DISINFECTION OF TREATED SEWAGE AND SAFE DISPOSAL OF EFFLUENT By -Er. G.Krishnan, M.E. (PH),Executive Engineer / TWAD Board Welcome

INTRODUCTION: COMMON TYPE OF CHLORINE COMPOUND USED DISINFECTION OF TREATED SEWAGE AND SAFE DISPOSAL OF EFFLUENT

CHEMISTRY OF CHLORINE REACTION IN WATERHydrolysis may be defined asCl2 + H20 HOCl + H+ Cl- (Hypochlorus acid)Ionization may be defined asHOCl H+ OCl- (Hypochlorite)

REACTION OF HOCL WITH AMMONIANH3 + HOCl NH2 Cl + H2O (Mono Chloramine)

NH2C1 + HOCl NHCl2 + H2O] (Dichloramine)

NHCl2 + HOCl NCl3 + H2O (Nitrogen Trichloride)

BREAKPOINT CHLORINATIONChlorine added, mg/L

REACTIONS ACCOUNT FOR THE APPEARANCE OF GASES AND DISAPPEARANCE OF CHLORAMINESNH2 C1+NH Cl2 +HOCl N20+4HCl

4 NH2 Cl + 3 Cl2 + H2- N2+N20+10HCl

2 NH2 Cl + HOCl N2+H20+3HCL

NH2 Cl + NHCl 2 N2+3HCl

TOXICITY OF CHLORINE RESIDUALS : Dechlorination with sulfur dioxide (S02) Reaction with Chlorine:S02 + HOCl + H20 Cl- + SO-4+ 3H+

Reaction with chloramine:

S02+NH2Cl+2H2O Cl-+SO-4 +NH+4 +2H+

USES IN SEWAGE TREATMENT

USES IN SEWAGE TREATMENT Cont..

USES IN SEWAGE TREATMENT Cont..

DOSAGES:

CHLORINE COMPOUND SUPPLY FORMCHLORINE CONTAINERS SAFTY MEASURECALCIUM HYPOCHLORITE

SODIUM HYPOCHLORITE

CHLORINE EQUIPMENT AND DOSAGE CONTROL FEEDERS Schematic flow diagram for chlorination/ dechlorination Using a chlorine injector system

DOSAGE CONTROL By manual control the Operator changes the feed rate to suit conditions. The required dosage is determined by measuring the residual after 15 minutes of contact time and adjusting the dosage to obtain a residual of 0.5mg/LUse of a program control that charges the feed rate to follow a pre selected pattern. It is most economical with automatic controlA parshall flume or flow rube is used to pace the chlorine flow rate to the waste water flow rateAn automatic analyzer with signal transmitter and recorder is used to control Chlorine dosage.A compound system of 3rd and 4th to control the Chlorine dosage.

CHLORINATION FACILITIES: Method of Chlorine addition and provision for mixingThe design of Chlorine contact basin designMaintenance of solid transport velocityProvision for by passing the chamberOutlet control MPN measurement

INJECTION AND INITIAL MIXING:

INJECTION AND INITIAL MIXING cont.

INJECTION AND INITIAL MIXING cont.

CHLORINE CONTACT BASINS

Typical chlorine contact basin with removable baffles

Photograph of empty Chlorine contact basin designed with guide vanes.

MAINTENANCE OF SOLIDS TRASPORT VELOCITYCHLORINATION BASIN BYPASSOUTLET CONTROL AND MPN MEASUREMENT

Thank YouBy -Er. G.KRISHNAN, M.E. (PH),Executive Engineer / TWAD Board