Rheological characteristics of municipal thickened excess activated sludge (TEAS): impacts of pH, temperature, solid concentration and polymer dose

Abstract

Rheological characterization of sludge is known to be an essential tool to optimize flow, mixing and other process parameters in wastewater treatment plants. This study deals with the characterization of thickened excess activated sludge in comparison to raw primary sludge and excess activated sludge. The effects of key parameters (total solid concentration, temperature, and pH) on the rheology and flow behaviour of thickened excess activated sludge were studied. The rheological investigations were carried out for total solid concentration range of 0.9%w/w-3.7%w/w, temperature range of 23°C-55°C, and pH range of 3.6-10.0. Different rheological model equations were fitted to the experimental data. The model equations with better fitting were used to calculate the yield stress, apparent, zerorate, infinite-rate viscosities, flow consistency index, and flow index. The decrease in concentration from 3.7%w/w to 3.1%w/w resulted in drastic reduction of yield stress from 27.6Pa to 11.0Pa, and further reduction of yield stress to 1.3Pa was observed as solid concentration was reduced to 1.3%w/w. The viscosity at higher shear rate (>600s-1) decreased from 0.05Pa.s down to 0.008Pa.s when the total solid concentration was reduced from 3.7% to 0.9%. Yield stress decreased from 20.1Pa down to 8.3Pa for Bingham plastic model when temperature was raised from 25˚C to 55˚C. Activation energy and viscosity also showed decreasing trend with increasing temperature. Yield stress of thickened excess activated sludge increased from a value of 6.0Pa to 8.3Pa when pH was increased from 3.6 to 10.0. The effect of polymer dose on the rheological behaviour of thickening of excess activated sludge was also investigated, and the optimum polymer dosage for enhanced thickener performance was determined to be 1.3kg/ton DS.

Effects of Temperature, Polymer Dose, and Solid Concentration on the Rheological Characteristics and Dewaterability of Digested Sludge of Wastewater Treatment Plant (WWTP)

“…These changes directly influence the rheological properties of digested sludge during dewatering (Sanin 2002). Viscosity generally lowers with higher temperature and shear rate, and a similar trend was reported by many researchers (Farno et al 2013;Eshtiaghi et al 2013;Hasar et al 2004;Yeneneh 2014;Hong et al 2015Hong et al , 2016.…”

“…Rheological and fluid dynamic characteristics of sludge are also essential in the design and operation of processes in wastewater treatment plants due to their influence on heat and mass transfer and mixing (Baroutian et al 2013;Bandrés et al 2009). The rheological characteristics of digested sludge depend on many factors such as source, solid concentration, temperature, and sludge treatment method (Ratkovich et al 2013;Abu-Jdayil et al 2010;Hong et al 2015Hong et al , 2016. Total solid concentration is one of the major factors that affect the rheology and flow behavio of digested sludge.…”

Analysis of the Bioaugmentation Potential of Pseudomonas putida OR45a and Pseudomonas putida KB3 in the Sequencing Batch Reactors Fed with the Phenolic Landfill Leachate

“…On the other hand, the gradual decrease in the removal efficiency of the COD from 95% to 45% in noninoculated bioreactor exposed to the leachate resulted in the formation of very poor-quality effluent with a quality index of 250 and strongly alkaline pH. The pH of wastewater is considered to be among the most critical factors for the stable operation of sewage plants because it affects the strength and surface charge of the sludge flocs [45]. It can be concluded that the bioaugmentation of the AS with Pseudomonas strains made it possible to maintain the system stability because these bacteria positively affected the microbial biodegradation of the contaminants in the sewage and thus helped to maintain stable pH conditions.…”

Impact of the Biological Cotreatment of the Kalina Pond Leachate on Laboratory Sequencing Batch Reactor Operation and Activated Sludge Quality

“…The appropriate pH is a crucial factor for the stable operation of a sewage plant because it affects the strength and surface charge of the AS flocs [63]. Extreme pH conditions can lead to an inhibition of the growth of the AS microorganisms [64].…”