68.8% of the standard recommended by KS, it could have a direct effect on damage such as cracks, and therefore it is judged that the evaluation of tensile strength is very important in evaluating the safety of the valve.
In order to overcome the small scale of Korea waterworks and to achieve comprehensive improvement and innovation transformation, the waterworks integration was reviewed. The effect of consolidation was confirmed by the integration of the water supply business in the southern Gangwon region and the western Gyeongnam region in Korea, such as an increase in the flow rate and a decrease in the production unit cost. After facing management and service limitations overseas, more than 1,000 small-scale waterworks projects in the UK were integrated into 27 waterworks providers, and Japan also revised the Waterworks Act in December 2019 and is in the process of integrating waterworks. It is considered appropriate to promote the integration of waterworks projects in Korea by respecting the autonomy of local governments, but using a participatory method, a win-win method, and a linkage method. For the integration of waterworks projects, three strategies are proposed: First creating a national foundation for integration (revision of the Waterworks Act), Second establishing a waterworks integration strategy led by local governments, Third forming an external consensus and providing incentives for participation.
Mangyeong River and Dongjin River are highly dependent on external regions for domestic and agricultural water, and the agricultural water supply and use system of those rivers are very complicated. For smooth water supply, rivers are used as a supply system. Of the total river water use permits (as of 2019), agricultural water accounts for 97.5%, 80.4% in Mangyeong River and Dongjin River, respectively. The excessive intake of river water as agricultural purpose is causing the stream to dry out and to deteriorate the ecological health of the river. It is necessary to minimize the water use system that takes in and utilizes river water. In both rivers, the flow rate of agricultural drainage and the load of major water quality items that flowing into the main stream are similar to or higher than those of the major tributaries, indicating that management is necessary to improve the water quality of the river. It is necessary to understand the effect of agricultural drainage on river water quality by establishing a continuous monitoring system for the form of agricultural drainage.