White Paper: The Role Of Alkalinity In Aerobic Wastewater Treatment Plants: Magnesium Hydroxide vs. Caustic Soda
Downloads:•White Paper: The Role Of Alkalinity In Aerobic Wastewater Treatment Plants: Magnesium Hydroxide vs. Caustic Soda
Modern day wastewater treatment plants must use a variety of physical, chemical and biological processes to meet effluent treatment guidelines. During the course of treatment these plants consume a variety of different chemicals. In some treatment plants an alkali is used to provide the alkalinity required to maintain effective biological activity and for pH control. This paper will discuss the role that alkalis play in wastewater treatment. Therefore, this report will have three sections. The first section defines the term alkalinity, what it is and what it is not. The second section examines why alkali chemicals are used for wastewater treatment. The third and final part presents facts as to why magnesium hydroxide is the alkali of choice for these applications.
Alkalinity, Definition and Composition
Alkalinity can be defined as the ability of a water to neutralize acid or to absorb hydrogen ions. It is the sum of all acid neutralizing bases in the water. In municipal and industrial wastewater there are many factors which contribute alkalinity. Factors which contribute to alkalinity include the type of dissolved inorganic and organic compounds present in the water, the amount of suspended organic matter in the water, whether the water is strongly or weakly buffered, the presence or absence of free hydroxyl alkalinity, the amount of bicarbonate in the water, the bicarbonate to dissolved CO2 ratio and is indirectly correlated to the amount of dissolved solids in the water.
The pH is the measure of the hydrogen ion concentration of the water but it does not determine how many hydrogen ions that water can absorb. pH is a useful indicator of the transition between carbonate and bicarbonate alkalinity. pH is also used to determine the point at which alkalinity stops and free acidity begins. The pH of a water serves as a guide to the types of alkalinity present in the water but is unrelated to the alkalinity content of a water.
The bacteria and other biological entities which play an active role in wastewater treatment are most effective at a neutral to slightly alkaline pH of 7 to 8. In order to maintain these optimal pH conditions for biological activity there must be sufficient alkalinity present in the wastewater to neutralize acids generated by the active biomass during waste treatment. This ability to maintain the proper pH in the wastewater as it undergoes treatment is the reason why alkalinity is so important to the wastewater industry.
Downloads:
•White Paper: The Role Of Alkalinity In Aerobic Wastewater Treatment Plants: Magnesium Hydroxide vs. Caustic Soda