Classify the solid wastes giving suitable example

 Classify the solid wastes, giving suitable example for each of them. Also explain the different methods of disposal of solid wastes.

Solution:

Refuse represents the dry wastes or solid wastes of the society except human excreta and sullage. It includes garbage, ashes, rubbish, dust, etc.

(i) Garbage includes all sorts of putrescible organic wastes obtained from kitchens, hotels, restautants, etc. All waste food

articles, vegetable peelings, fruit peelings, etc., are thus included in this term.

(ii) Ashes denote the incombustible waste products from heaths and furnaces, and houses or industries.

(iii) Rubbish includes all non – putrescible wastes except ashes. It, thus includes all combustible and non- combustible wastes such as rage, paper pieces, broken pieces of glass and furniture, card boards, broken crockery, etc.

Besides the technical classification based on the type of wastes, the refuse may also be classified, depending on its source, as: (i) house refuse; (ii) street refuse and (iii) Trade refuse.

Collection of refuse: The refuse is generally collected in individual houses in small containers and from there, it is collected by sweepers in small hand driven lorries/carts and then dumped into the masonry chambers constructed along roadsides by municipalities. The refuse is finally carted away by municipal trucks, for further disposal during some day time.

Disposal of refuse:

The refuse can be disposed of by various methods, such as

(a) Sanitary land filing: In this method of refuse disposal, refuse is carried and dumped into the low lying area under an engineered operation, designed and operated according to the acceptable standards, as not to cause any nuisance or hazards to public health or safety. Area method and trench method are two methods of land filing which are usually adopted.

(b) Burning or incineration: Burning of refuse at high temperatures in furnaces called incinerators is quite a sanitary method of refuse disposal and is widely adopted in USA where the refuse is of high calorific value and hence quite suitable for burning. The heat produced during burning of the refuse is used in the form of steam power for running turbines to generate electricity.

(c) Barging it out into the sea: This method may be used to dispose of refuse by throwing it away into the sea, after carrying it at reasonable distance from the coast. The sea depth at such disposal point should not be less than 30m or so, and the direction of the currents should be as not to bring it back towards the shore.

(d) Pulverization: In this method refuse is pulverized in grinding machine, so as to reduce its volume and to change its physical character. The grinded or pulverized refuse becomes practically odorless and unattractive to this insects.

(e) Composting: It is biological method of decomposing solid wastes. This decomposition can be effected either under aerobic or anaerobic conditions or both. The final end product is manure called compost or human, which is in great demand as fertilizer for farms.