What effect do caustic soda, soda ash, and lime have on pH levels?

Caustic soda, soda ash, and lime are all substances that act as alkaline agents when added to water. Their primary effect on pH levels is to increase the pH.

Caustic soda (sodium hydroxide) is a strong base that significantly raises the pH of water when dissolved. Soda ash (sodium carbonate) is a weaker base but still contributes to higher pH levels and can enhance alkalinity, which means it can effectively increase the pH by reacting with acids in the water. Lime (calcium hydroxide) also raises pH by providing hydroxide ions that neutralize acids in the water, leading to an increase in overall pH.

The fundamental role of these substances in water treatment processes often involves adjusting pH to optimize conditions for disinfection, enhance coagulation, or improve the efficiency of other treatment processes. Therefore, these agents are commonly used to achieve higher pH levels, making option 'B' the correct response.