Water quality treatment processes

Determination of noninorganic surfactants (NS) in environmental water samples or in samples relevant to environmental water quality (sewage, processing liquors in sewage treatment plants, and treated sewage) is difficult because of the complexity of the matrix, the multicomponent nature of the NS mixture in the aquatic environment, and the limited stability of samples.133... 

Treated Water Quality. Predicted analyses of a typical raw water treated by various lime and lime—soda softening processes are presented in Table 3. Treatment by lime converts the sodium bicarbonate in the raw water to sodium carbonate as follows ... 

In many cases, the quality of a stream or another water source can be adequately improved by removing more BOD or suspended solids. In other iastances, the effluent is prepared for groundwater recharge which may require only the removal of nutrient. A classification of wastewater treatment processes is given ia Table 3. Table 4 summarizes water quality criteria for various iadustrial uses (10). 

Where the feed contains a large proportion of treated water, softening is a minimum requirement and the raw water quality dictates whether a more sophisticated form of external treatment would be preferable. If the water has a high alkalinity it calls for de-alkalization and base exchange. De-ionization is the ideal water treatment, but is usually avoided if possible because of its cost and use of corrosive chemicals. Membrane processes giving partial de-ionization are not normally installed at present, but are certain to become important in the future. 

Synthetic resins are extremely widely used, both pre-boiler and postboiler. Pre-boiler, they are employed for basic MU water treatment (e.g., softening) and various higher quality purification processes (e.g. dealkalization and demineralization). Post-boiler applications are for condensate polishing. 

Like water temperature, water quality downstream from reservoirs depends on the hydrodynamic processes that take place in the reservoirs. In the case of the Ebro River, the effect of the reservoir of Mequinensa on water quality was studied by Roura [46]. According to her results, this reservoir acted as a treatment plant that improved the quality of the river water. Also, the hydrodynamics of the reservoir depends on upstream water temperature, discharge and meteorological variables. Such forcing parameters change over the years and, consequently, the water quality... 

Due to the partial to complete resistance of many pesticides to biodegradation during the wastewater treatment processes, these compounds can escape elimination in WWTPs and enter into the aquatic environment. As a consequence, their evaluation represents an important objective in the efficiency of WWTPs and water quality. 

Each type of technique can be applied in several modifications. Microbiological degradation processes offer the possibility to purify wastewater streams which contain a wide range of organic pollutants. In contrast, physical/chemical techniques are much more specific. The quality of the purified water regarding residual amounts of soluble organic pollutants, and colloidal and suspended particle pollutants, strongly depends on the type of treatment process and the applied treatment conditions. Very often a combination of different types of treatment techniques is necessary to satisfy the effluent quality required (for example a combination of anaerobic and aerobic treatment). 

As a first approach it is assumed that an industrial closed water loop focuses on the production of one type of process water of a constant water quality and temperature. After this process water has been polluted and has become a wastewater, it will be treated to the required quality and will be used again as process water. In fact this is the simplest form of a closed loop water system. We will discuss this situation first. The first step in the design of such a simple closed loop water system is to consider the type of separate treatment steps and the sequence of these treatment steps which have to be applied on a wastewater stream that contains large amounts of easily biodegradable soluble pollutants in addition to non-biodegradable soluble organic and inorganic pollutants and suspended and colloidal particulate... 

The starting point in the development and designing of a closed water loop system is an inventory of the amounts and the quality of the process and transport water flows which are needed for the various steps in the production process. Each production step where process or transport water is involved causes a certain amount of wastewater. The pollution of this water is strongly dependent on the process step. The selection of separate treatment steps which, together, comprise a closed loop water system is complex. As already mentioned, various complete treatment scenarios can be developed and designed to satisfy the requirements set for process and transport water and treatment of wastewater. A technical and economic evaluation, in combination with environmental sustainability assessment, is necessary to determine the treatment system which is most appropriate. 

---