Importance and methods of waste management

Wastewater and solid waste are produced every day by every household, market, hospital and industry. If they are not collected, treated and disposed of properly, they cause disease, bad smell, pollution of water and soil, and loss of property value.

Importance of management

• Public health: untreated sewage carries pathogens that cause cholera, typhoid, dysentery, hepatitis and diarrhoea. Heaps of garbage breed flies, rats and mosquitoes.
• Protection of water sources: it prevents pollution of rivers, lakes and groundwater that supply drinking water downstream.
• Environment and aesthetics: it removes foul odour, clogged drains and dumped refuse, and so keeps the city clean and attractive.
• Prevents flooding: blocked drains full of solid waste cause urban flooding (as seen in Kathmandu's rivers and drains).
• Economic benefit: treated water can be reused for irrigation, biogas and compost can be produced, and tourism and land value improve.
• Legal duty: the Local Government Operation Act and the Solid Waste Management Act, 2068 make local bodies responsible for the service.

Methods (components) of wastewater management

1. Collection: house connections, lateral and main sewers, appurtenances (manholes, inlets) carry sewage by gravity to one point. Systems are separate, combined or partially separate.
2. Treatment: preliminary (screens, grit chamber), primary (sedimentation), secondary (trickling filter, activated sludge, oxidation pond) and sometimes tertiary treatment.
3. Sludge treatment: thickening, digestion and drying beds.
4. Disposal: by dilution in a river or lake, or on land (irrigation, sewage farming). On-site systems (septic tank, pit latrine) serve areas without sewers.

Methods of solid waste management

Generation -> Storage -> Collection -> Transfer
   -> Transport -> Treatment/Resource recovery -> Disposal

1. Source reduction and segregation into organic, recyclable and residual waste.
2. Storage and collection in bins, door-to-door vehicles.
3. Transportation by tractors, tippers, compactors, often through a transfer station.
4. Treatment and recovery: composting, biogas, recycling.
5. Final disposal: sanitary landfill, incineration (for hospital and hazardous waste).