INDUSTRIAL WASTE MANAGEMENT 531
measures include: (1) materials balance accounting; (2)
improved process control; (3) more effective cleanup proce-
dures; (4) regular preventive maintenance; and (5) by-product
recovery. Poor maintenance and cleanup procedures in many
industrial plants are a major source of wasteload generation.
Product spills should be avoided, and when they occur,
the waste should be handled in a manner that will minimize
the contribution of wasteload to the plant. Proper housekeep-
ing procedures should be developed and implemented.Waste SegregationIt is important to segregate all wastes in accordance with
the physical and chemical properties of the contaminants,
potential to react, and their treatability. Important properties
are suspended solids, acidity, basicity, organic matter and
biodegradability, volatility, and toxic organics and inorgan-
ics. Efforts should be made to minimize dilution of waste
streams prior to treatment and/or recovery of residuals.
Diluted streams should be handled separately.Water Conservation and RecycleWater conservation and recycle consist of minimizing the
raw water supply and maximizing the amount or wastewater
reuse within the plant. The net effect of water conservation
and recycle is the reduction of wastewater volume and to
concentration of wasteloads.
Each process should be investigated to minimize water
supply requirements and the potential for substituting recy-
cled or reclaimed wastewater for fresh water. Water qual-
ity requirements for most industrial processes will govern
the feasibility or extent of water reuse. However, in every
industry using water for washing, rinsing, or cooling, some
form of countercurrent flow or recycling can probably be
implemented for maximum reuse. Some specific recom-
mendations for water conservation and recycle include:
(1) dry (nonwater) cleaning method, (2) water meters at
each department to make operators conscious of usage,
(3) automatic valves that close when water is no longer
required, (4) regular preventive maintenance programs that
include leak surveys, and (5) cleanup with high-pressure,
low-volume rinse sprays.^16Process ModificationIn-plant process modifications, though more costly to imple-
ment than simple operational changes, may be very effective
in controlling wasteload generation. Process modifications
may consist of individual unit process changes, or changes to
a complete process line. The cost-effectiveness of such modi-
fications will depend on the relative reduction in wasteloads.
In older industrial plants, required process modifications may
be accomplished during the installation of newer and more
efficient equipment. In the design of new plants, each pro-
cess should be evaluated with respect to use of more efficient
equipment for maximum water conservation and minimum
wasteload generation.Liquid Treatment SystemsThe removal of various contaminants from the liquid depends
on the nature of the impurities and their concentrations.
Coarse and settleable inorganic and organic solids are gener-
ally removed in sedimentation facilities. Oil and grease is
removed by skimmers. The removal of dissolved organics is
readily achieved in biological or chemical or physicochemi-
cal treatment processes. For example, chemical oxidation-
reduction reactions and precipitation are used for removal
of heavy metals. Carbon adsorption can be used to remove
refractory organics. Ion exchange and membrane processes
are suitable for demineralization and byproduct recovery.
Major physical, chemical, and biological treatment pro-
cesses used for liquid treatment are summarized in Table 3.
For extensive presentations on these processes the readers
should refer to several excellent publications that provide
detailed discussions on the theory and design of wastewater
treatment processes. 2, 25 – 31Sludge and Brine Processing and DisposalSafe handling and disposal of residues and brines pro-
duced in various treatment units are of equal importance.
Solids portions include screenings, grit, scum, organic and
inorganic sludges. Brines (high mineral concentrates) are
produced from ion exchange, reverse osmosis, and electro-
dialysis units. In general, the sludge processing and disposal
methods include thickening, stabilization, and dewatering or
evaporation of liquid. Several of the unit operations and pro-
cesses used for sludge and brine handling and disposal are
illustrated in Figure 1.MAJOR INDUSTRIAL WASTES AND TREATMENTIt should be recognized that to truly understand the waste
problem of any industry, a lifetime serious effort on the part
of a qualified waste engineer may be required. Production
methods of each industry are normally different. As a result,
the treatment process train needed for the waste streams
should be individually designed. The purpose of this section
is to review the origin and characteristics of wastewater and
methods of wastewater treatment for six major industries. In
the following discussion, the reader will find a brief sum-
mary of the major liquid wastes, their origin, characteristics
and current methods of treatment for food, paper and allied
products, chemical, petroleum, metals, and power generation
industries. For a detailed study on these topics the readers
should refer to several references on the subject included in
the list of references. 32 – 35Food IndustryThere are approximately 50,000 food processing plants in
the total food processing industry in the United States.
Food processing is a low-profit margin, highly com-
petitive industry. Water is required for washing, blanching,C009_004_r03.indd 531C009_004_r03.indd 531 11/18/2005 10:31:54 AM11/18/2005 10:31:54 AM