The Link Between Alkalinity and Wastewater Operations

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The Link Between Alkalinity and Wastewater Operations

Alkalinity is a common water analysis parameter described as the acid-neutralizing and pH buffering capacity of a solution. Maintaining a residual alkalinity concentration of 70 – 80 mg/L ensures that high quality floc is produced, and the pH of aeration tanks remain neutral; promoting a stable environment for biological activity1.

Hydroxides (OH), carbonates (CO32-), and bicarbonates (HCO3) are the primary contributors to the pH buffering capacity of a solution2. Buffering capacity can be characterized by the absorption of positively charged hydrogen ions by negatively charged HCO3 and CO32- molecules. This results in a shift in the equilibrium without causing a significant change in the pH3. Additionally, carbonate alkalinity is consumed during the nitrification step of the activated sludge process, where nitrification rates will reduce significantly below a pH of 6.8. The activate sludge process results in an overall acidic environment, requiring constant monitoring and maintenance of pH levels, optimally between a pH of 7.0 -7.41.

Total alkalinity is calculated as the sum of the concentrations of OH, CO32-, and HCO3 in a solution, and expressed as mg of CaCO3/L2. In addition to facilitating and promoting biological activity in wastewater operations, alkalinity analysis is used to monitor water for drinking, surface, and saline waters, swimming pools, heating and cooling, food and beverage cleaning systems, and in soil and agriculture.

MANTECH specializes in automated speciated alkalinity analysis from as little as 10mL of sample. Total analysis time is typically <4 minutes including automated pipetting, analysis and rinsing. Additional parameters such as pH, conductivity and Chemical Oxygen Demand (COD) can be added in both laboratory and online system configurations. Visit the MT series product page for more information. Contact a MANTECH representative today to learn how a MANTECH system can work for you.

For more information on the influence of alkalinity on plant operations, read the OPS Challenge Laboratory Event for Alkalinity Profiling in Wastewater Operations.

1 Alkalinity Profiling in Wastewater Operations: OPS Challenge Laboratory Event 2015. 4 July 2018. https://www.rmwea.org/docs/Alkalinity_Profiling_in_Wastewater_Operations_White_Paper_OPS_2015_ED_1.20.15.pdf

2 Smith, Roy K.  1999.  Handbook of Environmental Analysis: 4th Edition.  Genium Publishing, New York, pg 235-236.

3 Acid Mine Drainage: Alkalinity.  Exploring the Environment: Water Quality. Wheeling Jesuit University. 5 Feb 2002. http://www.cotf.edu/ete/modules/waterq/wqalkalinity.html.

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