For those interested in the technical aspects of the treatment of water, a conventional municipal water treatment system comprises the following:

Conventional surface water treatment plants are utilised throughout South Africa and Africa and typically consist of numerous phases in the treatment process; Water Collection, Screening and Straining, Chemical Addition, Coagulation and Flocculation, Sedimentation and Clarification, Filtration, Disinfection, Storage, and Distribution.

Collection: The most common water source for a municipal water treatment plant is a local river or dam. The water must be transferred from the source to the water treatment plant wherever it is located. Often, a series of pumps and pipelines transport the water to the treatment plant. Large pumps are required at the water collection sites to transfer the water to the treatment facility from lower-lying catchment areas. Treatment facilities are often engineered to utilise gravity water flow as much as possible to reduce overall pumping costs.

Many water treatment plants utilise water from more than one source to ensure adequate supply and redundancy during variability periods. 

Blending groundwater with surface water is often used to improve the quality of the final product. Still, this is not possible in certain areas due to the contaminant concentrations in the feed water.

Screening and Straining: Surface water sources such as lakes, rivers, and reservoirs, contain varying quantities of suspended and dissolved materials. This material may include turbidity, colour, taste, odour, microorganisms, fish, plants, trees, waste, and occaisonally untreated effluent. The material may be organic or inorganic, suspended or dissolved, inert or biologically active, and vary in size from colloidal to a tree trunk. Some of these larger items can impede equipment in the treatment process. The first process in conventional water treatment is to screen, strain or separate the larger items and debris from the source water. This is often achieved by using a large metal screen, often called a bar- screen, placed in front of the water source intake. Large items are trapped on the screen as the water passes through it.

Chemical Addition: The pre-screened water pumped to the treatment plant is combined with chemicals to allow the suspended particles floating in the water to clump together to form heavier and larger particles. This clumping is often referred to as floc. The chemicals react with the natural alkalinity in raw water to form an insoluble solid. These chemicals are referred to as coagulants and flocculants. 

Coagulation and Flocculation: A rapid mixing unit is usually used to add the coagulant to the water. Rapid mixing provides a rapid and thorough mixing of chemicals and water. The rapid water mixing is allowed slow to enable the suspended matter in the water to form floc and increase in size. The continued mixing is gentle enough to allow the floc to continue growing and gain mass. The mixed water is sent to clarifiers to allow the large floc mass to settle. The process of adding chemicals to aid the suspended material to clump into larger particles is called flocculation or coagulation. 

Sedimentation and Clarification: After the flocculation process is complete, the water then passes to the clarifier or settler where the water flows from the clarifier’s centre to the weir at the perimeter of the clarifiers or settlers. As the water makes its way towards the weir, the large floc particles are allowed to settle at the bottom of the clarifier. A rake continuously scrapes the bottom of the clarifier so that the settled floc reports to the centre of the unit. Pumps are used to draw the settled “sludge” out of the clarifier and send it to a sedimentation pond. The water that passes over the weir is collected and transferred to the filter process. Clarification is used to significantly reduce the solids in the source water and subsequent need for backwash of the filtration system.

Filtration: Clarified water enters the filters from the top. Gravity allows the water to percolate through the filters. The water is collected in a drainage system at the bottom of the unit. There are many different types of media used in filters. The most common being sand and gravel. Many conventional plants are now using granular activated carbon as the media of choice. It provides excellent mechanical filtration of particulate matter and removes organic compounds that can cause taste and odour problems.

Disinfection: Water that has passed through the filtration process is clear and clean to the visible eye. There may still be bacteria and viruses remaining which need to be destroyed through disinfection. The most common disinfection process used is chlorination. Chlorine comes in many different forms, including chlorine gas (the most common), chlorine dioxide and hypochlorite. Whichever method is used, chlorine is added to the water in a quantity to ensure that most, if not all, viruses and bacteria are destroyed. Sufficient chlorine must be added to ensure thorough disinfection of the water but avoid excesses that can cause taste and odour problems when delivered to the consumer.

Storage: After the disinfection process is complete, the water is stored. Water storage usually occurs in underground storage tanks or in elevated storage tanks that are visible around most towns and cities. Typically there should be an ample supply of water available in the event of emergencies. These events could include power outages, fires and floods.

Distribution: The stored water is pumped through underground pipelines all over towns and cities in what is typically referred to as a distribution network. The distribution network consists of large water pumps at the treatment plant, overhead water storage tanks for gravity-fed systems, large pipelines, smaller pipelines, fire hydrants, valves, and water meters at the user’s property.

NuWater’s, water treatment solutions can replace or augment one or more of the above mentioned processes which may no longer be adequate or fit for purpose due to redundancy or demand. NuWater will ensure that existing infrastructure is enhanced so as to achieve the highest efficiency, reliability, flexibility and production of potable water from almost any source.