WASTEWATER SLUDGE AS AN ALTERNATIVE ENERGY RESOURCE: A REVIEW

<p align="justify">In recent years, concerns regarding to wastewater sludge disposal have increased globally. Production of sludge has increased recently due to the growth of population. Wastewater sludge classified as a hazardous substance, it is not easy to dispose because of certain treatment is required. Typically, sludge is treated at secured landfill which its limited in availability and expensive. On the other hand, wastewater sludge originated from biological treatment contains organic substance that can be converted into alternative energy resources. A technology is needed that is able to reduce the volume of sludge and convert sludge into energy source. We present an overview of various technologies that can be used for conversion of sludge into energy resources. Those technologies are anaerobic digestion, pelletization, combustion, pyrolysis and gasification. Progress and challenges of each technology is presented in detail. A summary of sludge characteristic originated from different source will be discussed as well. Emissions and residues that determines the environmental impact is also considered. Referring to some previous research, it known that wastewater sludge, as unwanted product, has the potential to become future energy resource. This potential can only be used properly if the method of conversion are effective and efficient.</p>

A Model for Characterizing the Process of Activated Sludge Compression Settling

Based on batch settling tests, a model describing the compression settling stage was developed and validated by experimental data. A equation determining the critical point when the compression settling stage commences, and a new velocity function for compression settling process were deduced from the model. It was shown that compression settling velocity, time and sludge concentration of the critical point occurrence depend on the initial sludge concentrations, the initial sludge blanket height and the sludge characteristic. Dividing the entire settling process of activated sludge into the zone settling and compression settling stages, and describing them by respective velocity models was more reasonable for characterizing the entire settling behaviour of activated sludge. The method was applied to predict the sludge blanket height during batch settling tests, and the results showed that the settling processes could be simulated well.

Suivi du fonctionnement d'une station d'epuration associant physico-chimie et biofiltration = Metabief (France)

The sewage treatment plant of Metabief (East of France) has been monitored during three weeks in winter 1988. The treatment associates a physico-chemical treatment with a biological process of biofiltration. The first step eliminates about 60 % of the organic matter (COD and BOD). The biofliters improve the treatment removing 60 % of COD influent and 65 % of TSS. The process is efficient (N excepted) under conditions of the experiment but nitrification is limited by cold temperatures (&lt; 10°C). Important results related to biological sludge product are presented (sludge characteristic, microscopic data, sludge production). Power consumption of biofliters represents 70 % of the total plant needs. Adequate control of washing cycles and close survey of numerous movable devices are of the utmost importance to guarantee the proper operating of biofliters.