Cooling Tower Evaporation Credits – How to Reduce Sewer Charges

Cooling tower evaporation credits or sewer credits are compensation received for not draining water. Your local water municipality charges twice. First for delivering the water, and second for draining the water into the sewer system. Cooling towers, however, are unique in that around 75% of the water is evaporated and is not drained. As a result, you can receive a water utility refund, often referred to as evaporation credits or sewer credits. This is one of many efforts that should be done to reduce your overall cooling tower expenses.

 

Most municipalities offer this for cooling towers since it saves them money on maintaining sewers and treating wastewater. The following steps should be taken to receive a cooling tower evaporation/sewer credit:

Here are some examples of the official government registration processes in several major cities that Chardon Labs services:

Louisville, NYC, Racine, Washington, D.C.

If your municipality does not have specific registration processes or documentation publicly available, contact them for specific information.

This drawing should indicate the flow of water in the cooling tower. Include the source (makeup water), bleed valve, fill, etc.

This is the “credit meter”. There are several different names for this: sub-meter, deduct meter, private meter, sewer meter, etc. Its functionality is to measure the amount of water you are draining and not evaporating from the cooling tower.

Some municipalities will want to inspect the cooling tower to have it activated. You should now be receiving evaporation/sewer credits.

Each municipality will charge a different percentage for the supply and sewerage of water. A simple example of this would be if the municipality charges 50% for supply and 50% for sewer on a $1,000 monthly bill. Each would cost $500, then if you receive an evaporation credit, your bill would become $500 instead of $1,000.

A quality water treatment program will prioritize water savings, requiring less water to be bled from the cooling tower. This, in conjunction with evaporation credits, will save a considerable amount of money. One of the best ways to achieve this is to increase the cycles of concentration. Cycles of concentration describe the number of times water is recirculated in the cooling tower before it is bled. The reason water is bled is that it leaves scale deposits, biofilm, and can corrode the system. Untreated water would become worse and worse as these issues can build up. You can cycle the water more if you chemically treat the water and utilize a water softener. The number of times you can do this depends on the treatment and the makeup water quality. For example, Toledo, OH, water is naturally hard and will have a lower cycle concentration than Baltimore, MD. Evaporation credits can show whether a company is treating your water properly or just bleeding it constantly to prevent problems.

 

In addition to monitoring water consumption by the cooling tower for sewage credit, it is essential to record the amount of water used by the tower system every month. Our sales team bases the contract price for cooling tower service on water usage, and precise knowledge of changes in the usage rate gives us data on which to base contract prices.

 

Keeping track of the amount of water consumed each month can provide other useful information. It can indicate the amount of chemical usage necessary.

 

Another important reason we record water meter readings on every service call is to confirm that the amount of inhibitor used during the period correlates with the amount that should have been used. Recall that most of our cooling tower controllers base inhibitor feed on make-up water.

 

Valuable troubleshooting information may be learned by comparing the amount of water used during the past month with the amount that has been pumped out of the batch tank. Ideally, the two values are equal, and the inhibitor level in the tower water at present is within the appropriate range.

 

Given our ability to calculate the amount of inhibitor the tower system will require over a given amount of time, it is possible to determine how much inhibitor will be required to ensure that the batch tank does not run out before your next service call.

 

This may be accomplished in two ways. First, by increasing the volume of the batch tanks that hold the inhibitor, we can be confident that it will hold an adequate volume to maintain a continuous supply to the tower for at least one month. Secondly, the concentration can be increased so that fewer batches are required for every 100 gallons of make-up water.  The batch strength should be concentrated enough to allow 2-3 months of operation without preparing more inhibitor batches.

 

Biocide use rates are based on the total tower system volume and the severity of the microbiological problem. The dose rate of most biocides is based on ounces of biocide per 1,000 gallons of system water. It is therefore imperative to know the total system volume. Recall that the EPA sets stringent guidelines on the maximum legal concentration of each biocide. Exceeding this maximum legal concentration can be very costly.

 

It is not recommended to dose above set EPA recommendations. Doses above this could make the chemical less effective or compound other problems in the system, both of which reduce the account’s profitability by using more biocide than necessary. Using less biocide than needed becomes obvious quickly as bacterial slime and algal growth accumulate on visible tower surfaces, but using too much biocide is rarely visible and often goes unnoticed until the profitability of the account is reviewed, and it is discovered that you are using twice as much biocide as projected. Spending a few minutes with a calculator can literally save thousands of dollars.

 

 

Chardon Labs can assist with the issuance and tracking of cooling tower evaporation credits (sewer credits). To reach out to us for assistance, click here!