WASTEWaste (also known as rubbish, refuse,

garbage, junk) is unwanted or useless materials. In biology, waste is any of the many unwanted

substances expelled from living organisms, metabolic waste; such as urea and sweat.

SOLID WASTE MANAGEMENT

Solid waste management is the process of collection, transportation and disposal of solid waste in a systematic, economic and hygienic manner. ‘Or’Solid-waste management is the process of the collecting, treating, and disposing of solid material that is discarded because it is of no longer use.

 TYPES OF SOLID WASTES

1.Based on physical nature:GarbageAshes Combustible and non-combustible wastes Demolition and construction wastes Hazardous wastes

Sources of Wastes

 Classification of wastes according to their origin and

typeMunicipal Solid wastes: Solid wastes that include household garbage, rubbish,

construction & packaging materials, trade refuges etc. are managed by any municipality.

Bio-medical wastes: Solid or liquid wastes including containers, products generated during diagnosis, treatment & research activities of medical sciences.

Industrial wastes: Liquid and solid wastes that are generated by manufacturing & processing units of various industries like chemical, petroleum, coal, metal gas,

sanitary & paper etc.

Agricultural wastes: Wastes generated from farming activities. These substances are mostly biodegradable.

Fishery wastes: Wastes generated due to fishery activities.

E-wastes: Electronic wastes generated from any modern establishments. They may be described as discarded electrical or electronic devices. Some electronic

scrap components, such as CRTs, wires, circuits, mobile, computers etc. 

 

THE MANAGEMENT OF THE SOLID WASTE IS DONE

ACCORDING TO ITS NATURE: Management of Medical solid waste

Management of non-degradable solid wasteManagement of Hazardous waste Management of non-hazardous &

biodegradable solid wasteManagement of electronic waste “e-waste”

i. Management of Medical solid waste: Hospital waste is generated during the diagnosis, treatment, or immunization of human beings or animals or in research activities in these fields or in the production or testing of biological. Medical solid waste includes both non-hazardous and hazardous waste constituents.

The non-hazardous waste Hazardous wastes

Treatment options: Incineration Sanitary landfill

ii. Management of non-degradable solid waste: Recycling Sanitary landfill Incineration

iii. Management of Hazardous waste: Treatment options-Thermal treatment

Incineration Biological treatment

  

iv. Management of non-hazardous & biodegradable solid waste:

 Non-hazardous solid waste is total waste including municipal waste, industrial waste, agricultural waste

and sewage sludge.Following methods are followed by management of

non-hazardous and biodegradable solid wastes: Open Dumps

Landfills Anaerobic Digestion

Composting Vermicomposting

METHODS FOR THE TREATMENT OF THE SOLID

WASTE: Open DumpsLandfillsAnaerobicDigestion Composting PyrolysisIncineration

i. Open Dumps: Open dumps refer to uncovered areas that

are used to dump solid waste of all kinds. The waste is untreated, and not segregated. It is the breeding ground for files, rats, and

other insects that spread disease. The rainwater run-off from these dumps

contaminates nearby land and water, thereby spreading disease. In some countries, open dumps are being phased out.

OPEN DUMP SITE

LANDFILLINGA landfill may also refer to the ground that has been filled in with soil and rocks instead of waste materials, so that it can be used for a specific purpose, such as for building houses . A landfill site is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. Historically, landfills have been the most common methods of organized waste disposal and remain so in many places around the world.The dumping is done with layers of 1- 2 m.The layer is covered with soil of 20 cm thickness. Landfill, also known as a dump or tip, is a site for disposal of waste materials by burial. Older, poorly designed or poorly managed landfills can create a number of adverse environmental impacts such as wind-blown litter, attraction of vermin, and generation of liquid leachate.

ADVANTAGES Landfill site is a cheap waste disposal option for the

local council. Jobs will be created for local people. Lots of different types of waste can be disposed of by

landfill in comparison to other waste disposal methods. The gases given off by the landfill site could be

collected and used for generating power.DISADVANTAGES The site will look ugly while it is being used for landfill. Dangerous gases are given off from landfill sites that

cause local air pollution and contribute to global warming.

Local streams could become polluted with toxins seeping through the ground from the landfill site.

Once the site has been filled it might not be able to be used for redevelopment as it might be too polluted.

ANAEROBIC DIGESTION: Anaerobic digestion is a regulated version of the natural events of landfill, in that it results in the controlled release of methane-rich biogas, which offers the potential for a very real form of energy from waste. It is carried out in large fermented tanks. In these tanks, solid waste is taken in the absence of oxygen and the anaerobic bacteria convert the large organic molecules mainly into methane CH4 and carbon dioxide CO2. Unlike composting, Anaerobic Digestion occurs at one of three distinct temperature ranges, namely:

Cryophilic (<20 ◦C) Mesophilic (20–45 ◦C) Thermophilic (>45 ◦C)

Micro-organisms involved in Anaerobic digestion: There are four main groups of bacteria involved in Anaerobic digestion, as shown below, with some typical examples of each: Hydrolytic fermentative bacteria – Clostridium and Peptococcus. Acetogenic bacteria – Syntrophobacter and Syntrophomonas. Acidogenic bacteria – Methanosarcina and Methanothrix. Methanogenic bacteria – Methanobacterium and Methanobrevibacterium.

The digestion process: The digestion process involves 4 steps. They are:

Hydrolysis Acidogenesis Acetogenesis Methanogenesis

Composting: Composting is the biological decomposition of organic waste under

controlled aerobic condition. Industries as paper, agricultural and food

processing give out wastes which are almost 100% organic. This organic matter can be composted to yield good manure.

Compost is the end product obtained after subjecting the organic fraction of solid waste to aerobic or anaerobic decomposition to yield humus like solid, carbon dioxide, water vapour and energy.

Different stages of composting: Segregation of solid waste Processing the compostable matter Preparation for compost Digestion Curing Screening

COMPOSITION CYCLE

Pyrolysis

Pyrolysis is defined as thermal degradation of waste in the absence of air to produce char, pyrolysis oil and syngas, e.g. the conversion of wood to charcoal also it is defined as destructive distillation of waste in the absence of oxygen. External source of heat is employed in this process.

Carried out at temp. between 500 ˚C – 1000 ˚C.

Gas, liquid and chars are the by products

INCINERATION:Incineration is the most common thermal treatment process. It is burning of the waste at a temperature of 1000°C ± 100°C in the presence of

oxygen so as to eliminate all odours and to ensure good combustion. After incineration, the wastes are converted to carbon dioxide, water vapour

and ash. It converts hazardous organic substances into less hazardous components.

 ADVANTAGES

Minimum of land is needed compared to other disposal methods. The weight of the waste is reduced to 25% of the initial value.

No risk of polluting local streams and ground waters as in landfills. Incineration plants can be located close to residential areas.

Gases are used to generate power. DISADVANTAGES

Expensive Required skilled labour.

The chemicals that would be released into the air could be strong pollutants and may destroy ozone layer (major disadvantage). high energy requirement.

The fundamental objective of waste processing is to reduce the amount of wastes through recycling and disposal of waste in a way not to impair environmental conservation.

Four R’s should be followed for waste management:

Refuse Reuse Recycle Reduce