Solid Waste | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) PDF Download

Chapter 7

 Solid Waste And Domestic Wastewater Management

Domestic Wastewater: Domestic wastewater, originating primarily from individuals, undergoes a multi-step treatment process for effective management.

Primary Treatment

• Screening: Removes large objects like stones or sticks to prevent blockages.
• Grit Chamber: Slows down the flow, allowing grit to settle.
• Sedimentation Tank: Settleable solids are removed, and oils are skimmed off.

Secondary Treatment: Utilizes biological processes where microorganisms convert non-settleable solids to settleable ones. Common options include:

• Activated Sludge: Uses microorganisms with aeration and agitation for organic material breakdown.
• Trickling Filters: Wastewater trickles through media, aiding microorganisms in breaking down organic material.
• Lagoons: Relies on sunlight, algae, microorganisms, and oxygen.

Post-Treatment: After primary and secondary treatments, chlorine or other disinfectants are used. Some facilities also employ tertiary treatment to remove nutrients and chemicals.

SOLID WASTE

Solid waste includes organic and inorganic materials like packaging, grass clippings, furniture, and more, lacking value for initial users.

Solid Waste Management

It involves controlling waste generation, storage, collection, transfer, transport, processing, and disposal, considering public health, economics, engineering, conservation, aesthetics, and environmental factors.

WASTE CHARACTERISTICS

• Density: Important for landfill design and storage; compaction increases density.
• Moisture Content: Influences weight and incineration costs.
• Size: Essential for mechanical separators and shredders.
• Field Capacity: Critical to avoid leachate formation in landfills.
• Permeability: Governs liquid and gas movement in landfills.
• Compressibility: Affects physical changes under pressure.

Chemical Characteristics:

• Lipids: High heating values suitable for energy recovery.
• Carbohydrates: Biodegrades to water and methane; attracts flies and rats.
• Proteins: Partial decomposition produces amines with unpleasant odors.
• Natural Fibers: Resistant to biodegradation; suitable for incineration.
• Plastic: Suitable for recycling or incineration; PVC produces dioxin and acid gas.
• Non-Combustibles: Includes glass, ceramics, metals, dust, and ashes.

Waste Generation And Collection

Waste generation occurs during raw material processing and continues at each production step. Reducing solid waste involves limiting raw material consumption and promoting recovery and reuse. Waste collection includes various components like collection points, frequency, storage containers, crew, route, transfer stations, and vehicles. Various disposal options include uncontrolled dumping, sanitary landfills, composting, incineration, and gasification.

Recycling:

Recycling involves separating, collecting, processing, marketing, and reusing materials that would otherwise be discarded. Commonly recycled materials include paper, cardboard, glass, metals, plastics, bacteria, and tires.

RECOVERY OF BIOLOGICAL CONVERSION PRODUCTS:

• Composting: Biochemical degradation of organic waste yields a humus-like product suitable for soil conditioning.
• Biogasification: Biogas, primarily methane, is produced by bacteria during the anaerobic degradation of organic material. It is used for energy recovery.
• Incineration and Energy Recovery: Incineration involves the combustion of waste, generating heat for energy recovery in the form of steam used for electricity generation or heating.
• Efficient waste and wastewater management require comprehensive strategies addressing environmental concerns, public health, and sustainable resource use.