How to Dose Effluent Treatment Plant Chemicals?

Effluent Treatment Plants treat industrial effluent, making it safe for disposal or reuse. The treatment involves various chemical dosages that help to neutralize, decompose, or remove contaminants from the effluent. Proper chemical dosing is necessary to the success of the treatment process, and improper dosing may lead to ineffective treatment, increased operating expenses, and environmental non-compliance. In this blog, we’ll go over the importance of chemical dosing and how to dose ETP chemicals correctly.

What is Chemical Dosing in ETP Plants?

Chemical dosing in ETP plant is the process of adding some chemicals to the wastewater to enable treatment. Chemicals are added at some steps of the treatment cycle, i.e., coagulation, flocculation, neutralization, and disinfection. Chemicals must be dosed in an appropriate amount otherwise they will fail and even produce wastage and toxic side effects.

Chemicals Used in ETP Plants

· Coagulants (Alum, Ferric Chloride)

· Flocculants (Polyacrylamide, Polyaluminum Chloride)

· Alkaline Chemicals (Lime, Sodium Hydroxide)

· Acidic Chemicals (Sulfuric Acid)

· Disinfectants (Chlorine, Ozone)

All the chemicals are dosed at different stages of the treatment process to remove all the impurities such as suspended solids, heavy metals, oils, and pathogens efficiently.

Dosing ETP Chemicals

Dosing of the Coagulant:

Coagulation is the first treatment step of wastewater treatment wherein chemicals like Alum or Ferric Chloride are added to neutralize charges on particles so that they will agglomerate and stick together to create large clumps (flocs). Coagulant dosing helps in the removal of suspended solids and large particles from the effluent.

How to Dose

· Begin by finding the amount of coagulant needed via jar tests. During a jar test, one uses different dosages of coagulant and tests them in order to find the ideal dose.

· Compute the effluent rate of flow so as to get the total coagulant needed.

· Add the necessary amount of coagulant to the wastewater by dosing pump. The dose rate is generally pre-set for the intended flow rate and concentration.

Key Consideration

· Weak flocculation and hence poor removal of particles and prolongation of the process result from under-dosing or over-dosing of the coagulant.

Flocculant Dosing

After coagulation, flocculation occurs. Flocculants like Polyacrylamide cause aggregation of minute particles into bulky flocs that get separated by settling or filtration.

How to Dose:

· Just like in coagulants, conduct a jar test in order to determine the best kind and amount of flocculant to use with the given effluent.

· The dosing for flocculant will generally be less compared to coagulants because the latter are stronger.

· Dosing adjustment according to type of wastewater to get the right dosage of flocculant to enable particles to clump properly.

Key Consideration

· Mist dosing produces excessive fine particle formation, and it leads to faulty separation and excess sludge.

Alkaline Chemical Dosing

Alkaline chemicals like Lime or Sodium Hydroxide are used in a way to condition the wastewater to some extent of more favorable pH. Acidic wastewater is neutralized and space is allowed for other treatment processes like coagulation and flocculation to be most effective.

How to Dose:

· Measure the current pH of the wastewater and establish the amount of alkaline chemical which will be needed to achieve the optimal pH.

· Concentrate the alkaline chemicals and dose the chemicals by means of a metering pump with amounts that are measured.

· Regular checks on the pH must be taken in order to confirm that the intended pH is continually being achieved.

Key Consideration

· Excessive dosing of alkaline chemicals will increase pH too much and will impact treatment process, and less dosing will lead to an inadequate neutralization of acid wastewater.

Acid Chemical Dosing

Acid chemicals like Sulfuric Acid are used in order to neutralize alkaline effluent or pH adjustment of the effluent. Acid dosing is essential if industrial effluent contains higher pH due to chemical reaction.

How to Dose:

· Similar to alkaline dosing, the pH level should be measured and the amount of acid should be calculated to achieve the required level.

· Prepare the acid solution and dose through a chemical dosing pump.

· Monitor the pH of effluent after dosing at regular intervals to ensure the best pH is obtained.

Key Consideration

· Chemicals employed in acid must be handled carefully since they are toxic. Always see to it that the right concentration and appropriate protection gear are at hand.

Disinfectant Dosing

Disinfectants like Chlorine or Ozone are used at the last stage of wastewater treatment to disinfect bacteria or pathogens, if any, left before discharging or reusing the effluent.

Dosing Procedure:

· Disinfectants are dosed usually on the basis of residual disinfectant concentration that needs to be present in the treated water.

· For the dosing of chlorination, analyze the free chlorine residual and dose the amount of chlorine needed using a dosing pump.

· If Ozone is utilized, make sure the ozone generator is set to the proper level of water to be treated.

Key Consideration

· Disinfectant overdose provides toxic chemical residues in water, while under-dosing will not give total disinfection. An individual should have a balance to get an effective treatment.

Practical Chemical Dosing Tips in ETP Plants

· Regular Monitoring: Regular monitoring of influent and effluent quality for effective chemical dosing.

· Use Automated Dosing Systems: Use automated chemical dosing systems variable with respect to flow rate and contaminant concentration for accurate dosing.

· Training of Operators: Adequate training of operators in a way that they are aware of the chemicals, dosages, and safety measures.

· Preventive Maintenance: Regular inspection of the dosing equipment like pumps, valves, and tanks to avoid leakage or collapse that may disrupt dosing accuracy.

Conclusion

Chemical dosing is one of the most essential parts of running an effective and efficient ETP plant. The right chemicals, in the correct amount, at the correct time, ensure that wastewater is treated to the desired level. If operators are aware of the optimum dosage, continuously monitor the treatment process, and use the proper dosing equipment, then the effectiveness of the effluent treatment plant can be optimized to a significant extent. Never forget that under-dosing or over-dosing of chemicals will be detrimental to the operation of treatment, but also to the operating cost as well as compliance with environmental regulation. Therefore, routine maintenance and routine maintenance on the chemical dosing is the most important factor in an effort to maximize from your ETP plant.

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