How Much Magnesium Hydroxide Alkalinity Do I Need to Add for Wastewater Treatment?

How Much Magnesium Hydroxide Alkalinity Do I Need to Add for Wastewater Treatment?

Wastewater Treatment Plant operators use alkalinity as a tool to control and optimize biological activity for efficient wastewater treatment. Proper alkalinity control contributes to expanded water treatment capacity, better permit compliance, cleaner discharge, better use of capital, better process control, lower risk of process upset, and avoids smelly sulfur bacteria!

To find out how much alkalinity is needed for wastewater treatment, use standard methods to collect wastewater samples and test the following: Influent ammonia, in mg/L; Influent total alkalinity, in mg/L; Effluent total alkalinity, in mg/L; Wastewater volume treated per day.

The theoretical alkalinity demand during nitrification is 7.14 times the influent ammonia. When there is not enough alkalinity to complete the conversion of nitrogen pollution into harmless nitrogen (a process called nitrification) then it is necessary to add a safe and effective source of alkalinity such as FloMag^® H magnesium hydroxide slurry. Sufficient alkalinity will buffer the pH at a healthy 7.0-7.2 level, and allow efficient elimination of nitrogen pollution.

The theoretical alkalinity demand value is a minimum — not all alkalinity is "bio-available". The operator must meter additional alkalinity to maintain the operational pH near-neutral, to account for influent ammonia variation, to compensate for the presence of chemicals that consume alkalinity, to prevent the growth of smelly sulfur bacteria, and to maintain residual treated alkalinity at 70-80 mg/l as CaCO₃. As a rule of thumb, alkalinity levels should be at least eight (8) times the concentration of influent ammonia in wastewater. This value may be higher for untreated wastewater with higher-than-usual influent ammonia concentrations. The required volume of alkalinity to add is calculated by dividing the daily bio-available alkalinity demand by the alkalinity provided per gallon obtained from the source of alkalinity.

FloMag^® H magnesium hydroxide slurry contains 13.38 pounds of carbonate alkalinity per gallon. Sodium hydroxide (caustic soda) contains less alkalinity per volume and per dry pound than FloMag^® H magnesium hydroxide slurry.

FloMag^® H magnesium hydroxide slurry is safe for personnel to handle and will not harm aerobic or anaerobic bacteria if overdosed. In contrast, caustic soda is corrosive, hazardous to personnel to handle, and can be lethal to bacteria if too much caustic soda is added in error. Remember to compare safety, sludge volume, and other important magnesia slurry advantages. Since each process is a bit different, consider evaluating a FloMag^® H trial run at your facility. Martin Marietta Magnesia Specialties sales staff will assist perspective customers in the completion of a site survey form, which allows the applications engineers to develop the right product application equipment for your site. Please Contact Us for more information.