I.Definition of Wastes
Waste can be described as “any substance or object the holder discards, intends todiscard or is required to discard”, as defined by the Waste Framework Directive(European Directive (WFD) 2006/12/EC), (amended by the new WFD (Directive2008/98/EC, coming into force in December 2010).In the Philippines’ Republic Act No. 9275 (An Act Providing For aComprehensive Water Quality management and for Other Purposes), waste means “anymaterial either solid, liquid, semisolid, contained gas or other forms resulting fromindustrial, commercial, mining or agricultural operations, or from community and household activities that is devoid of usage and discarded.”
II.Classification of Wastes
The classification of wastes varies and depends country by country. Waste can bedivided into many different types. The most common method of classification is by their physical, chemical, and biological characteristics.
1. Solid Waste- Solid waste is broadly defined as including non-hazardous industrial, commercialand domestic refuse including household organic trash, street sweepings, hospital andinstitutional garbage, and construction wastes; generally sludge and human waste areregarded as a liquid waste problem outside the scope of MSW (Zerbock, 2003).These arewaste materials that contain less than 70% water. Example of this type of waste are thedomestic or household garbage, some industrial wastes, some mining wastes, and oilfieldwastes such as drill cuttings.
2. Liquid Waste-These are usually wastewaters that contain less than 1%. This contain high concentration of dissolved salts and metals. Liquid wastes are on ftenclassified into two broad types: sewage and toxic wastes. Generally, there are varioustypes of liquid waste generated in urban centers: human excreta, domestics wastes produced in households, hospital wastes, industrial effluents, agricultural liquid wastesand nuclear wastes. When improperly handled and disposed of, liquid wastes pose aserious threat to human health and the environment because of their ability to enter watersheds, pollute ground water and drinking water (US EPA, 2009)
3.Sludge-It is a class of waste between liquid and solid. They usually contain between 3%and 25% solid, while the rest of the material is dissolved water.
4. Hazardous Waste-Hazardous wastes are wastes which, by themselves or after coming into contactwith other wastes, have characteristics, such as chemical reactivity, toxicity,corrosiveness or a tendency to explode, that pose a risk to human health or theenvironment. Hazardous wastes are generated from a wide range of industrial,commercial, agricultural, and to a much less extent, domestic activities. They may takethe form of solids, liquids or sludges, and can pose both acute and chronic public healthand environmental risks