Turbidity:In simple words turbidity is basically the cloudiness ormuddiness of water.
Turbidity occur due to suspended particles, bacteria,dissolved organic substances and suspended clay particles. In case of textile effluent,the presence of suspended solids either in dissolved or in undissolved statecan caused turbidity. Untreated water remains turbid for a longer period asfine particle takes days or weeks to settle down.Coagulation:Coagulation is a technique of converting smaller sizeparticle in to a larger one by sticking them together chemically. Watercharacteristics is concerned as the coagulants used either work efficiently ornot depending upon the effluent water, mainly used coagulants are alum, ferricchloride, poly aluminium chloride, the process is carried out through jar testalong with correct dosage through feed pump calibration. The effluent water isadded after the coagulant mixed for some time with static mixer, proper mixingis required for coagulation as the process kicks start as soon as the chemicalsare added. The effluent can either mixed through motorised paddle or it maysplash in to the jar.
Flocculation:Flocculation is a three-stage process and activates whenparticulates start sticking together more clearly. First stage is fastest ascompare to the second and third stage. The process uses motorised paddle formixing sometimes in opposite direction to resist the breakdown of heavyparticulates during stirring. During sedimentation heavy particulates aresettle down at the bottom. The process is proceeding through filtration.
At theend of flocculation daily turbidity reading is taken.Dye characteristics:Capacity to absorb light invisible region is a common property for all dyes. The reductive cleavage of azolinkages can result in the creation of toxic amines in the effluent.Anthraquinone-based dyes consist of bonded aromatic structures and are moreresilient to degradation.
Basic dyes are applied widely in small-scaleindustries such as textiles and carpets 3,4. The most challenging are anionicdyes because they are intensely coloured, water-soluble, and show acidicproperties. dyes Ionic character chromophore In aqueous solution acid anionic azo groups or anthraquinones. Net negative charge (sulphonate and/or carboxylic group) reactive anionic azo groups or anthraquinones. Net negative charge (sulphonate and/or carboxylic group) direct anionic azo groups or anthraquinones. Net negative charge (sulphonate and/or carboxylic group) basic cationic Net positive charge dispersed non-ionic azo groups or anthraquinones.
Water soluble reactive dyes:Reactive dyes are widely used in textile industries becauseod wide range of wet fastness, colour range. Straightforward application and minimumenergy consumption. The structure of reactive dye molecule consists of fourcharacteristics:· Chromophoric group· The reactive group· Bridging group· Solubilising group They all contribute towards the substantivity for cellulosefibre.
Reactive group can react through nucleophilic substitution ornucleophilic addition reaction. During high alkaline condition in reactive dyesa hydrolysed reaction take place which result in non-fibre reactive form, whichcannot covalently bond with the substrate and end up in dyebath effluent.Adsorption:Adsorption is a separation process and a technique for waterrefinement application such as decolourisation from dye waste water.Decolourisation is done by ion exchange and adsorption and is affected by manyphysio-chemical factors that includes particle size, pH, Temperature, contacttime, sorbent surface area and sorbent interaction. The low-cost absorbent istypically as peat, bentonite, steelplant slag, flyash, china clay, maize cob, wood shavings and silica for colour removal. Theseabsorbents are used in large amount because of their low absorption capacities.
Mechanism:The term adsorption expresses aprocedure where in a material is concentrated at a solid surface from itsliquid or gaseous environments. Two types of adsorption techniques are there: Physsorption “If the attraction between the solid surface and the adsorbedmolecules is physical in nature, the adsorption is referred to as physicaladsorption wherein the attractive forces are weak van der Waals forces,resulting in reversible adsorption”. Chemisorption “has higher strength ofchemical bonding between adsorbed molecules and the solid surface, making itdifficult toremove the chemisorbed species from the solid surface.”Adsorption technique is used toremove such pollutants that are not easily biodegradable. the processcompletion take place in three steps:1) diffusion of dye molecules through the solutionon to the surface of the adsorbent. (affected by dye concentration andagitation)2) adsorption of dye molecules on the surface ofthe material through molecular interactions (dependent on the nature of dyemolecule)3) diffusion of dye molecules from the surface tothe interior of the adsorbent material.