Wastewater characteristics solids

Environmental factors include (a) the impact of control technology on ambient air quality (b) the contribution of the pollution control system to the volume and characteristics of wastewater and solid waste generation and (c) maximum allowable emissions requirements. 

Municipal wastewater characteristics are dependent on a number of factors that include solids, wastewater volume, and chemical content. The factors can change rapidly in response to daily and seasonal variations, precipitation, industrial discharges, and public habits. Combination of these factors can result in significant hourly fluctuations in wastewater characteristics. 

Nitrobenzene in aqueous samples may be analyzed by GC and GC/MS techniques. Wastewaters and solid and hazardous wastes may be analyzed by EPA Methods 609 (GC) or 625 and 8250 or 8270, respectively, using GC/MS (U.S. EPA 1992, 1997). The characteristic ions to identify nitrobenzene by mass spectroscopy (electron-impact ionization) are 77, 123, and 65. The GC techniques involve the use of FID and NPD (in the nitrogen mode) as detectors. The former is less sensitive than the latter. 

Analysis cf Physicochemical Parameters The wastewater characteristics such as pH, COD, BOD, total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), total alkalinity and total acidity as acetic acid were determined as per standard methods (APHA). The treated wastewater samples were centrifuged (Remi Instruments, Mumbai) to obtain a clear supernatant and precipitate. The COD of the effluent, before and after treatment, was determined by the standard dichromate closed reflux method as per the standard. The COD value was assayed with a COD analyser (Aqualytic, Germany). 

Biological wastewater treatment processes also affect solids characteristics and hence solids separation. Activated sludge solids have been found to have a distinct bimodal distribution with one mode in the supracolloidal to settleable range and another near the border between the colloidal and supracolloidal fractions. The concentrations and size limits in each range are affected by conditions in the... 

TETRA HDS [High density solids] A process for aiding the removal of heavy metals from wastewaters. It is a physical process which controls the characteristics of heavy metal hydroxide precipitates so that they settle quicker. The precipitates have a hydrophobic surface, so they are easy to de-water. Developed and licensed by Tetra Technologies, Houston, TX. Widely used by the iron and steel industry in the United States. Not to be confused with hydrodesulfurization, often abbreviated to HDS. 

Microbial transformations and generally not chemical transformations characterize the sewer environment in terms of quality transformations of the wastewater. On the other hand, the physicochemical characteristics, e.g., diffusion in the biofilm and exchange of substances across the water-air interface, play an important role and must be integrated with the microbial transformations. The hydraulics and the sewer solids transport processes have a pronounced impact on the sewer performance. These physical processes, however, are typically dealt with in hydraulics and are, therefore, only included in the text when directly and closely related to the chemical and biological processes. 

The occurrence of sewer sediments is primarily determined by the physical characteristics of wastewater solids and the hydraulic conditions. Basically, sewers should be designed and operated in a way that does not result in permanent deposits. This ideal performance of a sewer is not generally observed, and sediments may be more or less temporarily accumulated in sewers. In combined sewer networks, sediments may settle under dry-weather conditions when the wastewater velocity and shear stress at the bottom are low and be... 

Wet-weather processes have, in general, been excluded in the text, because they are based on a different concept and perform differently. Microbial and physicochemical processes are contrary to the physical processes dominating in sewers during dry-weather transport of the wastewater. When dealing with combined sewer networks in terms of pollutant loads during overflow events, dry-weather solids deposition and erosion and solids transport during high-flow events are, in addition to the rainfall/runoff hydraulic and sewer solids characteristics, the central physical in-sewer processes. Quite different process approaches are, therefore, required to describe dry-weather and wet-weather sewer performance. 

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