Tertiary treatment systems

Soil may be viewed as a natnral filter for wastes and one that rates very high in sustainability. Most organic matter is readily degraded in soil, and, in principle, soil constitutes an excellent primary, secondary, and tertiary treatment system for water. Soil has physical, chemical, and biological characteristics that can enable wastewater detoxification, biodegradation, chemical decomposition. 

Process water streams from vinyl chloride manufacture are typically steam-stripped to remove volatile organics, neutralized, and then treated in an activated sludge system to remove any nonvolatile organics. If fluidized-bed oxychlorination is used, the process wastewater may also contain suspended catalyst fines and dissolved metals. The former can easily be removed by sedimentation, and the latter by precipitation. Depending on the specific catalyst formulation and outfall limitations, tertiary treatment may be needed to reduce dissolved metals to acceptable levels. 

Fluidized-bed powdered activated carbon systems represent another important process. The use of activated carbon for the tertiary treatment of secondary sewage effluents has been used extensively. Powdered carbon is as effective as granular activated carbon for removing the organic impurities from the wastewater. 

The design of a waste treatment system requires data that was not available to me. A secondary system to reduce the biological oxygen demand and a tertiary system to at least remove most of the phosphates are required. Whether styrene is biodegradable was not known. If it is not, then the tertiary system will have to be designed to remove it also. 

Chemical treatment is what the name implies-the addition of a foreign substance to effect the removal of unwanted substances. This includes such operations as neutralization, coagulation, ion exchange, and electrodialysis. These, along with the advanced physical systems, have been referred to at times as tertiary treatment or advanced treatment processes. 

The competitive physical/chemical system that is being installed at Rosemount, Minn., consists of primary treatment followed by coagulation, sand filtration, activated carbon adsorption, another filtration step, ion exchange, and oxidation. This can produce a highly purified water at less cost than a system involving primary, secondary, and tertiary treatment.30... 

Tertiary carbon systems have, in general, performed more successfully than IPCT systems in municipal waste treatment applications. This is due in part to the increased adsorptive loading required of IPCT systems over tertiary units in which the carbon beds are merely polishing filters. Both tertiary and IPCT applications have been beset by design and/or operational difficulties, the majority of which have been mechanical in nature rather than failures in process performance. However, these problems have tended to be more severe in IPCT cases in terms of system impact as well as in fact. In IPCT plants, the carbon system is more central to overall treatment than in tertiary units, hence system failures in the former applications make achievement of discharge permits virtually impossible. 

Wastewater treatment systems can be classified, in addition to pretreatment, as preliminary, primary, secondary, and tertiary (advanced) treatments. Pretreatment of industrial wastewater is required to prevent adverse effects on the municipal wastewater treatment plants. Preliminary treatment is considered as any physical or chemical process that precedes primary treatment. The preliminary treatment processes may consist of influent screening and grit removal. Its function is mainly to protect subsequent treatment units and to minimize operational problems. Primary treatment is defined as the physical or chemical treatment for the removal of settleable and floatable materials. The screened, degritted raw wastewater from preliminary treatment flows to the primary clarification tanks, which are part of the primary treatment facilities. Secondary wastewater treatment is the process that uses biological and chemical treatment to accomplish substantial removal of dissolved organics and colloidal materials. The secondary treatment facilities may be comprised of biological reactor and secondary clarification basins. Tertiary (advanced) wastewater treatment is used to achieve pollutant reductions by methods other than those used in primary and secondary treatments. The objective of tertiary wastewater treatment is to improve the overall removal of suspended solids, organic matter, dissolved solids, toxic substances, and nutrients. 

Ozonation system consists of the following sections a. feed-gas treatment b. ozone generation c. ozone-water contact mechanism and d. destruction unit (Lin S.H., 1993). The use of ozonation in preliminary treatment is not economic effective even it can decrease the soluble organic. Therefore, it is better to implement Ozonation in tertiary treatment for effectively colour removal of the residual dyes. 

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