The objective of this work was to optimize the ultrasound (US) pretreatment of sludge. Three types of sewage sludge were examined: mixed, secondary and secondary after partial methanisation ("digested" sludge). Thereby, several main process parameters were varied separately or simultaneously: stirrer speed, total solid content of sludge (TS), thermal operating conditions (adiabatic vs. isotherm...

The anionic surfactant linear alkylbenzene sulfonate (LAS) may inhibit soil microorganisms and may occur in agricultural soil through the application of sewage sludge. For five microbial parameters (microbial biomass C and the potentials of iron reduction, ammonium oxidation, dehydrogenase activity, and arylsulfatase activity), we compared the effects of aqueous LAS and LAS-spiked sewage sludge...

Background Part-stream low-frequency ultrasound (LFUS) was one of the common practices for sludge disintegration in full-scale anaerobic digestion (AD) facilities. However, the effectiveness of part-stream LFUS treatment and its effect on AD microbiome have not been fully elucidated. Methods Here we testified the effectiveness of part-stream LFUS pretreatment by treating only a fraction of fe...

The first step of anaerobic digestion, the hydrolysis, is regarded as the rate-limiting step in the degradation of complex organic compounds, such as waste-activated sludge (WAS). The aim of lab-scale experiments was to pre-hydrolyze the sludge by means of low intensive alkaline sludge conditioning before applying hydrodynamic disintegration, as the pre-treatment procedure. Application of both ...

The purpose of this study is to determine how the rheological characterization of centrifuged thickened waste excess activated sludge (EAS). Wastewater treatment plants (WWTP) contain a number of transport operations of suspensions with special flow characteristics. Flow characteristics, in particular viscosity related effects, vary from very water-like to strongly non-Newtonian. This study use...

This paper deals with thermal drying of wastewater sludges, whose management will become crucial in the forthcoming years. Sludges collected after mechanical dewatering in 5 different WWTPs are submitted to the same convective drying treatment in order to try finding some relations between the drying behaviours, the type of effluent and wastewater treatments. Results show dearly sludge drying r...

This work aimed at understanding the combined effect of sludge pH, temperature, and external pressure on the efficiency of sewage sludge ultrasound (US) pretreatment. Based on the evolution of both the degree of sludge disintegration (DDCOD) and pH, application of 40 mgNaOH/gTS during 30 min was selected for chemical pretreatment. Mechanical and thermal effects induced by cavitation contributed...

Environmental pollution has become a world wide concern. One of the main sources of such pollution is sewage wastewater and sludge. Their utilization without proper treatment can pollute the ecosystem (plant, soil, surface and ground water). Sewage wastewater and sludge contains several pollutants such as: pathogens, toxic organic compounds, heavy metals, high level of BOD & COD, seed weed. The...

The high order of a two-input-two-output activated sludge system is reduced using Gawronski and Juang’s frequency limited reduction technique. The manipulated variables are the concentration of nitrate and dissolved oxygen (DO). A reduced fourth order system is obtained within the frequency band of 0.7 rad/s to 1.0 rad/s. The reduced system is compared with a fourth order activated sludge proce...