Treating Alkaline Wastewater
What is Alkaline Wastewater?
Alkaline is defined as having a pH of more than 7. Other terms for alkaline are high pH and basic. The pH scale measures how acidic or alkaline (base) a substance is. The scale is logarithmic and each pH value above 7 is ten times more alkaline than the next level. So, for example, a pH of 9 is ten times more alkaline than a pH of 8 and one hundred times more alkaline than a pH of 7.
- What are some common alkaline wastewaters?
Many of the most common industrial wastewaters successfully processed in wastewater evaporators are alkaline in nature. Parts cleaning wash waters, vibratory / tumbling wash waters, compressor condensate wastewaters, dye penetrant wastewaters, floor scrubbing wash waters, and some plating rinse waters all tend to be alkaline.
- What are the concerns with alkaline wastewater?
Wastewater with a pH above 12.5 is considered corrosive by RCRA and is labeled as hazardous. In terms of evaporation, high pH wastewater poses a few concerns.
1. One is that alkaline wastewater has a higher tendency to foam. As you can see in the listing of common alkaline wastewaters above, many of those wastewaters contains soaps and detergents, so the possibility of foaming is to be expected.
2. The other concern is that, depending on the type of alkalinity of the water, it may have a higher tendency to scale. Calcium, strontium, barium, and magnesium based salts can be rather insoluble and may scale.
...Many of the most common industrial wastewaters successfully processed in wastewater evaporators are alkaline in nature...
- Can I use an Evaporator if my alkaline wastewater foams?
In almost all cases, the answer is YES! In our over 20 years of providing evaporation technology, we have found the solutions below to be very effective.
1. Elementary pH Adjustment: Just as alkaline wastewater has a higher tendency to foam, using elementary pH adjustment to lower the pH to neutral or slightly acidic often minimizes or eliminates the tendency to foam.
2. Antifoam: Using a high temperature antifoam or defoamer can be a simple and economical way to greatly reduce or eliminate foam. There are many antifoam chemistries available and they can be formulated to target specific applications. Most high temperature antifoams use silica to pop the foam bubbles while also reducing the surface tension that allows the foam to form in the first place.
3. Reduce Heat Input (BTU rate) on Burners: Some foams are exacerbated by the vigor of the boil itself. Soapy water is an example of this type. Reducing the BTU rate to the burner will reduce the vigor of the boil and often greatly reduce or eliminate this type of foam. Reduced heat input will reduce the system evaporation rate, but many of our customers have excess evaporation capacity thereby making this form of foam control feasible.
- Can I use an Evaporator if my alkaline wastewater tends to scale?
In most cases scale build up is a non issue. If it does occur, it is usually minor and occurs over a length of time. Scaling is monitored as part of routine maintenance by visually checking the tank and heat exchanger after each dump of residue and cleaned as needed. If necessary, ENCON Service Engineers will work with our customers to recommend chemistry to effectively descale wetted parts in their evaporator. ENCON Service Engineers can also work with our customers to recommend anti-scalent chemistry as a preventive measure .
- How can I tell if my wastewater is a good candidate for evaporation?
The centerpiece of our consultative approach is the wastewater qualification process. Not all waste streams are good candidates for evaporation. We believe it’s better to find that out in our laboratory than on your factory floor.
This analysis also helps determine materials of construction and allows us to determine operating procedure recommendations. If more detailed analysis of specific parameters is needed, ENCON can prepare appropriate samples and send them for outside lab analysis for a nominal cost (prices for analytical tests vary).
Once the analysis is complete, your Sales Engineer will deliver a report detailing the results to you. This report includes material of construction and pH adjustment recommendations, if needed. This allows you to make an informed decision if an ENCON evaporator is right for you.
Use the quick question form on the bottom, or call us at (603) 624-5110.
It all starts with your initial conversation with an ENCON Sales Engineer. These experts take the time to truly understand your needs and your own unique wastewater challenges.
Their thorough knowledge of the wastewater industry in general and evaporation technology in particular allows them to manage ENCON’s resources toward addressing your unique wastewater disposal project.
They’ll get to know the processes in your plant that generate wastewater. How you currently deal with it. Even what processes you might implement in the future that may affect the volume and quality of your wastewater. This allows them to help you select the right evaporator for today and tomorrow.