Effluent is a liquid waste (wastewater) generated by factories, hotels, vehicle service centres and other commercial business units. As it contains high level of BOD, COD, TSS and TDS, it puts negative effect on the water and soil. The high level of BOD significantly decreases dissolved oxygen (DO) level; hence, it puts fresh water resources in danger. In today’s scenario it is imperative to treat industrial wastewater to a level where it can be reused safely or drain out without affecting the environment. CPCB and other statuary bodies have set some guidelines for wastewater that every effluent treatment plant must follow
Different treatment methods and levels of effluent treatment plant (ETP):
Here, are the 3 wastewater treatment methods used in ETP for Chemical industry to reduce the potential impact on the environment.
1. Physical Treatment Methods
2. Chemical Treatment Methods and
3. Biological Treatment Methods
Water that we recovered after all these treatment levels can be recycled and reused for various area like Back to re-use, Gardening, Cooling tower, Irrigation etc.
Design of effluent treatment plant is completely depending upon the nature of effluent and the sources from which it is generated. Generally, ETPs undergoes four (4) treatment levels such as preliminary treatment level, primary treatment level, secondary treatment level and tertiary treatment level. All these treatment processes/levels have the potential to treat the effluent from Chemical industry and bring down its parameters to the permissible ones.
1. Pre-treatment or preliminary treatment level:
Being a first treatment level, it removes coarse solids and other large materials that are found in effluent to avoid damage to subsequent treatment units. Preliminary treatment operations typically include coarse screening, grit removal and, in some cases, breaking of large objects into the smaller objects. Partially treated wastewater is now subjected to next treatment level called primary treatment level.
2. Primary treatment level:
It’s objective is removal of large solids from the wastewater via physical settling or filtration. It
involves separation of floating material and heavy solids from liquid waste. The primary clarifiers can effectively remove 50-60% of the suspended solids. Oil and grease, organic nitrogen, organic phosphorus, and heavy metals associated with solids are also removed during primary sedimentation.
3. Secondary treatment level:
The major purpose of this treatment level is to remove suspended solids and residual organic matter which can be done using aerobic and anaerobic processes. The activated sludge process is the most common option in secondary treatment. It involves aeration tank where oxygen is supplied to the microorganisms which results in removal of biodegradable dissolved and colloidal organic matter.
4. Tertiary treatment level:
The purpose of this treatment level is to further improve the effluent quality before it is discharged to the receiving environment. It removes the contaminants that were not removed in previous treatment levels. It involves disinfection process (using chlorine, UV light, ozone) which leaves no harmful residues that would need to be removed from the wastewater after treatment.