TULSA, Okla.— Wastewater concerns from laundries seem to be turning into a bigger topic these days. More restrictions are coming down from the Environmental Protection Agency (EPA) to our local publicly owned treatment works (POTW). This, in turn, is passed on to local companies, especially laundries. 

While there are several methods to work on your wastewater, the most common are dissolved air flotation (DAF) units or ceramic filters. My company has both. One of our plants operates a DAF unit, and the other operates a ceramic filter. I thought I would give an overhead view of what I see in both of our facilities and how they are working. 

I don’t operate them every day, so there are certainly employees in our facilities who have more knowledge than I do. However, I see the results from both, so here are my observations.

First of all, they both work very well. You will meet techs who swear by one method or the other, but I do believe both systems require something unique that makes one method more suitable for your facility than the other one might. That is exactly why we have one facility with a DAF unit and the other with a ceramic unit. We are a food-and-beverage and healthcare laundry.

DAF units have been around the longest of the two methods. This method is usually easier to plan for when constructing a new facility because you must be able to store your wastewater. The more wastewater that can be stored before the DAF unit, the better. This allows the rinse waters and the break waters to balance themselves out a little before they enter the DAF unit.

An operator needs to adjust the chemicals before the DAF so that it can work properly. The more consistent the water is, the easier the DAF is to run, so the less likely you are to get friendly reminders from your POTW to treat your water. Depending on how good your operator is, you can control your costs and stay within the range of the POTW. 

The sludge that is removed from the water will get dewatered and hauled off to your landfill. But this method does take an operator to monitor it and work with your dewatering method. We use a press to remove the water. In the past, we used a vacuum pump that would remove the water. Depending on how large a facility you have, this can be a time-consuming process. 

You must figure in removing this dried sludge to a bin so that you can haul it to the landfill. Access to an exit is imperative. DAF units are great, but they do require some space to install them. They do not by themselves reuse any water. 

Most companies just treat the water enough to get under the POTW limits. For the best results, an operator needs to keep a close eye on the unit throughout the day. The initial investment is usually not as large when purchasing a DAF unit.

Ceramic filters are basically just filters that you are pumping your wastewater through to remove your oils and greases. No pretreatment is needed; no huge storage tanks are required. 

If your system is large enough to handle the gallons per minute (GPM) your washroom is discharging, you will love it. Naturally, the more wastewater you can hold, the better, because you cannot speed the system up. If your system can handle 150 GPM, you just need to make sure you can store enough water so that you can average 150 GPM feeding it. Be careful not to undersize these units. 

The advantage of a ceramic filter is that, overnight, your POTW will think you turned into wastewater experts. Why? Unless you have extremely low limits, you will be under your limits the first time you turn it on. You can reuse this water in your break steps or early rinses. This is not potable water and cannot be used in final rinses. 

You can add a reverse osmosis system to further treat your water, and then you can reuse almost all of it. 

At night, the system will clean itself; an operator should, however, keep an eye on it. The oils and grease stay in liquid form and are sent to a tank where you can have it hauled off. 

On a day-to-day basis, a ceramic filter seems to be easier to operate than a DAF. They do seem to go through more seals and valves, but you are not tying the maintenance tech’s time up dealing with the system all day. We pretty much turn it on and walk away; it is not checked again until we start the clean cycle at the end of the day. 

The initial investment can be fairly large when purchasing a ceramic unit.

I tried to keep both descriptions fairly short. An entire article can be written on how each system works independently, so I did not go into detail on either. These are just my observations on what we go through with our systems.