ESEL Paper Review_20110927
 
By Hong Guo

1,Title and Author

Title: Improvement of alum and PACL coagulant by polyacrylamides(PAMs) for the treatment of pulp and paper mill wastewater.

Authors:

A.L.Ahmada,*, S.S. Wong a, T.T. Tengb, A.Zuhairia


a School of Chemical Engineering ,Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulan Pinang, Malaysia.
b School of Industrial Technology , Universiti Sains Malaysia, 11800 Minden, Pulan Pinang, Malaysia

2. Summary of Paper

This paper study to get the coagulation-flocculation efficiencies of alum and PACL when those used alone and in coupled with cationic polyacrylamide(C-PAM) and anionic polyacrylamide (A-PAM) on the treatment of pulp and paper mill wastewater. Here the effects of coagulant dosage, flocculants dosage and pH are studied. The turbidity, TSS(Total Suspend Solid) and chemical oxygen demand(COD) concentrations and Sludge volume index(SVI) are used as evaluating parameters

2.1Coagulation with alum

For the coagulation-flocculation processes using inorganic coagulant, the coagulant dosage and pH play an important role in determining the coagulant efficiency. Here the author  uses the different dosage of the pulp and paper mill wastewater with pre-adjusted pH of 5.0,6.0,7.0,8.0,9.0 , respectively, with the alum dosages of 200,500,800,1000,1500 and 2000 mg/L. then we can find that the optimum range of pH are 5.0~6.5, and the optimum dosage is the 1000mg/L. then the turbidity reduction is 99.8%, TSS removal is 99.4% and COD reduction is 91%
2.2 Coagulation with PACL

When author changes the coagulant as the PACL, we can see that the optimum condition for PACL dosage and pH are 500mg/L and 6.0, respectively, under the condition of the PACL dosage of 50,100,200,500,1000,1500 mg/L and pH adjusted from 5.0 to 10.0. The result reveals that the less PACL dosage than alum and the same pH 6.0 can also give the same coagulation efficiency as alum..

2.3 Add the flocculent dosage

Even without the flocculent, the paper shows us that the alum and PACL also give the high removal efficiency in the area of Turbidity, TSS, and COD. In the case of alum, under the 50 mg/L alum dosage and 1mg/L of flocculent, the turbidity reduction is about 86%. Moreover, 96% is for TSS removal and 86%for COD reduction. It means that lower quantities of alum also can be applied to reduce the Turbidity reduction, TSS removal, COD reduction process under lower criteria. But when the author add the A-PAM,C-PAM, we can find Turbidity reduction, TSS removal are going to be 99% after 200mg/L. the COD reduction will be  higher than 95% in this condition.

2.4 Sludge volume index (SVI)

For the sludge, it can affect the treatment fee and finally can increase the operation cost and fixed cost.  Less sludge production means more cost saving. In this paper, we can see that it would produce about 50mg/L sludge for alum and PACL cases.(PACL is a little less than Alum ). But when we add C-PAM, it reduces the quantity of sludge and improves its dewatering.（30mg/L for Alum and 40mg/L for PACL） On the contrary, A-PAM can increase the quantities of sludge. (60mg/L for Alum and 110mg/L for the PACL) 

3. Contribution:

From the paper we can see that A-PAM and C-PAM can improve the removal performance. In the C-PAM case, it will reduce the sludge volume and reduce the total cost.
The alum and PACL are very important coagulants in the T-P removal process area; the alum can give the excellent reaction performance when the PACL gives us the better sedimentation. 
This paper shows the different performance of alum a PACL when they are used in the pulp and mill water treatment process. Even though there are no T-P removal efficiency are mentioned in this paper, but the Turbidity, TSS and COD also can give us an idea of application of alum and PACL. 
And flocculent are added to the process is very good point to see how can we improve the removal efficiency of Turbidity, TSS and COD in the flocculation-coagulation process.