Waste water treatment

Many different forms of wastewater occur in a power plant which must be subjected to treatment before being discharged. The display shows the classification of the wastewater in different groups:

	Group I: chemically polluted wastewaters
	Group II: wastewaters with high solids contents
	Group III: oil freighted wastewaters

This wastewater occur both continuously as well as sporadically.

The wastewater of Group I is initially neutralized before it is subjected to a flocculation procedure. Most of the solids are separated in a sedimentation plant, a portion is returned to the flocculation stage in the form of contact sludge. The rest is supplied to the process or to the detoxification stage.  The clean water can, if required, be subjected to a detoxification treatment process, for example with an oxidation material. The partially cleaned water of the three groups is routed to a baffle plate separator after flocculation and settling in which the adsorption and settling of the remaining solids particles is undertaken. The resulting sludge is concentrated in the coagulator to be drained in a filter press. Because of the intake of the diverse wastewater into independent collecting and/or buffer vessels and the assignment to the different treatment stages, an almost consistent load distribution to the different treatment stages is attained. The possibility of the use of different chemicals, the extension with additional chemicals and systems in the process allows for individual adaptation to the wastewater.

Sunstantial wastewater quantities result during the fluegas desulpherisation process. Most desulpherisation plants operate with the lime/limestone wash process in which industrially usuable gypsum is the main product. In order to achieve a clean end product, the strongly acidic components of the fluegas, in particular hydrogen chloride and fluoride, are removed from the fluegas stream by a connected washer before the fluegas goes through the actual desulphurisation plant. The prewash water is relatively acidic and contains alkalies, alkali salts as well as heavy metals. These acidic wastewaters are mixed with the wastewater in the lime washing plant. In this process, other components from  the lime also go into the wastewater.  The wastewater treatment fullfills the following tasks:

	neutralises the acids
	separates the solids in the wastewater
	reduces the concentration of heavy metals
	reduces the concentration of saturated gypsum
	reduces the organic freight (e.g. amino acids)

Of particular importance is an excellent flocculation sedimentation and separation of the solids in order to suffice the requirements for the discharge. These tasks can be undertaken with single/ double stage fluegas desulpherisation plants. The picture shows a two stage plant. The fluegas desulpherization plant is a separate system. The cleaned wastewater is supplied to the central wastewater treatment unit in the power plant.