The Reuse Of Water Treatment Sludge As A Coagulant For Post-

treatment Of UASB Reactor Treating Urban Waste Water

Abhilash T Nair, M Mansoor Ahammed

Aravind E SCE13M022

Introduction• UASB • WTS • Effluent from UASB does not meet disposal standards • WTS (water treatment sludge) have adverse effect on

environment • Feasibility of reusing aluminium-WTS as a coagulant

for post-treatment of UASB effluent treating urban waste water .

• RSM(response surface methodology) used to optimise coagulation process .

• Variables –WTS dose ,initial pH and PACL (poly aluminium chloride )

• Responses –COD removal and turbidity removal .

Methodology • Aluminium Sludge –from Katargam WTP at surat, India

o treat water from Tapi river o PACL as coagulant

• UASB effluent – from municipal waste water treatment plant at Bamroli,Surat,India .

• Lab-S V National Institute of Technology ,Surat India .• Charecterisation –standard methods• Coagulation – jar test • Analysis of effluent • Box-Behnken model statistical experimental design with RSM

used to investigate the effect of variables on coagulation

• UASB reactor

• Analytical methods o COD –Standard titration o pH-pH metero Turbidity-Turbidity metero solid content –Standard methods o Phosphate –UV spectrometer o BOD - difference od DO after 5 dayso Total coliform –MPN

Results and discussion• Characterization of WTS and UASB effluent

• Effect of sludge dose ,initial pH and PACl dose

• Process optimization –converting multiple responses in to a single one by combining individual responses in to a composite function followed by its optimization .o COD removal and turbidity removal – ‘maximise’o pH -7 to 9 (disposal standards )o WTS – ‘maximise’o PACl – ‘minimise’

• Inland Surface discharge standards o SS-100 mg/lo COD-250mg/lo BOD- 30mg/lo pH-7 to 9o Total coliform 1000 MPN/100ml

• Optimum conditions for COD and trbidity removal

• Removal when PACL used alone (40 mg/l )o COD- 68%o Turbidity-83%

• Problems o High moisture content of WTS –transport

problem , pre-treatment required o Characterisation and quantification of sludge is

uncertain –difficult to plan reuse option o Design of sludge drying bed in UASB is

difficult , also increase volume

Conclusions

• High removal of COD and Turbidity could be obtained at optimum conditions of WTS dose (15g/l) ,pH (9),PACL dose (4.2 mg Al/l) .Confirmation Experiments gave 79% phosphate removal ,84% suspended solids removal , 78% BOD removal , 99.7% tota coliform removal also .

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