Water and wastewater treatment

Wastewater treatment is an extremely important service-related industry that is carefully integrated into our society. Sewage is defined as water that contains one-tenth of 1% (0.1%) solid waste matter produced by human beings. Sewage is frequently referred to as wastewater. Waste-water comes from sinks and toilets of homes, factories, offices, and restaurants. Sewage contains harmful chemicals and disease-producing bacteria. Without processing, this harmful material 

More than 80% of the sewage produced in the United States comes from industrial sources. Primary treatment removes 50% of the heaviest solid material from the sewage. Secondary 

Water and wastewater treatment processes inevitably involve the removal of suspended solids (often referred to as turbidity), usually silt, clay, hydrous oxides and organic matter. Of these, the most difficult suspended solids to remove are the colloidal-sized fraction which, because of their small size, can easily escape both sedimentation and filtration. Examples of these would include spent protein and emulsions from domestic waters, bacterial cells, algae, viruses, amoeba, industrial waste colloids, silts, clays and organic matter from soil wash. Beyond drinking water treatment and industrial wastewater treatment, other application areas include mineral and petroleum processing, and pulp and papermaking, to name just a few. 

The charge on the suspended solids is often sufficiently negative to yield a stable dispersion that settles slowly and is difficult to filter. In this case, the key to effective colloid removal by sedimentation is reduction of the zeta potential to zero or near-zero. Once the charge is reduced or eliminated, electrostatic repulsive forces are minimized. The gentle agitation of the flocculation basin then causes numerous colloid collisions, first with formation of microflocs and then with visible floe particles, which can easily be settled or filtered. Coagulants such as alum, ferric chloride or cationic polymers all function primarily as charge reducers [4,41,42]. 

An alternative to sedimentation for removing suspended solids is flotation. This tends to be used for low-density particles that tend to float anyway during conventional sedimentation processes. Drinking water examples include algae 

An alternative to sedimentation for removing suspended solids is flotation. This tends to be used for low-density particles that tend to float anyway during conventional sedimentation processes. Drinking water examples include algae and floes of humic and fulvic acids that result from the treatment of coloured waters [549]. Wastewater examples include fatty materials, pulp fibres, and oils that can be floated 

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Schroeder, E. D., Water and Wastewater Treatment, McGraw-Hill, New York, 1977. 

D. J. Kjos, R. R. Furgason, and L. L. Edwards, in R. G. Rice and M. E. Browning, eds.. Proceedings of the First Internationa/ Symposium on O nefor Water and Wastewater Treatment, International Ozone Association, Stamford, Coim., 1973, p. 194. 

About 264,000 metric tons of elemental capacity is available in North America, plus another 79,000 t (P equivalent) of purified wet phosphoric acid (14). About 85% of the elemental P is burned to P2 5 hydrated to phosphoric acid. Part of the acid (ca 21%) is used direcdy, but the biggest part is converted to phosphate compounds. Sodium phosphates account for 47% calcium, potassium, and ammonium phosphates account for 17%. Pinal apphcations include home laundry and automatic dishwasher detergents, industrial and institutional cleaners, food and beverages, metal cleaning and treatment, potable water and wastewater treatment, antifree2e, and electronics. The purified wet acid serves the same markets. 

Most carbon adsorption units use granular activated carbon (GAC). The powdered form of activated carbon (PAC) typically is less than 100 microns in diameter and may be used to reduce dioxins in incinerator emissions (2) and in the treatment of drinking water and wastewater treatment (see the section on "Activated Sludge"). 

Chlorine. Chlorine is a weU known disinfectant for water and wastewater treatment, however, it can react with organics to form toxic chlorinated compounds such as the tribalomethanes bromodichloromethane, dibromochloromethane, chloroform [67-66-3] and bromoform [75-25-2]. Chlorine dioxide [10049-04-4] may be used instead since it does not produce the troublesome chlorinated by-products as does chlorine. In addition, by-products formed by chlorine dioxide oxidation tend to be more readHy biodegradable than those of chlorine, however, chlorine dioxide is not suitable for waste streams containing cyanide. 

Elocculants and coagulants are sometimes used as pretreatments before dewatering. The market for flocculants and coagulants for water and wastewater treatment in the United States for 1989 was about 250 million, or 68,000 t, provided by 18 companies. In Europe, 22,000 t of flocculants and coagulants, made by 15 companies, had a market value of 115 million. In Japan, 12 companies made 23,000 t, valued at 184 million (150). 

Pulsed beds of ac tivated carbon are used in water and wastewater treatment systems. The adsorber tank is usually a vertical cylindrical pressure vessel, with fluid distributors at top and bottom, similar to the arrangement of an ion exchanger. The column is filled with granular carbon. Fluid flow is upward, and carbon is intermittently dis-... 

Sutton, P. M. and P. N. Mishra, Biological Fluidized Beds for Water and Wastewater Treatment A State-of-the-Art Review, WPCF Conference, October 1990. 

This brings us to some very basic principles of cost accounting. These concepts were covered in the first volume of this series Handbook of Water and Wastewater Treatment Technologies), but we will repeat a portion of them here because of their particular relevance to plarming air pollution control projects. The... 

Animated training aid and simulation program for water and wastewater treatment plant operators. 

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