Rotary vacuum drum and vacuum belt filters are extensively used on many process filtration operations, to provide filtration, clarification, dewatering or concentration. Moulded thermoplastic vacuum drum filters are particularly suited to providing continuous filtration of corrosive chemicals, without using expensive or hard to obtain exotic metals such as titanium, stainless steel, monel, Hastelloy or rubber […]
It was stated earlier that industrial filter applications can be divided broadly into two groups, those providing a service to a factory operation, the utility filters, and those acting as a main production unit, the process filters. It was further stated that the utility filters were largely concerned with clarification of a fluid, and so […]
Industrial wastes differ from municipal wastes in three main respects: they are usually much stronger in waste material content (both inorganic and biodegradable); they are often acidic or alkaline in nature rather than neutral; and they frequently contain highly toxic materials. The presence of oils, either as droplets or as an emulsion, is also a problem […]
There are many alternatives to the direct line of treatment processes described in the preceding paragraphs. One such takes the whole sewage, before primary settlement, and treats it at above ambient temperatures with anaerobic bacteria, to produce methane and a benign liquid effluent and separated sludge. This process has many advantages, but is not yet […]
The various stages of sewage processing each produce a sludge in which the wastes from that stage are concentrated, although, of course, in much smaller volumes. These sludges must all be discharged, eventually to the environment, but in as safe a manner as possible. The primary screenings are capable of decomposition and so need very […]
Where the effluent quality after secondary treatment is not good enough to be discharged, then some kind of tertiary treatment will be required. This may be to polish the effluent by removing the last traces of suspended solids. It may be to remove some more of the nutrients nitrogen and phosphorus that would promote unwanted […]
The secondary process treats the residual organic material, both suspended and dissolved in the sewage, by reacting it with aerobic bacteria in an aerated system, so that the bacteria digest the organics and oxygen, growing in the process. This is a timerelated process, with a more complete digestion occurring the longer the reaction is allowed […]
The removal of suspended solids is usually achieved in three processes, an inlet screening, followed by two stages of sedimentation. The influent sewage carries with it a wide range of solid objects that are put into the sewage system or that fall into it, such as dead animals, rags, sticks, human waste, and so on. […]
Sewage treatment thus involves the reduction in concentration of suspended (insoluble) and dissolved impurities to required levels. The overall process is characterized by some important features: ● the quantities involved are very large (they are often measured in ‘ population equivalents’, where waste production is of the order of 150–200 litres per day per capita […]
The treatment of municipal sewage is one of the few processes in commercial life where the managers of the appropriate processing plant have little or no control over the quality of the material coming to the process. The treatment plant must therefore be able to cope with a wide range of flows, containing a wide […]
