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Municipal Water Treatment (PAC)

The process flow diagram illustrates an municipal water treatment plant that is used for the removal of taste and odour compounds.

In certain regions the treatment of the water intended for potable purposes is not necessary at all times during the year. The presence of taste, odour and toxins is dependent largely on the biological action in areas where lake or reservoir supply is common. It is therefore often more cost effective to use temporary or intermittent dosing of activated carbon into the water only during times when treatment is required.

Bulk PAC fully automated dosing equipment from silos

In these instances, the use of Powdered Activated Carbon (PAC) is preferred, as no costly fixed bed filtration equipment is required. The PAC can be dosed directly to existing flocculent tanks at a prescribed rate to achieve the level of removal of taste, odour and toxins as required. Following dosing of PAC the activated carbon is removed as part of the flocculation process, or subsequently filtered mechanically. The water is then disinfected for supply to the distribution network.

Process Water Treatment

The process flow diagram illustrates a water treatment plant used for the removal of creosote and pesticides from the liquid phase in a timber treatment facility. A storage tank is used for smoothing the flow, from where the water is pumped into a chemical dosing system for pH adjustment. At this stage, ferric sulphate is added to form a precipitate with suspended solids, which is subsequently flocculated by the addition of polyelectrolyte.

Water is then pumped through series operated sand filters, which provide the final stage of suspended solids removal and protect the granular activated carbon (GAC) filters from particulate contamination. Series operated GAC filters are then used to remove the dissolved creosote and pesticides from the water. To ensure compliance with specification levels, the water is sampled and analysed after the first GAC filter. The second GAC filter acts as a guard bed.

Process water treatment plant at Calders and Grandidge Ltd

The unique feature of this adsorption system is the use of dual GAC media beds. By careful selection of the GAC it was possible to install two types of GAC, which function as discrete layers. The top portion of the adsorber was filled with Filtracarb CC60/1240, which acts as a sacrificial layer, removing bulky organic compounds. Filtracarb SX5 was installed under this layer, providing a highly retentive media for maximum adsorption efficiency.

Municipal Water Treatment (GAC)

The process flow diagram illustrates a municipal water treatment plant that is used for the removal of taste and odour compounds. Water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate material. Dissolved air is injected under pressure into the basin through special nozzles. This creates microbubbles which become attached to the suspended solids, causing them to float. The result is a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique.

City of Oulu (Finland)- municipal water treatment plant

Ozone is produced on site by passing high tension, high frequency electrical discharges through air in specially designed equipment. Ozone is injected into the water to provide a powerful bactericidal action and to break down the natural humic compounds that are the cause of the taste and odour problem. 　 The water then enters a rapid gravity filtration system filled with Filtracarb FY5, which is used to adsorb the compounds resulting from the ozone treatment. Filtracarb FY5 was selected due to its high surface area and retentive pore structure, smaller molecules.