Liquid and solid wastes- Environmental problems and management

Wastes are the material that are not needed and are not usable economically with further processing. It may be in the form of solid, liquid, and gas. They originate from the human activities such as agriculture, industry, domestic activities etc. According to origin, waste is classified as domestic, industrial, commercial, clinical, construction, nuclear, and agricultural. According to properties waste is classified as degradable, non-degradable,  inert, toxic, and inflammable. If these wastes remain untreated, it leads to air, water, soil or solid waste pollution. Hence, solid waste management is very essential.

Solid wastes are categorized as municipal waste, industrial waste, and hazardous wastes. Municipal waste arises from domestic activities of human beings. Industrial waste arises from industrial activities and hazardous wastes are the substances which causes hazard to plants, animals and human beings. Few of the common hazardous waste is radioactive substances, chemicals, biological wastes, flammable wastes and explosives.

The causes of waste generation are Over population, Urbanization, Affluence, Technological change (returnable glass container or bottles are being replaced by non-returnable cans, plastic containers, plastic bottles etc.)

Effect of Solid Waste

Pollution Solid waste can pollute air, water and soil, and leave various environmental impacts, and cause health hazard, due to improper handling and transportation. These adverse effects are seen on health and environment, some of them are as follows:

Environmental impacts

Leachates from refuge dumps percolates into the soil and contaminate underground water.  Scavengers and stray animals invade the roadside garbage and litter the waste over large area causing much aesthetic damage to the atmosphere. Waste products when burnt like plastic and rubber pollute the atmosphere with noxious fumes.  Organic solid wastes emits obnoxious odor on their decomposition and make the environment polluted.  Accumulation of heavy metals and nutrients. Immobilization of nitrogen and loss of biodiversity

Health hazards

Vectors like rats and insects invade refuse dumps and spread various diseases. During handling and transfer of hospital and clinic wastes, disease transmission may take place.  Water and food contamination through flies causes various diseases in humans as dysentery, diarrhea and amoebic dysentery.  Rats dwelling with infectious solid wastes may spread diseases like plague, salmonellosis, trichinosis, endemic typhus etc. Water supply, if gets contaminated with pathogens present in solid wastes, may result in cholera, jaundice, hepatitis, gastro enteric diseases etc.  Choking of drains and gully pits by the solid wastes results in water logging which facilitates breeding of mosquitoes and results in the spread of diseases like malaria and plague.

Minamata  is a case of human mercury poisoning which occurred in Minamata bay in Japan. A large plastic plants located near the Minamata bay used mercury to produce vinyl chloride, the left over mercury was dumped into bay which entered in tissues of fish, which in turn were consumed by people living in that area. The contaminated fish thus caused an outbreak of poisoning, killing and affecting several people.

Types of liquid waste and potential negative impacts

Businesses produce a variety of liquid wastes, including hazardous and non-hazardous waste. Types of waste include chemical liquids – like solvents, fertilizers and paints – which are often hazardous and produced in large quantities.

Surface Water Pollution: Liquid waste has the ability to alter water’s chemical composition. It can happen slowly – i.e. a slow leak at a chemicals processing plant – or all at once from a large-scale oil spill. In turn, drinking water can be contaminated, and aquatic ecosystems can be disrupted. Depletion of dissolved nitrogen by the organic pollutants deaths of fishes occur. Nitrates and phosphates  present in the  effluent can cause eutrophication. Nitrates over and above the prescribed level will cause the disease called “blue baby syndrome”

Soil Contamination: Liquid waste can quickly seep into the earth. This pollution can cause harm to plants growing in the soil, as well as to animals or people who consume foods that were created in contaminated soil. The effluent in the soil will deplete the available nitrogen in the soil there by it will change the diversity of the species. Chlorides present in the waste water will kill the beneficial soil microbes. 

Air Pollution: Although air pollution is more commonly associated with dust, gas and fine particle contamination, liquid wastes can also impact air quality. For example, foul smells are common with liquid waste pollution, particularly with sewage systems.

In Tamil Nadu alone, the ETPs generate about 100 tonnes of tannery sludge per day (dry basis). As the sludge contains relatively higher concentration of chromium, it is classified as hazardous material. Tannery industrial sludge is alkaline in nature (pH 7.5 to 10). Tannery industrial sludge are rich in N, especially organic N, but very poor in P. Tannery sludge contain sulfide, which impart high antibacterial activity along with chromium and organic compounds.

Management of Solid Waste

Disposal

It is done most commonly through a sanitary landfill or through incineration. Landfills- a modern sanitary landfill is a depression in an impermeable soil layer that is lined with an impermeable membrane. In it solid waste is placed in a suitably selected and prepared landfill site in a prescribed manner. The waste material is spread out and compacted with appropriate heavy machinery. The waste is covered each day with a layer of compacted soil.

Incineration: it is the process of burning municipal solid waste in a properly designed furnace under suitable temperature and operating conditions. It reduces the municipal solid waste by about 90% and 75% by weight.

Composting: bacterial decomposition of organic components of the municipal waste result in the formation of humus or compost and the process is known as composting. It helps in disposal of solid waste, disposal of night soil, and production of valuable manure for crops, it is also termed as biodegradation.

Recycling It means reusing some components of the waste that may have some economic value. Recycling conserves resources, reduce the energy used during manufacture and also reduce pollution.

Source recovery (pyrolysis):  it is a kind of destructive distillation in which the solid wastes are heated in pyrolysis reactor at 650-1000 degree centigrade in oxygen depleted environment. By this process, the chemical constituents and chemical energy of some organic wastes are recovered. The organic constituents split up into gaseous liquid and gaseous fractions like carbon dioxide, carbon monoxide, tar, methane, charred carbon etc.

Source reduction : it is one of the fundamental ways to reduce waste. This can be done by using less material when making a product, reusing products, designing products packaging to reduce their quantity. Individually one can reduce the use of unnecessary items which causes solid waste.