End - of - Pipe Treatment

Effluent Treatment Plant

The textile industry consumes large quantities of water for different processes and the effluent generated is discharged into various receiving bodies like public sewers, lakes, ponds, rivers and nallahs etc. This effluent is contaminated with dyes and chemicals. While some of these contaminants are non-biodegradable others have high oxygen demand. This waste water destroys the quality of water in which they are disposed thereby affecting the flora, fauna and human life also.

In the recent times the textile finishing sector on one hand has to pay substantial amount towards fresh water charges and effluent treatment charges and on the other hand has to strive hard to meet more stringent effluent regulations. The treatment options are based on the concentrations of dyes, auxiliaries & chemicals, types of chemicals, and also norms of pollution control board based on types of disposal.

It is now widely accepted by the dye house managements, on environmental and economic grounds, that they must treat the effluent before discharging into water bodies on a continuous basis. Therefore, it becomes essential to opt for an efficient working effluent treatment plant. Various methods of effluent treatment are known but in most of the methods, the treatments costs are high.

Designing of effluent treatment plant is a complex work because varying nature of effluent coming from various operations of textile processing and has variable characteristics. Hence it becomes necessary to consider the following factors before the construction/designing of effluent treatment plant.

1. Quantity or the profile of the effluent to be treated.
2. End use of the water reclaimed.
3. Pattern of hourly flow and daily flow of effluent.
4. Characteristics of effluent from each drain.
5. Characteristics of combined effluent from the drain.
6. Possibility of segregation of widely varying effluents and treating them separately.
7. Treatment options available by pilot trials.
8. The available outlets for removal of the dewatered sludge.
9. Possibility of reuse of treated effluent.

Following are some of the more common methods of treatment followed throughout the world:

1. By using various flocculation decolourisation of the effluent can be carried out and it can be partially reused.

2. Various oxidation treatments like spurge pipes, surface aeration ejectors, diffusers, helixors, and oxygen and also chemical oxidation treatments can be employed for decolourisation of the effluent.

3. Fenton reagent used for waste water treatment is based on it's oxidizing efficiency which is highest at pH ranging from 2 to 5, and molar H₂O₂ to Fe₂⁺ ratio is about 1:1.

4. The combination of UV radiation and hydrogen peroxide (UV/H₂O₂ involves an oxidative degradation of the noxious substances.

5. Bagasse, the waste material generated in sugar mills has been us for the removal of chromium nickel, copper and lead from aqueous solutions. Bagasse has been pretreated with 0.1 N NaOH followed by 0.1 N CH₃COOH for effective removal.