Importance of Improved Wastewater Characterization

Importance of Improved Wastewater Characterization

Improved Analytical Techniques

Great strides in analytical techniques have been made with the development of new and more sophisticated instrumentation. While most constituent concentrations are reported in milligrams per liter (mg/L), measurements in micrograms per liter (µg/L) and nanograms per liter (ng/L) are now common. As detection methods become more sensitive and a broader range of compounds are monitored in water supplies, more contaminants that affect humans and the environment will be found. Many trace compounds and microorganisms, such as Giardia lamblia and Cryptosporidium parvum, have been identified that potentially may cause adverse health effects. Increased analytical sophistication also allows the scientist and engineer to gain greater knowledge of the behavior of wastewater constituents and how they affect process performance and effluent quality.

Importance of Improved Wastewater Characterization

Because of changing wastewater characteristics and the imposition of stricter limits on wastewater discharges and biosolids that are used beneficially, greater emphasis is being placed on wastewater characterization. Because process modeling is widely used in the design and optimization of biological treatment processes (e.g., activated sludge), thorough characterization of wastewater, particularly wastewaters containing industrial waste, is increasingly important. Process modeling for activated sludge as it is currently conceived requires experimental assessment of kinetic and stoichiometric constants. Fractionization of organic nitrogen, chemical oxygen demand (COD), and total organic carbon into soluble and particulate constituents is now used to optimize the performance of both existing and proposed new biological treatment plants designed to achieve nutrient removal. Techniques from the microbiological sciences, such as RNA and DNA typing, are being used to identify the active mass in biological treatment processes.

Waste water Disinfection.

Changes in regulations and the development of new technologies have affected the design of disinfection systems. Gene probes are now being used to identify where specific groups of organisms are found in treated secondary effluent (i.e., in suspension or particle-associated). Historically, chlorine has been the disinfectant of choice for wastewater. With the increasing number of permits requiring low or non detectable amounts of chlorine residual in treated effluents, dechlorination facilities have had to be added, or chlorination systems have been replaced by alternative disinfection systems such as ultraviolet (UV) radiation (see Fig. 1-6). Con- cerns about chemical safety have also affected design considerations of chlorination and dechlorination systems. Improvements that have been made in UV lamp and bal- last design within the past 10 years have improved significantly the performance and reliability of UV disinfection systems. Effective guidelines have also been developed for the application and design of UV systems (NWRI, 2000). Capital and operating costs have also been lowered. It is anticipated that the application of UV for treated drinking water and for storm water will continue to increase in the future. Because UV produces essentially no troublesome by-products and is also effective in the reduction of NDMA and other related compounds, its use for disinfection is further enhanced as compared to chlorine compounds.