Anaerobic waste treatment processes

In addition, the solid residue from anaerobic waste treatment processes is a valuable fertilizer, which is stabilized and almost odorless. This fertilizer is especially a benefit in developing countries, due to its potential to boost crop yields. 

Toxicity, Synergism, and Antagonism in Anaerobic Waste Treatment Processes... 

During the last 10 years, much fundamental information has been discovered concerning anaerobic waste treatment. With judicious use of this information, anaerobic waste treatment systems can be designed and operated in a less empirical and more efficient manner than previously. Included in these fundamental findings are basic data on toxicity. This paper presents a review of the available information on toxicity in anaerobic waste treatment. The data have been analyzed and are presented from the viewpoint of the waste treatment engineer. This mode of presentation was chosen to facilitate the utilization of the data presented and thus expand the applicability of the anaerobic waste treatment process. 

Therefore, a prime objective in the operation of anaerobic waste treatment processes is maintenance of a proper pH range. The signal that trouble is imminent is a sudden rise in the volatile acids. One group of investigators has indicated that the proper action to take when the volatile acids rise suddenly is to add alkaline substances to maintain the buffer capacity 12, 13, 14), A second group led by Buswell 15) and Schlenz 16) contends that this is detrimental because the volatile acids themselves are toxic to methane bacteria but not to acid formers at concentrations of about 2000 mg/liter. The use of alkaline materials thus only stimulates acid production leading to even greater toxicity. This latter... 

Figure 1. Schematic of two anaerobic waste treatment processes...

Table 19.2 Advantages and disadvantages of anaerobic waste treatment processes compared to aerobic treatment...

Biodegradability - Metabolix PHA offer hydrolytic stability under normal service conditions but when exposed to microbial organisms naturally present they break down enzymatically in soil, composting, waste treatment processes, river water and marine environments. They also rapidly decompose to carbon dioxide and water and will degrade in anaerobic environments, unlike some other biodegradable polymers. 

As a result, specified periods of time, specific disposal pathways, and standard test methodologies were incorporated into definitions. Standardisation organisations such as CEN, ISO, and ASTM were consequently encouraged to rapidly develop standard biodegradation tests so these could be determined. Society further demanded undebatable criteria for the evaluation of the suitability of polymeric materials for disposal in specific waste streams such as composting or anaerobic digestion. Biodegradability is usually just one of the essential criteria, besides ecotoxicity, effects on waste treatment processes, etc. 

This combination of anaerobic and aerobic environment adds some complexity to the process but enables larger loads to be purified such as shown in Figure 2-23. One of the primary effluent gasses is trimethylamine. This tertiary amine has the very characteristic odor of rotten fish. Combustion methods can be used to treat this waste but these will produce NOj, effluents unless very special measures are employed in waste treatment. An alternative wet chemical processes was developed (Bohrer, 1999). The liquid solution waste can also be oxidized to produce a non-odoriferous solid using hydrogen peroxide. This alternative waste treatment process keeps the nitrogen fixed, reducing the atmospheric... 

UOP FCC unit, 11 700-702 UOP/HYDRO MTO process, 18 568 UOP Olex olefin separation process, 17 724 Up-and-Down Method, 25 217 U/Pb decay schemes, 25 393-394 Updraft sintering, 26 565 Upflow anaerobic sludge blanket (UASB) in biological waste treatment, 25 902 Upgraded slag (UGS), 25 12, 33 Upland Cotton, U.S., 8 13 U-Polymer, 20 189 Upper critical solution temperature (UCST), 20 320, 322 Upper explosive limit (UEL), 22 840 Upper flammability limit, 23 115 Upper flammable limit (UFL), 22 840 Upper Freeport (MVB) coal... 

O. Bernard, D. Dochain, A. Genovesi, A. Punal, D. Perez-Alvarino, J.P. Steyer, and J. Lema. Software sensor design for an anaerobic wastewater treatment plant. In IFAC-Intemational Workshop on Decision and Control in Waste Bio-Processing, Narbonne, Prance, 1998. 

A bioreactor is a vessel in which biochemical transformation of reactants occurs by the action of biological agents such as organisms or in vitro cellular components such as enzymes. This type of reactor is widely used in food and fermentation industries, in waste treatment, and in many biomedical facilities. There are two broad categories of bioreactors fermentation and enzyme (cell-free) reactors. Depending on the process requirements (aerobic, anaerobic, solid state, immobilized), numerous subdivisions of this classification are possible (Moo-Young, 1986). 

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