Optimization

Optimization may be defined as an act, process or methodology of making something (design, system or decision) as fully perfect, functional or effective as possible. This tells the operator what it is, but not how to achieve it, in the treatment plant, either wastewater or drinking water.

Optimization is making the best wastewater effluent or the best and safest potable water that a plant can possibly make, while minimizing costs.

You might say “but we’re already making good water. It meets all the numbers, and we are in compliance and have no bad bacteriological samples. All our effluent numbers look good, everything is fine. Why change it? That just makes more work for me.”

One of the responsibilities of a wastewater or drinking water operator is to do the best that he or she can, everyday and provide the public with safe, quality drinking water or produce the best effluent possible from the wastewater plant. In order to do this, things always have to change.

The influent may not change, but one day you may think, “What if I increase the return activated sludge (RAS) rate and make the mixed liquor volatile suspended solids (MLVSS)  more concentrated in the aeration basin? Will that remove more biochemical oxygen demand (BOD) faster?” You make the change, open the RAS valve half a turn, post it in the log book, let it run for 24 hours and then put it back (and log it). This increases the MLVSS by a certain percentage, which enhances the BOD removal.

Or you think, “I wonder if another one or two PPM of cationic polymer added at the quick mix will lower the top of filter (TOF) turbidity by .2 Nephelometric turbidity units (NTU)?” You decide to run a set of jar tests to determine if the additional polymer fed will have any effect on the TOF turbidity. If so, how much polymer and at what dosage? How much effect does it have on the TOF turbidity and what will it cost to increase the feed rate of the polymer?

These are just two very simple examples of how to start to optimize a treatment plant. Ask a question, put together a plan, even if it is only on a scrap of paper, of what you can do to answer the question and then try to find the answer through process control testing or observation of changes to the plant.  Let everybody that you work with know what your plan is and ask permission, if necessary, to put your plan into action.

Optimization is a process.  Once you have the .2 NTU drop on the TOF or the increased BOD removal, go to the next question and continue the process. It never stops. There is always a way to make it better.

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