Most cost-effective way to lower process water alkalinity
Most cost-effective way to lower process water alkalinity
(OP)
I need to design a process that lowers the alkalinity of 50,000 L/day of water. The water in question required 34.2 mL of 0.02N H2SO4 to neutralize 100ml and I need to lower the alkalinity to where the same amount can be neutralized by 25 mL of 0.02N H2SO4. I am currently thinking to develop an acid-injection system, but I am not sure if this is the best route. I am new to this site and professional engineering, so feel free to give tips on both!
Let me know if this information is not sufficient. Thanks!
Will Bryant
Let me know if this information is not sufficient. Thanks!
Will Bryant





RE: Most cost-effective way to lower process water alkalinity
RE: Most cost-effective way to lower process water alkalinity
Alkalinity Test (Volume of 0.02N H2SO4 Required to Neutralize 100mL Sample Using Mixed Indicator (mL))
Results: 38.1
Limit: 25.0 Max
Acidity Test (Volume of 0.02N NaOH Required to Neutralize 100mL Sample Using Mixed Indicator (mL))
Results: NIL
Limit: 5.0 Max
Inorganic Solids (ppm)
Results: 497
Limit: 3000 Max
Sulphates As SO3 (ppm)
Results: 80
Limit: 400 Max
Chlorides Cl (ppm)
Results: 107
Limit: 2000 Max For Plain Concrete
500 Max For Reinforced Concrete
Suspended Matter (ppm)
Results: 15
Limit: 2000 Max
Organic Matter (ppm)
Results: 143
Limit: 200 Max
pH
Result: 8.0
Limit: Not Less than 6
The treated water will be used by a construction contractor, not sure on specifics but I can find out. The facility should be a long-term treatment plant, and I am not sure on the ability of the workers. This will be taking place in India. As far as the cost and availability of acid, I have someone looking for that information already and I will post results as I get them.
RE: Most cost-effective way to lower process water alkalinity
RE: Most cost-effective way to lower process water alkalinity
RE: Most cost-effective way to lower process water alkalinity
Also, can anyone recommend a good reference manual for piping and control systems for this type of application?
I am thinking to use a system design similar to the setup recommended by Bimr for an RO acid-injection system here: http://www.eng-tips.com/viewthread.cfm?qid=79099
I am glad that this is a relatively small application; I still can't believe I count as a licensed engineer, fresh out of school, in India!
RE: Most cost-effective way to lower process water alkalinity
Look at introducing sulphuric acid via a metering pump into a closed top box from the above with an air break. Have the process water introduced submerged tangentially into the box so that you get a circular swirling pattern. Put vertical baffles on all four sides so that the water gets mixed with the acid. Use special carpenter stainless steel. Have another box in series to give the mixed water more mixing just to make sure. It is similar to designeing hydraulic flocculation tanks
No mechanical mixing requried....no issues with heat generated at the acid water interface .etc etc.
You have to understand the properties of the acids that you are contemplating to use. Acids are never easy to handle. Off gass from a HCL a day tank vent will offgases and will corrode any steel in a room. The room will look like hell in short order
RE: Most cost-effective way to lower process water alkalinity
You should note the sodium concentration will increase as you lower the pH.
RE: Most cost-effective way to lower process water alkalinity
RE: Most cost-effective way to lower process water alkalinity
It appears that very little acid will be required. What is the purpose of the neutralization and what will the water be used for.
RE: Most cost-effective way to lower process water alkalinity
In regards to the mixing boxes, is there any sizing calculations for the size of the box, location of the feed, and width of the baffles? I am guessing that with such a low acid feed rate, I could just build it large and turbulent enough so as to guarantee proper mixing without them, but its probably best to double-check.
Thanks again for both of your extremely helpful responses!
RE: Most cost-effective way to lower process water alkalinity
You should be aware that a process control system will be necessary to safely feed acid inline. Each flow should be monitored and controlled. If the water stops, then the acid feed must be shut off. A pH meter should also be used to shut the system down if the finished solution is out of specification.