Pasig River is an important river in the Metro Manila, Philippines, since it provides food, livelihood and transport to its residents, and connects two major water bodies; Laguna de Bay and Manila Bay. However, it is now considered to be the toilet bowl of Metro Manila due to the large amount of wastes dumped into the river. Even with the efforts of the government to revive the quality of the Pasig River and its tributaries, it continues to deteriorate over time. This paper provides an overview of the current condition of the Pasig River. The existing water management policies were reviewed, and the issues and challenges hindering the improvement of its water quality identified. Moreover, the water qualities of the rivers in Metro Manila were compared to those of the major rivers in South Korea. The current watershed management system practiced by South Korea has been discussed to serve as a guideline for future recovery of the water quality of the rivers in the Philippines.

This study investigated the potential of using bottom ash to be used as an adsorbent for the removal of lead (Pb) from aqueous solutions. The physical and chemical characteristics of bottom ash were determined, with a series of leaching and adsorption experiments performed to evaluate the suitability of bottom ash as an adsorbent material. Trace elements were present, such as silicon and aluminum, indicating that the material had a good adsorption capacity. All heavy metals leached during the Korea standard leaching test (KSLT) passed the regulatory limits for safe disposal, while batch adsorption experiments showed that bottom ash was capable of adsorbing Pb (experimental q e = 0.05 mg/g), wherein the adsorption rate increased with decreasing particle size. The adsorption data were then fitted to kinetic models, including Lagergren first-order and Pseudo-second order, as well as the Elovich equation, and isotherm models, including the Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The results showed that pseudo-second order kinetics was the most suitable model for describing the kinetic adsorption, while the Freundlich isotherm best represented the equilibrium sorption onto bottom ash. The maximum sorption capacity and energy of adsorption of bottom ash were 0.315 mg/g and 7.01 KJ/mol, respectively.

Effective control of nonpoint source pollution in urban areas relies on the appropriate application of best management practices (BMPs). Many strategies are used in designing the BMPs considering efficiency, cost, benefits, etc. In Korea, the first flush criterion is typically employed to size the BMPs. However, the criterion was only adopted from foreign literature without verification of its applicability. This study was conducted to investigate the most suitable first flush design rainfall that can be used in sizing the BMPs in Korea. The data used to calculate the pollutant concentrations were gathered from a total of 22 storm events during the three-year monitoring on a paved parking lot site. The magnitude of the generated first flush at 5 mm and 7.5 mm accumulated rainfall were quantified and analyzed by means of mass first flush (MFF) ratio. The results showed that the pollutant concentration at 5 and 7.5 mm accumulated rainfall were 36% and 22% greater than the average event mean concentration (EMC), respectively. Although the BMP size could be appreciably reduced by almost 70% when 5 mm rainfall is to be used as compare to 50% size reduction for 7.5 mm rainfall, it is still better to select 7.5 mm as design rainfall. In this case, the treated mass is above 50% for 7.5 mm but only 40% for 5 mm rainfall. Therefore, "cost-effective" BMP design must not only depend on treated runoff quantity but also quality of the treated runoff.

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