Wastewater minimization/reduction

The processes used in manufacturing steel products use a significant amount of water, and wastewater minimization is necessary both in terms of water use and pollutant discharge loadings. These technologies achieve these reductions by retarding pollutant buildup and improving water... 

Following the chlorine chemical contact for disinfection, described in the previous section, residual chlorine must be removed using a dechlorination agent such as sulfur dioxide (Fig. 8). This quenching of the chlorine (or chloramine) by a strong reductant provides a potential for the chemical reduction of transformation products in the wastewater. Minimal research has addressed these reductive reactions for transformation products of synthetic organic chemicals. 

All point source and nonpoint source wastewaters at an industrial site must be properly managed for source separation, waste minimization, volume reduction, collection, pretreatment, and/or complete end-of-pipe treatment [39,47]. When industrial waste is not disposed of properly, hazardous substances may contaminate a nearby surface water (river, lake, sea, or ocean) and/or groundwater. Any hazardous substance release, either intentionally or unintentionally, increases the risk of water supply contamination and human disease. Major waterborne contaminants and their health effects are listed below. 

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. 

Continuous chromium reduction treatment requires a tank for acidification and reduction with separate tanks for precipitation and sedimentation. The retention time in the reduction tank is dependent on the pH employed but should be at least four times the theoretical time for complete reduction. In cases where the chromium content of the wastewater varies markedly, equalization should be provided prior to the reduction tank to minimize fluctuations in the chemical feed system. Successful operation of a continuous chrome reduction process requires instrumentation and automatic control. Redox and pH control should also be provided. 

Reduction of wastewater flow with simultaneous minimization of COD, AOX, and salt load... 

Even if care is taken to minimize waste, there will still be waste to treat. Currently used wet finishing processes produce waste containing organic as well as inorganic compounds. The efflnents are rich in chemicals of which some are persistent or resistant to water treatment methods. Table 2.1 lists typical examples of finishing waste that resists biodegradation. Removal of these substances from wastewater is expensive and difficult to achieve. Because of this, the effiuent segregation and source reduction methods are preferred as economically attractive alternatives. 

The properties of the two process streams (permeate and craicentrate) are of particular importance since these characteristics define waste disposal options. The permeate stream should exhibit significant reductions in contamination so as to allow economical discharge to local wastewater treatment facilities without extensive pretreatment requirements. The concentrate stream should be volumetrically small, relative to the original feed, in order to minimize the volume of waste requiring further treatment prior to disposal. Furthermore, the filtration process should enable the use of additional disposal options for the concentrate (as compared to the raw feed). 

When applying a membrane solution to a wastewater problem it is crucial to evaluate the balance between permeate quality and volume reduaion. Maximizing volume reduction is important since it impacts economics by minimizing the volume of wastewater requiring treatment. However, the quality of the discharged water is critical and must be maintained during the filtration process. Treatability testing is necessary to determine the optimal balance between permeate quality and volume reduaion. 

The filtration system is a volume reduction technology, and as such minimizes the volume of wastewater that would require treatment. The technology was demonstrated as a method to reduce the volume of wood preserving waste contaminated groundwater. Therefore, treatment of the concentrate is not part of the demonstrated... 

Results showed a 95-98 % reduction in COD and color for hydrocarbon and dye contaminated wastewater. Sludge generation was relatively low, compared to traditional chemical treatments. Energy consumption was minimized, producing treated water of desired quality for reuse at relatively low cost - and therefore attractive to industry. 

Hall, Freddie E., Jr., OC-ALC Hazardous Waste Minimization Strategy Reduction of Industrial Biological Sludge from Industrial Wastewater Treatment... 

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