Sludge anaerobic

Keywords Activated sludge, Anaerobic treatment, Hormones, Nonylphenol, Pharmaceuticals... 

Parameter Primary influent Primary effluent Primary sludge Secondary effluent Waste activated sludge Anaerobic digester feed Centrifuge supernatant Centrifuge sludge... 

Waste treatment Activated sludge Anaerobic oxidation of NHj Bioranediation... 

Block copolymer of PVA and 1,1 dicarboxylated malonate copolymer. M = 9000-24,000 VA block content 8-72% Biochemical oxygen demand, molecular weight, CO2 evolution, organic carbon analysis River water culture isolates (aerobic) River sediment or anaerobic activated sludge (anaerobic) [136]... 

Table 2.1 Composition of landfill gas and biogas from farm plants and sewage sludge anaerobic digesters. 

Another suspended growth method is the upward-flow anaerobic sludge blanket illustrated in Fig. 11.6a. Here the sludge is contacted by upward flow of the feed at a velocity such that the sludge is not carried out of the top of the digester. 

A third method of contact known as an anaerobic filter also uses upward flow but keeps the sludge in the digester by a physical barrier such as a grid. 

In all types of biological processes, excess sludge is produced which must be disposed of. The treatment and disposal of sludge are major problems which can be costly to deal with. Anaerobic processes have the advantage here, since they produce considerably less sludge than aerobic processes (on the order of 5 percent of aerobic processes for the same throughput). 

Water Groundwater can be treated in anaerobic bioreactors that encourage the growth of sulfate reducing bacteria, where the metals are reduced to insoluble sulfides, and concentrated in the sludge. For example, such a system is in use to decontaminate a zinc smelter site in the Netherlands (95). 

Ana.eroblc Digestion. Methane can be produced from water slurries of biomass by anaerobic digestion in the presence of mixed populations of anaerobes. This process has been used for many years to stabilize municipal sewage sludges for purposes of disposal. Presuming the biomass is all cellulose, the chemistry can be represented in simplified form as follows ... 

The microorganisms grow in response to the food source suppHed in the wastewater and produce more biological sludge than is needed to maintain the process. This excess sludge must be wasted from the process and is usually treated by dewatering and aerobic or anaerobic digestion. 

Biolog ic lRemoval. Certain organisms normally present in activated sludge have the abiUty to store phosphoms. The process configuration for bio-P removal involves an anaerobic step in which phosphoms is released and acetate taken up by the bio-P organisms. This is followed by an aerobic step in which phosphoms is rapidly taken up by the bio-P. Under proper operating conditions, soluble effluent phosphoms levels of 0.1 mg/L are achievable from municipal wastewater. 

Anaerobic Contact. This process can be considered as an anaerobic activated sludge because sludge is recycled from a clarifier or separator to the reactor. Siace the material leaving the reactor is a gas—Hquid—soHd mixture, a vacuum degasifier is required to separate the gas and avoid floating sludge ia the clarifier. 

Sludge Stabilization. Organic sludges need to be stabilized before ultimate disposal except in the case of incineration. This is usually achieved by either aerobic or anaerobic digestion. In aerobic digestion, the degradable volatile soHds are Hquefted and oxidized to CO2 and H2O. In anaerobic digestion the soHds are Hquefted and fermented to CH and CO2. 

Fig. 3. Process components for the activated-sludge process, with aerobic digestion at plants <473.1 m /h and two-stage anaerobic digestion at plants...

Sludge is destroyed by microorganisms and the kinetics of their life processes is temperature dependent. Short anaerobic digestion detention times are obtained at 35°C. Even shorter detention times are possible at 52—54°C, but detention in this range is costly. An increase in detention time occurs at 35—43°C and then a progressive decrease takes place until 52—54°C. This variation is caused by a change in character of the dominant process organisms. 

---