secondary clarifier (either secondary sedimentation clarifier, or secondary flotation clarifier), the concentrated sludge is separately aerated in the stabilization
tank with a detention time of 2 to 6 hours (based on sludge recycle flow). The
adsorbed organics undergo oxidation in the stabilization tank and are synthesized
into microbial cells. If the detention time is long enough in the stabilization tank,
endogenous respiration will occur, along with a concomitant decrease in excess
biological sludge production. Following stabilization, the reaerated sludge is
mixed with incoming wastewater in the contact tank and the cycle starts anew.
Volatile compounds are driven off to a certain extent by aeration in the contact
and stabilization tanks. Metals will also be partially removed, with accumulation
in the sludge. This process requires smaller total aeration volume than the
conventional activated sludge process. It also can handle greater organic shock
and toxic loadings because of the biological buffering capacity of the stabilization
tank and the fact that at any given time. The majority of the activated sludge is
isolated from the main stream of the plant flow. Generally, the total aeration basin
volume (contact basin plus stabilization basin) is only 50–75 percent of that
required in the conventional activated sludge system. An equalization basin is
generally recommended for equalizing the wastewater influent flow.
Contamination A general term signifying the introduction into water of microorganisms, chemicals, wastes, or sewage, which renders the water unfit for its
intended use.
Conventional biological wastewater treatment system It normally includes
(a) preliminary treatment units (i.e., screen, comminutor, grit chamber, etc., for
removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips,
logs, cans, and other large-sized unwanted materials from raw wastewater),
(b) primary sedimentation clarification for removing mainly total suspended
solids from preliminary effluent, (c) secondary biological treatment units (such
as activated sludge aeration or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon
adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent
discharge standards.
Conventional physicochemical wastewater treatment system It normally
includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber,
etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette
filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary sedimentation clarification for removing mainly total
suspended solids from preliminary effluent, (c) secondary physicochemical treatment units (such as chemical precipitation/coagulation or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic
pollutants from primary effluent, and (d) tertiary treatment plant units (i.e.,
filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary
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M.-H. S. Wang and L. K. Wang
tank with a detention time of 2 to 6 hours (based on sludge recycle flow). The
adsorbed organics undergo oxidation in the stabilization tank and are synthesized
into microbial cells. If the detention time is long enough in the stabilization tank,
endogenous respiration will occur, along with a concomitant decrease in excess
biological sludge production. Following stabilization, the reaerated sludge is
mixed with incoming wastewater in the contact tank and the cycle starts anew.
Volatile compounds are driven off to a certain extent by aeration in the contact
and stabilization tanks. Metals will also be partially removed, with accumulation
in the sludge. This process requires smaller total aeration volume than the
conventional activated sludge process. It also can handle greater organic shock
and toxic loadings because of the biological buffering capacity of the stabilization
tank and the fact that at any given time. The majority of the activated sludge is
isolated from the main stream of the plant flow. Generally, the total aeration basin
volume (contact basin plus stabilization basin) is only 50–75 percent of that
required in the conventional activated sludge system. An equalization basin is
generally recommended for equalizing the wastewater influent flow.
Contamination A general term signifying the introduction into water of microorganisms, chemicals, wastes, or sewage, which renders the water unfit for its
intended use.
Conventional biological wastewater treatment system It normally includes
(a) preliminary treatment units (i.e., screen, comminutor, grit chamber, etc., for
removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips,
logs, cans, and other large-sized unwanted materials from raw wastewater),
(b) primary sedimentation clarification for removing mainly total suspended
solids from preliminary effluent, (c) secondary biological treatment units (such
as activated sludge aeration or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon
adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent
discharge standards.
Conventional physicochemical wastewater treatment system It normally
includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber,
etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette
filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary sedimentation clarification for removing mainly total
suspended solids from preliminary effluent, (c) secondary physicochemical treatment units (such as chemical precipitation/coagulation or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic
pollutants from primary effluent, and (d) tertiary treatment plant units (i.e.,
filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary
440
M.-H. S. Wang and L. K. Wang