How can a low pH be raised?

Raising a low pH typically involves adding a substance that is alkaline or basic, which can neutralize acidity and bring the pH level up towards a more neutral range. Sodium hydroxide is a strong base that effectively increases the pH when added to a solution. Upon dissolution in water, sodium hydroxide dissociates into sodium ions and hydroxide ions, which contribute to the increase in hydroxide concentration, thus raising the pH level.

The effectiveness of sodium hydroxide in adjusting pH makes it a common choice in wastewater treatment processes where pH control is crucial for both regulatory compliance and optimal treatment performance. When dealing with acidic wastewater, applying sodium hydroxide is a direct method to neutralize the acidity.

On the other hand, substances like sodium chloride would not affect the pH significantly, as it does not possess alkaline properties. Similarly, phosphoric acid would further lower the pH, and calcium hydroxide, while also capable of raising pH, was not identified as the best direct answer in this context. Therefore, the use of sodium hydroxide for effectively raising low pH levels aligns perfectly with the requirements of wastewater treatment procedures.