Hi Kavita,

First of all, I think it should be usefull to mention the objective of the chlorination. It is for desinfection in order to produce drinking water? or the goal is to oxidize some poluttant of a wastewater prior to discharge? (i.e. several organic compounds present ussualy in industrial wastewaters may be destroyed by appliyng chlorine. Cyanide containing wastewaters are often chlorinated in order to destroy such compound previously to the discharge into a river, sewage, or any water body).

In every case, I reccomend you to pay attention to the "chlorine demand" of the liquid. This means the chlorine consumed by all the another components of the sample. For instance, if you want to desinfect water, each oxidable compound (organic and/or inorganic) will consume some amount of chlorine. Therefore you will need an additional amount of reagent in order to reach your goal.

Usually, for drinking water you will try to get some "residual" chlorine on treated liquid in order to ensure the absence of microorganisms re-growing, even after the treatment (while water is storaged in a tank of is running for the distribution network you want certain Chlorine concentration remaining). If the chlorine demand of the raw liquid is cero (very strange case) and you know the goal value (i.e. 0.2 mg/L) you could calculate the chlorine amount by simple stochiometry and dilution calculations. But if the liquid has many oxidable compounds, you should know that in order to use aditional chlorine. Several books presented methods to measure experimentally the "chlorine demand". 

The main cost should be only the chlorine reagent cost. Ussually it is expressed as equivalent grams Cl2 / liter. As you may know, you can choose several commercial forms of chlorine (gas, NaClO solution, Ca(ClO)2, chloramines, and others). The grams Cl2 / liter is a standard way to express the chlorine liberated by the chlorination agent when it reacts. You can calculate if you know the chlorination agent reaction in the water.

You may find detailed information for each chlorination agent in several books. I suggest : White´s Handbook of chlorination and alternative disinfectants, 5º edition, Black & Veatch Corporation, Wiley and sons inc., 2010.

As you mention "dechlorination" I guess perhaps you don´t need residual desinfection activity. In those case "residual chlorine" = cero and you only must satisfy the "chlorine demand" of the raw liquid. This situation happen when you use chlorine to destroy some pollutant. Personally, I haven´t experience on industrial dechlorination processes. I guess the cost depends of the dechlorination agent (on books you will find a lot) and how much chlorine you should remove. If you improve the chlorination step, avoiding unnecessary chlorine, the dechlorination also will be cheaper.

Regarding power consumption, I´m not sure how significative it is when you compare with the reagents cost. In small processes (talking about my country, Argentina) the reagent cost is far higer than the power requiered to pump a chlorine solution. Of course, you will need a pump to run the system in a continuous way. If you want to reduce operation cost, a good option is to use an automatic dosing system. On this case, the initial investment will be a quite higher, but operation cost will be low.  If you use gaseous chlorine or some solid chlorine source, you should consider another devices (mixers, disolution tanks, gas valves and cylinders) and each case should be studied separately. 

I hope it help,

Regards,

Sergio

 Hello Sir.

I really appreciate your response. Thank you so much. I have used chlorine in the form of Calcium hypochlorite to disinfect secondary treated wastewater in batch process for a lab scale study. I have choosed an optimised dose of chlorine (4 mg/L for 20 minutes) to acheive the norms of 1000 cfu/100 mL. Dechlorination was also carried out at the end of each process. Power consumption was of magnetic stirrer as I have placed my batch reactor on stirrer for proper mixing. So, I want to calculate total cost of the chlorination process for this lab scale study.

I think now the whole scenario will be clear to you. i will now wait for your suggestions for costing purpose.

 Hello Sir.

I really appreciate your response. Thank you so much. I have used chlorine in the form of Calcium hypochlorite to disinfect secondary treated wastewater in batch process for a lab scale study. I have choosed an optimised dose of chlorine (4 mg/L for 20 minutes) to achieve the norms of 1000 cfu/100 mL. Dechlorination was also carried out at the end of each process. Power consumption was of magnetic stirrer as I have placed my batch reactor on stirrer for proper mixing. So, I want to calculate total cost of the chlorination process for this lab scale study.

I think now the whole scenario will be clear to you. i will now wait for your suggestions for costing purpose.

Hi Kavita,

If you already know the chlorine dose, you should know the cost of Ca(ClO)2 used in the experiment. The same with dechlorination agent. It is correct?

About the magnetic stirrer, I guess the power cost should be negligible, but it depends of electricity cost at your working place.

I think the bigger cost will be on the reagents. If you need a detailed cost analysis, you can also consider the depreciation cost of the laboratory equipment employed (glass material, stirrers, pH-meters, and so on) and the operators working cost (your and your fellows time) . It depends of how deep you want to do such calculation. Usually, for lab scale it isn´t necessary.

If you like to estimate the power cost you may:

- Check the Intenstity of power consumption (Amperes) in the electrical label of the mixer, or

- Measure the intensity with an amperometric device on the stirrer wire

Then, you can multiply Intensity by Voltage of your network (usually 110 or 220V) and obtain the Power (Watts). P=V*I

For total power consumption along the experiment, you should multiply the Power by the experiment time, obtaining the Energy consumed (W*hour).  If you know the electricity cost per Watt*hour in your country/region, just multiply to obtain the power cost.

I´m not sure if this information is that you were looking for, or if you need another data. Anything, write again and I will try to help.

Regards,

Sergio

Hello Sir...                                                                                                                                            Thank you so much once again. This is actually what I want. Your guidance will help me a lot. I will surely contact you in case of any doubt.

Good afternoon Sir.

Can you please give me links of few research papers having details on costing of Chlorine, UV and Ozone disinfection for small scale treatment plant? I have downloaded few papers but they are either of large scale or important details are not mentioned. 

Good afternoon Sir.

Can you please give me links of few research papers having details on costing of Chlorine, UV and Ozone disinfection for small scale treatment plant? I have downloaded few papers but they are either of large scale or important details are not mentioned.