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Water Treatment Plants – the Different Types

Water Treatment Plants in Africa

A water treatment plant is a facility where water is treated to make it acceptable for the end-user, or for environmentally safe discharge back into the water cycle. The most common type of wastewater treatment plant is a municipal sewage treatment plant. The number of industrial wastewater treatment plants are increasing, mainly due to mounting environmental pressures and efforts to reduce water costs and availability of water .

Various processes are involved in this exercise, which can include sedimentation, filtration, chlorination, disinfection and chemical stabilisation. Constructed wetlands are increasingly being used as a good alternative to built processes.

To Begin with Wastewater Treatment:

In a nutshell, you will need to start by testing the wastewater in order to find out what is in the water and how much. The water is then treated to make it safe for reuse.

Government regulations specify the allowable limits / amounts of various substances that can be present in the water before it may be discharged into a water resource. These substances start with the basics of pH, Electrical Conductivity, Faecal Coliforms and are then expanded to include more substances, such as nitrates and ammonia. View Current Regulations for Waste Water Monitoring.

A modern photometer is an electronic instrument that can be used to measure most of the substances in water. This can be done by the wastewater treatment plant itself, or contracted out to a water testing laboratory. A coliforms / e.coli testing kit will be required to measure the microbiological Faecal Coliforms count.

A Flow Meter will also be required to calculate the volume of water.

In order to make the waste water reusable, it is treated to remove these physical, chemical and biological pollutants and make it safe for reuse or for drinking.

An excellent resource for what to do to treat the water once you know what’s in it is the Drinking Water Treatability Database. (This is like a professional gold mine of info for anyone involved with water treatment. It is very extensive and managed by the US EPA.)

1. Surface Water Treatment Plant:

A surface water treatment process is typically used to make surface water fit for municipal applications. Suspended impurities, colloidal matter and organic components are removed through processes like sedimentation, aeration, screening, disinfection and sand filtration.

A smaller municipal water treatment plant. Source: DWA

2. Reverse Osmosis Water Treatment:

This is another popular facility designed by water treatment plant manufacturers. High quality water for domestic use is produced. Bear in mind that membrane modules have a limited life span and need to be replaced periodically. Reverse osmosis is a higher cost option that requires expert maintenance.

Pharmaceutical Reverse osmosis plant

3. Seawater Treatment Plant:

Seawater is treated to remove dissolved minerals and salts at a seawater treatment plant. Desalination, membrane separation, vacuum freezing and many such processes are employed at these plants. Saudi Arabia and the USA are the two countries with most number of seawater desalination plants.

In South Africa, we have a Seawater Desalination Plant at Mossel Bay

4. Ozone Based Water Plant:

These plants use ozone for water purification and are useful to treat pool water or water present in cooling towers. Ozone is an excellent disinfectant for variety of microorganisms, including cryptosporidium and protozoan parasites. The main advantage of this type of plant is that it doesn’t require adding any chemical to the water. Ozone is often used in combination with another treatment, as

Midvaal ozone Water Treatment Works

5. Bottled Water Treatment:

The popularity of bottled drinking water is increasing with passing time. The water is collected at the source, treated and packed in bottles that are supplied to the market. A bottled water plant is installed near the source to make water treating easy and economical.

Aquabella water bottling plant near Paarl in South Africa

6. Containerised Water Treatment Plant:

To make pollutant-free water available in remote areas, the containerised treatment plant for water is considered as a suitable option. A single unit arrangement is used in this category of treatment equipment. They are frequently used in small rural environments, remote mining areas or recreational areas.

A portable water treatment facility in a container. Source: DWA

7. Constructed Wetlands Water Treatment:

Relatively inexpensive but more labour intensive, constructed wetlands are an ideal solution for water treatment of effluent in many agricultural industries. The water passes over a bark filter, through gravel, stones and reeds and into a reservoir or pond. Environmental specialists are able to construct and advise on maintainance of constructed wetlands.

Natural Water Treatment at Spier in the Cape Winelands

DOWNLOAD FREE practical DWA Book on Water Treatment that discusses the various options and how to put a plan in place.

 

Article updated April 2016

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