0 Wastewater treatment

We may organize water treatment technologies into three general areas: Physical Methods, Chemical Methods, and Energy Intensive Methods. Physical methods of wastewater treatment represent a body of technologies that we refer largely to as solid-liquid separations techniques, of which filtration plays a dominant role. Filtration technology can be broken into two general categories - conventional and non-conventional. This technology is an integral component of drinking water and wastewater treatment applications. It is, however, but one unit process within a modern water treatment plant scheme, whereby there are a multitude of equipment and technology options to select from depending upon the ultimate goals of treatment. To understand the role of filtration, it is important to make distinctions not only with the other technologies employed in the cleaning and purification of industrial and municipal waters, but also with the objectives of different unit processes.
Chemical methods of treatment rely upon the chemical interactions of the contaminants we wish to remove from water, and the application of chemicals that either aid in the separation of contaminants from water, or assist in the destruction or neutralisation of harmful effects associated with contaminants. Chemical treatment methods are applied both as stand-alone technologies, and as an integral part of the treatment process with physical methods.
Among the energy intensive technologies, thermal methods have a dual role in water treatment applications. They can be applied as a means of sterilisation, thus providing high quality drinking water, and/or these technologies can be applied to the processing of the solid wastes or sludge, generated from water treatment applications. In the latter cases, thermal methods can be applied in essentially the same manner as they are applied to conditioning water, namely to sterilize sludge contaminated with organic contaminants, and/or these technologies can be applied to volume reduction. Volume reduction is a key step in water treatment operations, because ultimately there is a tradeoff between polluted water and hazardous solid waste. Energy intensive technologies include electrochemical techniques, which by and large are applied to drinking water applications. They represent both sterilization and conditioning of water to achieve a palatable quality.
All three of these technology groups can be combined in water treatment, or they may be used in select combinations depending upon the objectives of water treatment. Among each of the general technology classes, there is a range of both hardware and individual technologies that one may select from.
The selection of not only the proper unit process and hardware from within each technology group, but the optimum combinations of hardware and unit processes from the four groups depends upon such factors as:
1.How clean the final water effluent from our plant must be:
2.The quantities and nature of the influent water we need to treat;
3.The physical and chemical properties of the pollutants we need to remove or render neutral in the effluent water;
4.The physical, chemical and thermodynamic properties of the solid wastes generated from treating water; and
The cost of treating water, including the cost of treating, processing and finding a home for the solid wastes. To understand this better, let us step back and start from a very fundamental viewpoint. All processes are comprised of a number of unit processes, which are in turn made up of unit operations.
Unit processes are distinct stages of a manufacturing operation. They each focus on one stage in a series of stages, successfully bringing a product to its final form. In this regard, a wastewater treatment plant, whether industrial, a municipal wastewater treatment facility, or a drilling water purification plant, is no different than, say, a synthetic rubber manufacturing plant or an oil refinery.