pH adjustment chemicals are common chemicals in water and waste water treatment plants.

Some commonly known ones are :

  • Caustic Soda / Lye / Sodium Hydroxide
  • Soda Ash /Sodium Carbonate
  • Hydrated Lime / Calcium Hydroxide
  • Sulphuric Acid
  • Hydrocholic Acid.
  • Sodium Bisulphate

What are the typical uses of pH adjustment chemicals?

You are most probably using the chemicals above at any step below:

Chemical Processes of Waste Water Treatment Plant

A typical chemical treatment waste water treatment step starts with pH adjustment, followed by coagulation and flocculation. In the first tank, i.e. pH adjustment, an online pH sensor will measure the pH value of the waste water before the pump does its work to dispense the correct amount of pH adjustment chemical.

This step is important to ensure that wastewater is having the correct pH (typically between 6-9) to ensure coagulation and flocculation will take place successfully.

If this step is not done well, you may not be able to precipitate completely all dissolved solids in the waste water, including heavy metals like Zinc.

Chlorine Disinfection of Water

Chlorine is a relatively cheaper disinfection chemical that is used widely in many places, such as in swimming pools, and drinking water systems. Chlorination works optimally at pH range of 5-7. At pH exceeding 7, more OCI- and less Hypochlorous acid HOCl ( an active sanitizing agent) is generated, hence reducing the effectiveness of chlorination.

Before Distributing Water to Public/ Industrial Uses

The acceptable pH range for drinking water in Malaysia is 6.5-9. Anything out of this range will call for pH adjustment. Moreover, water with a pH level below 6.5 can leach metals and corrode pipes, making it dangerous to health if consumed, due to presence of heavy metals like lead, iron, manganese, zinc and copper.

On the other spectrum, highly alkaline drinking water will make your drink tastes bitter.

To Maintain Biological Waste Water Treatment Process

Most biological wastewater treatment plants work the best at pH range of 7-8. Otherwise, bacteria will not survive well.

However, since these systems are unable to handle “shock loads” well, you need to take extra consideration in chemical and method selection. Buffering capacity is the key point here.

Selecting the suitable pH adjustment chemicals

Most industries produce wastewater which is acidic in profile.

There are some exceptions, for example, cement factories and oil refineries produce alkaline waste water.

In general, all pH adjustment chemicals listed earlier have their advantages and disadvantages.

For example, caustic soda (sodium hydroxide) is widely used for its high solubility, effectiveness, and competitive pricing, but it is a strong base and is not good as a buffer solution.

Its closest alternative is probably soda ash (sodium carbonate) – equally soluble but needs a higher usage and cost to match the performance of caustic soda.

To lower the PH of water, usually acids such as sulphuric and hydrochloric acids are used. Being strong acids, both are posing hazards to our health, and require extra care when handling.

If you need assistance in water pH adjustment, please do not hesitate to contact us.  We have solid, proven experience in dealing with water/ waste water from different industries, for example, food processing, chicken slaughtering, rubber gloves, paper mills etc.