Well It depend on your treatment system and what cost you want to take into acount. Do you mean only chemical cost or everything such as electricity, manpower costs, maintenance, etc.? Also since your concentration have a variation as well as your flow I would say it would be better to do the evaluation on load (kg of BOD and TSS) than concentration. What is the purpo0se of calculation those cost on concentration?
Yes you are correct. I meant to form the question interms of load instead of concentration. It's a conventional activated sludge plant and i am looking for cost of treatment to include everything(chemical,manpower,electricity).The reason for wanting to figure out the cost is because we have a local industry being charged one flat fee for loading overage and i believe they are not being charged enough. So i am wanting to figure out the cost of BOD and TSS per lbs.
Clearer for me now, thank you. I think that it would be best to base your evaluation with a real cost from previous year (taking into account if you lower or increase your expense for particular reason such as building new installation, big renewwal, etc.) and you should then get the total load for the same year. If for some reason your cost increase because of the high load from the industry you can take that into account too (what I mean is if for some reason lets say the electric company have different consumption fees based on level of consumption and you would fall in a lower level of charges if the industry would not be there). You really have to do a complete list to evaluate your cost.
Then you should do an actualization with your cost of this year and evaluate for the following few years (taking into account increase in price of your chemicals, electricity and all other fee). And do a relation between your cost and your loads.