Page 727 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

682 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

TABLE 22.1
Organic Fractions in Sewage and Secondary Effluent
VS TOC COD
Stage Fraction Size (mm) (mg=L) (f) (mg=L) (f) (mg=L) (f) BOD (mg=L) T (JTU) a
Raw sewage Soluble <10 3 116 0.48 46 0.42 168 40
3
Colloidal 10 –1 23 0.10 12 0.11 43 10
Supracolloid 1–100 43 0.17 22 0.20 87 21
Settleable >100 59 0.25 29 0.27 120 29
Total 241 109 418 200–250 50
Secondary Soluble 62 0.67 16.5 0.69 46 0.74
effluent Colloidal 6 0.7 1.5 0.06 3 0.05
Supracolloid 24 0.26 6 0.25 13 0.21
Settleable 0 0.0 0 0.0 0 0.0
Total 92 24 62 30 b 8
Source: Adapted from Rickert and Hunter, J. Water Pollution Control Federation, 44(1), 135, 1972.
a
T is the turbidity in Jackson candle units (JTU).
b
The value BOD 30 mg=L is a typical value activated sludge after secondary settling and was adopted commonly by states as
an ‘‘effluent discharge standard,’’ pursuant to the 1972 ‘‘Clean Water Act’’ (PL92-500).

process chemicals. The final step, after all other means have
TABLE 22.2 been implemented, is treatment, i.e., pretreatment for dis-
Nitrogen and Phosphorous in Raw Waste, Primary charge into POTWs (public-owned treatment works as
Effluent, and Secondary Effluent defined by PL92-500), or on-site treatment if discharge is

Raw Waste Eff. PS a Eff. FS b into a stream or other water body. Each industry is unique
and generates wastes that are characteristic and may range
Substance Form (mg=L) (mg=L) (mg=L)
from a wide array of organic substances to various metals.
Nitrogen Organic 10–25 7–20 3–6
The main issues in industrial waste discharge into a POTW
as N Dissolved 4–15 4–15 1–3
include (1) whether it contains substances that impair treat-
Suspended 4–15 2–9 1–5
ment due to effect on organisms; (2) whether it contaminates
Ammonia 19–30 10–30 10–30
sludge, such as by heavy metals; and (3) whether it passes
Nitrite 0–0.1 0–0.1 0–0.1
through the plant untreated, perhaps causing a violation of an
Nitrate 0–0.5 0–0.5 0–0.5
effluent discharge permit or a stream standard.
Total 20–50 20–40 15–40
Whether or not a compound is amenable to treatment may
Phosphorous Organic 1–3 0.5–2 0.5–1
be determined by a ‘‘treatability study.’’ As an example, if a
as P Ortho 2–8 1–7 1–8
Condensed 2–8 2–8 1–3 particular waste seems not amenable to treatment, the study is
Total 4–14 3–12 3–11 usually started at the laboratory scale with a diluted sample of
the waste, which is brought into contact with activated sludge.
Source: Adapted from McCarty, P.L., Phosphorous and nitrogen removal The activated-sludge sample is usually obtained from a local
by biological systems, Proceedings of the Wastewater Reclamation municipal wastewater treatment plant (WWTP). The sample
and Reuse Workshop at Lake Tahoe California (226 pages),
is aerated continuously, perhaps for several weeks or even
Sanitary Engineering Research Laboratory, University of
months. During this time period the waste concentrations
California, p. 229, Berkeley, CA, 1970.
a are increased week by week until full strength is reached.
Effluent from primary settling from municipal wastewater treatment.
b At the same time, the microbial culture ‘‘selects’’ toward the
Effluent from secondary settling following biological treatment.
organisms that may metabolize the wastes, probably resulting
in an approximate monoculture. The process is called
‘‘acclimatization.’’
and Agardy, 1998). An axiom in dealing with industrial Regarding references dedicated to industrial wastes, the
wastes has been to reduce the mass flows of different waste texts are few with perhaps a dozen appearing since 1970;
constituents based on a review of practices within a given the most recent are Nemerow and Agardy (1998) and
industry or plant, a traditional approach codified by the 1972 Eckenfelder et al. (2009). In addition, the Purdue Industrial
Clean Water Act (PL92-500). Waste Conference has been the main forum for industrial
Another approach, especially when dealing with industries wastes management starting with its inception in 1944 by
generating hazardous wastes, has been to find substitutes for Professor Don Bloodgood; as of the 1997 conference some