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Chapters- 1 - 2 - 3 - 4 - 5 - 6 - 7

CHAPTER - 3

* WM Techniques


1.1 Waste Minimisation Techniques



1.1 Waste Minimisation Techniques
Waste Minimisation options or measures could be grouped into three major categories
1. Waste Reduction at Source
2. Recycling
3. Product Modification

Waste Reduction at Source options are sub-divided into "Good Housekeeping" and "Process Change" Options.

Good Housekeeping, usually means changing existing practices or introducing new ways of operating and maintaining equipment. Appropriate provisions to prevent spills and to encourage good workplace attitudes are included in this category of waste minimisation options. Good housekeeping options are normally inexpensive and their pay-back period is short.

Repair leakages, close taps when not in use, raw material conveyor to reduce material handling losses, insulation of digesters etc.
Process Change includes four types of options: Change in raw material, Better Process Control, Equipment Modification and Technology change.

Change of raw material options includes the use of less hazardous materials or raw materials of higher quality aimed at reducing the quantity / toxicity of waste generated from the process. Existing raw materials could be substituted with less polluting ones.

Substituting existing toxic dyes with non-toxic dyes to reduce effluent and product toxicity, use of H202 bleaching instead of chlorine based bleaching to avoid generation of toxic adsorbable organic halides ( AOX ).

Better process control aims at optimising the process parameters / conditions like pH, temperature, pressure, residence time etc., to ensure operation of the existing processes at higher efficiency and with lower waste and emission generation. This may be achieved for example, by training the operators or by adding monitoring and control devices to the machinery.

Example : Optimisation of pulping process for extended cooking with NaOH.

Equipment modification includes small changes to existing equipment, such as installing drip pans, installing fluid coupling in blenders, pumps activation through level controlling mechanisms etc., which aims at reducing the waste generation caused due to poor equipment design. This may be achieved for example, by training the operators or by adding monitoring and control devices to the machinery.

Technology change constitutes the replacement of technology, processing sequence and / or synthesis pathway in order to minimise waste and emission generation during the production process.

Installation of Screw press and counter current multistage vacuum washers for pulp washing.

Recycling is the-on-site recovery and reuse of wasted materials and energy. The recovered materials may either be reused in the same process or used for another purpose, for example in producing useful by-products, like creation of ligno sulphates from black liquor or lignin recovery from black liquor for use as soil conditioner.


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