INTRODUCTION

1.1 Significance of the Study

The Pasig River runs through Metro Manila in the Philippines. It is approximately 32 Km long and serves as the drainage outlet for most of Metro Manila. It is fed by several tributaries like the San Juan and Marikina Rivers, and the outlet for the 700,000-acre Laguna Lake. In the 1980’s and 1990’s, it is one of the most polluted rivers in the Philippines. In 1998, the population of Metro Manila increased to 11 million, and there were around 12,000 industries using the Pasig River and 315 of these were considered as major water polluters (Bautista, 1998).

Presently, the banks of Pasig River are lined with industries, commercial establishments, institutions, residential areas, and open spaces. Most firms have been intensively using the river as their dumping ground of solid, liquid, and toxic waste. Only few industries practice waste treatment process before discharging waste into the river. Effluent standards do not establish a limit on the total load released in a given time period. This allows some establishments to dilute their waste to meet effluent concentration standards and encourage excessive use of water.
Presently, the river has fallen below a “Class D” category . According to DENR studies, during the dry season many portions of the river are considered biologically dead.

Some pollutants, particularly oxygen-demanding organic wastes and nutrients, are so common and have a profound impact on almost all types of rivers that they deserve special emphasis. This is not to say that they are always the most significant pollutants in any river, but rather that no other pollutant category has as much overall effect on rivers (Davis, 1998).

Activated carbon (AC) can be prepared from a large variety of carbon-containing feedstocks by the activation of pyrolyzed char. The most common feedstocks for the commercial production of activated carbons are anthracite and bituminous coal, lignite, peat, and the lignocellulosic materials wood and coconut shells (Polard et al., 1992). Plentiful agricultural by-products such as sugarcane bagasse, rice straw, soybean hulls, rice hulls, and nutshells are lignocellulosic wastes that may offer an inexpensive and renewable additional source of activated carbons. Such carbons may have the potential to replace existing carbons, especially coal-based carbons used in many industrial applications including the removal of color and odor compounds in aqueous systems and removal of colorants from raw sugar (Ahmedna, et al., 2000a).

Activated Carbon treatment of wastewater is usually thought of as a polishing process for water that has already received normal biological treatment. The carbon in this case is used to remove a portion of the remaining dissolved organic matter.

Complete treatment with activated carbon is also being studied as a possible substitute for biological treatment of municipal wastewater when site limitations or industrial waste components pose problems for biological processes (Tchobanoglous, 1991).

Philippine coconut production reported from 1990-1996 ranges from 11M- 12M metric tons per year, around 1-2 M of which are shells that are made into charcoal and AC (as cited in Arquero, 2002).

This study evaluated the locally made coconut shell activated carbon, which we also export today. Their export potential is huge. The results help us in determining if its quality is competitive compared to the AC made abroad.

Plans of using the Laguna Lake as the source of potable water for Metro Manila are ongoing. The need to clean our water resources and the abundant supply of coconut shells justified the conduction of this study.

1.2 Objectives

The general objective was to lower the COD of the samples taken from the Pasig River using local coconut shell activated carbon.
The specific objectives of the study were:
1. to characterize the Pasig River water samples in terms of pH, turbidity, color, chloride content, and COD;
2. to characterize the AC (iodine no., moisture content, and bulk density);
3. to determine the equilibrium contact time;
4. to determine the pH necessary for maximum adsorption;
5. to determine the rate of adsorption of solute onto AC;
6. to determine the minimum amount of AC that will have satisfactory COD reduction.


1.3 Date and Place of the Study

The study was done from June 2003 to October 2003. Characterization and pretreatment of AC were done at the Dept. of Chemical Engineering, CEAT, UP Los Banos. The characterization of the Pasig River water sample and the batch adsorption experiment were conducted at the Regional Standards and Testing Laboratory of DOST Regional Office No. IV located in Los Banos, Laguna.

1.4 Limitations of the Study

The effect of temperature on the COD reduction of the sample by activated carbon was not determined, as the study was done using ambient temperature only. No effort was made to make the Pasig River water samples as the representative samples of that part of river as they were taken only from the surface and near the banks