Waste refers to unwanted materials produced by human activities.

CLASSIFICATION OF WASTES

Wastes can be classified based on different criteria: physical state and degradability.

Classification Based on Physical State

• Solid Wastes: Non-liquid, non-gaseous materials, such as food scraps, paper, and plastics.
• Liquid Wastes: Waste in liquid form, including sewage and wastewater.
• Gaseous Wastes: Emissions and gases released from industrial processes.
• Sludge Wastes: Semi-solid waste, often produced from wastewater treatment.

Classification Based on Degradability

• Biodegradable Wastes: Materials that can decay relatively quickly due to microbial action, including food scraps and yard waste.
• Non-Biodegradable Wastes: Materials that do not decompose naturally, such as plastics and glass.

SOURCES OF WASTES

1. Domestic Sources: Food leftovers, plastics, metals, untreated sewage, expired medications.
2. Industrial Sources: Used oil, toxic gases, metals, and plastics.
3. Agricultural Sources: Plant remains, excess pesticides, herbicides, and weedicides.
4. Medical Sources: Plastics, glassware, expired drugs, used syringes, and needles.
5. Laboratory Sources: Expired chemicals, broken glassware, and contaminated materials.

WAYS OF TREATING AND DISPOSING WASTE

• Open Burning: Incineration of waste materials in open areas. This method is discouraged due to air pollution.
• Incineration: Controlled burning of waste in incinerators, which reduces volume and emissions.
• Dump Sites: Uncontrolled disposal areas for waste, leading to potential air and water pollution.
• Sanitary Landfills: Burying solid waste in layered, compacted forms, designed to minimize environmental impact.
• Composting: Aerobic decomposition of organic waste to create nutrient-rich compost for agriculture.
• Recycling/Re-use: Reprocessing materials to prevent waste. For example, used bottles can be repurposed for storage.

WAYS OF MINIMIZING WASTE

Waste can be minimized through:

• Recycling: Processing materials for reuse.
• Reusing: Finding new uses for discarded items.
• Reduction at Source: Decreasing waste generation by using fewer materials.

RECYCLING OF METALS AND PLASTICS

Recycling proceeds as follows:

1. Collection: Gathering recyclable materials from waste disposal sites.
2. Sorting: Organizing materials by type, color, and manufacturing method.
3. Cleaning: Removing impurities from recyclable materials.
4. Resizing: Shredding materials into smaller pieces for easier processing.
5. Identification: Testing particles for quality and classification.
6. Compounding: Melting and reshaping materials into pellets for new products.

IMPORTANCE OF RECYCLING METALS AND PLASTICS

• Preservation of Natural Resources: Reduces the depletion of raw materials.
• Reduction of Emissions: Lowers greenhouse gas emissions associated with manufacturing.
• Economic Development: Saves costs on mining and processing, allowing funds to be directed to other development programs.
• Cost Savings: Generally lower costs for recycled materials compared to new materials.