Sludge Density Prediction in a Wastewater Chemical Coagulation Process

Margarita Teutli-León, María Elena Pérez-López

Engineering Department, Autonomous University of Puebla (BUAP), Puebla, Mexico.
Interdiciplinary Research Center for the Local Integral Research, National Polytechnical Institute at Durango (IPN-CIIDIR-DGO), Durango, Mexico.

DOI: 10.4236/jwarp.2013.57A001                

Abstract

This paper reports an approach to estimate the sludge density in a physicochemical treatment of municipal wastewater, experiments considered 4 coagulants (aluminum sulfate SAl, iron sulfate SFe, aluminum polychloride PAX, iron polychloride PIX), and 2 flocculant products (cationic CP and anionic AP polymers). Experimental approach is based on running a set of jar tests at different coagulant concentrations. After the stirring and resting times took place, pH and conductivity were registered finding that SAl and SFe either with or without polymers are the coagulants producing the higher pH drop. Conductivity measures also establish two kind of data since higher conductivity (about 2000 ) was observed for SAl, and PIX, PIX + CP, PIX + AP; otherwise a conductivity about 1300 was observed for SAl + PC, SFe and PAX alone and with CP or AP. Settleable solids (SST) determined with an Imhoff cone were similar for sulfates and polychlorides, but dry sludge (DS) clearly set up two groups the one with higher sludge content corresponds to sulfates group. The quotient of DS divided by the SST provided an estimation of the apparent sludge density, in this way it was observed that higher densities were obtained for sludge from sulfates at lower coagulant concentrations; also sludge from SFe was heavier than the one from SAl. Otherwise, polychlorides produced a lighter sludge in respect to the one obtained with sulfates, and between them the PIX coagulant provided a heavier sludge than the PAX coagulant.

Keywords

Coagulant; Flocculant; Wastewater Treatment; Sludge Density

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	P. A. Vesilind, “Wastewater Treatment Plant Design,” Water Environment Federation US, 2003.
[2]	W. P. Freese, “Influence of Wastewater Treatment on Sludge Production and Processing,” Water and Environment Journal, 2013, pp. 1-10 (in Press).
[3]	I. M. C. Lo, K. C. K. Lai and G. H. Chen, “Salinity Effect on Mechanical Dewatering of Sludge with and without Chemical Conditioning,” Environmental Science & Technology, Vol. 35, No. 23, 2001, pp. 4691-4696. doi:10.1021/es010834x
[4]	D. Kalderis, M. Aivalioti and E. Gidarakos, “Options for Sustainable Sewage Sludge Management in Small Wastewater Treatment Plant on Islands: The Case of Crete,” Desalination, Vol. 260, No. 1-3, 2010, pp. 211-217. doi:10.1016/j.desal.2010.04.030