Automobile industry is the fastest growing industry in the world, and with this growth, the production has grown too, with some key changes in the production process, the need for water treatment has become vital, not just to keep the carbon footprint at the lowest, but also to continue with the operations with lesser than, current damage to the environment.
And for this to work, installing water treatment plants is the pre-requisite, more specifically Effluent Treatment Plants (ETP). The ETP plays a major role in eliminating the pollutants and contaminants present in the water to an acceptable level before releasing it out in nature. There are major processes involved in ETP for automobile industries. They are:-
- Physical – Sedimentation (Clarification), screening, aeration, Filtration, Flotation and skimming, degasification, Equalization.
- Chemical – Chlorination, Ozonation, Neutralization, Coagulation, Adsorption, Ion exchange.
- Biological –
A. Aerobic – Activated sludge treatment methods, Trickling filtration, oxidation, ponds, lagoons, aerobic digestion.
B. Anaerobic – Anaerobic digestion, septic tanks, Lagoons .The treatment process can be sequenced as below:
I. Primary treatment – Removal of suspended solids, oil, grit etc.
II. Secondary treatment – Use of microorganisms in either aerobic or anaerobic condition for the reduction of the BOD, removal of color, oil and phenol.
III. Tertiary treatment – Use of electro dialysis, ion exchange and reverse osmosis for the final removal and purification of the wastewater.
The Automobile industry effluents which are discharged are treated with various physical and chemical treatments such as coagulation, flocculation, ozonation and biological treatment for the removal of nitrogen, phosphorous, organics and metal traces. The disadvantages of the physic – chemical processes are the formation of sludge, disposal of sludge and the space needed. The disadvantages of the biological processes are the presence of the toxic heavy metals which hamper the growth of microorganisms, most of the dye stuff used are no biodegradable in nature and the time requirement for the treatment is more. Automobile industry effluent contains chlorides, Paint impurities which are used to give paint on two wheeler and three wheeler parts by robots, Mineral oil from Coolant impurities which is used in machine shop. If coolant discharged in water it enhances COD of effluent. Automobile industry consist two treatment plants one ETP and other CTP.As compared with other industries parameters of automobile effluent is low and somewhat less organic and inorganic load is there. Recently Pollution control board is very strict about the ETP outlet water parameters. Health of environment is very important for better health of human beings. In past most of industries were sending their effluent without treatment but now it is not possible. Every industry is treating water carefully. Bajaj Auto is a leading company which is investing lot money to treat water without discharging a single liter effluent outside.
Necessity of ETP –
• To clean industry effluent and recycle it for further use.
• To reduce the usage of fresh/potable water in Industries.
• To cut expenditure on water procurement.
• To meet the Standards for emission or discharge of environmental pollutants from various Industries set by the Government and avoid hefty penalties.
• To safeguard environment against pollution and contribute in sustainable development.
ETP Plant Operation
1) Screen chamber: Remove relatively large solids, plastic bags, and bottles to avoid abrasion of mechanical equipment’s and clogging of hydraulic system.
2) Sedimentation Tank: This a large capacity Zigzag tank. In this tanks water is allowed to run slowly in zigzag direction so whatever the suspended matter of paint is present it will settle down and supernatant water will flow ahead which is less turbid than earlier.
3) Collection tank: The collection tank collects the effluent water from the sedimentation tank, stores and then pumps it to the equalization tank.
4) Equalization tank: The effluents have fluctuate concentrations at all the time; the pH will vary time to time. Effluents are stored in the equalization tank resulting in a homogenous mixing of effluents and helping in neutralization. Automobile industry Effluent has acidic PH sometimes alkaline. Lime is used to neutralized acidic PH .Mostly Lime is used because it is cheap than caustic soda . Continuous mixing also eliminates settling of solids within the equalization tank. Reduces SS, TSS.
5) Flash mixer: Coagulants were added to the effluents: Lime: (800-1000 ppm) To correct the pH up to 8-9
6) Flocculation Tank : In the clarriflocculator the water is circulated continuously by adding polymer and stirred continuously. Overflowed water is taken out to the aeration tank. The solid particles and dissolved paint it will stick to polymer and it float on water and collected separately and dried; this reduces SS, TSS. Flocculation provides slow mixing that leads to the formation of macro flocs, which then float out on the clarifier zone and turbid water is converted into clear water. The flock’s i.e. primary sludge is sent into lamella clarifier.
7) Lamella clarifier In this clarifier flocks are allowed to trap into screen bars and it is sent to sludge beds for drying. Clear water passed to secondary tanks.
8) Secondary treatment In this tank water will be free from turbidity having higher alkaline PH. Alkaline PH is neutralized by dosing dilute sulphuric acids. Nowadays hydrochloric acid is not used for neutralization.
9) Biological treatment Neutralized water is allowed to pass into Bioreactors. Bioreactor tank contains Mycobacteria populations in large quantity. Which convert organic and inorganic chemicals into carbon dioxide and water in presence of Oxygen. All COD and BOD load is reduced in this tank. Bioreactors are the backbone of ETP.
10) Clarifier The overflow water which is treated is allowed to come in bottom of clarifier. Along with water from bioreactor some population of bacteria will come in clarifier .That bacteria sludge is re-circulated in Bioreactors again to maintain constant population. If sludge will increase in bioreactor tanks it can be taken to sludge bed for few minutes based on MLSS and Sludge Volume Index.
11) Post Aerator The overflow water from clarifier is passed into post aerator .Here Dissolved oxygen level of treated water is increased at normal level. This water has normal range of PH, TDS, TSS, COD, BOD, Oil and Grease, phosphate, chlorides .all parameters are within Pollution control board. Automobile industries have set up online PH meter on every tank like inlet, outlet tanks. There are online TDS, TSS, COD, BOD meters which record the parameters correctly and display on monitor of manager’s computer. So need of chemist is very less for analysis .All instruments are calibrated monthly for more accuracy.
However, the treatment varies from client to client and some additional steps maybe added or omitted depending upon the effluent to be treated, or the requirement of the treated water. the above said is a basic hands on example of what a treatment plant would look like for automobile industry, we at HYPER FILTERATION do customized solutions with regard to client’s requirements. Hence, ensuring better results than our adversaries in the business.