Page 58 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Water Treatment 13

process=technology. Other situations, such as at mine drain- into account noise problems associated with pumps; design-
age site, may include heavy metals in which case precipitation ing rooms with windows; placing signs to accommodate
is a likely unit process. In some cases, hyper-filtration is visitors and public tours, a reception area, etc.
added, mainly for redundancy.
1.5.1.2 Managing a Team
In addition to the management of staff, the engineer assumes
1.4.5 HAZARDOUS WASTES:IN SITU TREATMENT the de facto leadership and management of an informal team
that may include the owner and perhaps a representative from
In some cases, in situ treatment is applied. A main technical
the political body, operators, regulatory authorities, equip-
problem is to get the reactants in contact with one another,
ment manufacturer’s representatives, the suppliers of mater-
i.e., how to ‘‘transport’’ one reactant on the surface to another
ials required in operation, the contractor, the architect, a
that is ‘‘in situ’’ is the issue. This may involve an elaborate
landscape architect, a water rights expert, a limnologist, secur-
scheme, in which the ‘‘transport’’ is by convection and diffu-
ity advisor, accountant, financing expert, etc. Those in the
sion. An example is the practice of punching the ground
team involved depend upon the size of project and its context.
surface with a grid of holes used to pump water with a
As a rule, these ideas are learned by the engineer ‘‘on-the-
‘‘reactant’’ to the site of adsorbed (on soil) or dissolved (in
job.’’ Academic courses tend to focus on technical factors,
pore water) contaminants. The ‘‘reactant’’ may be a bacterial
albeit there are exceptions (see, e.g., Qasim et al., 2006).
species (perhaps genetically modified), chemicals, air, steam,
Excerpts from an article by Lagnese (2000), a former presi-
etc. The point is that the ‘‘reactor’’ is the in situ site of the
dent of the Water Environment Federation (1968–1969), and
contaminant; actually, it is one of numerous micro-reactors.
of the American Academy of Environmental Engineers
(1991), who taught a practical design course at the University
1.5 DESIGN of North Carolina, provide a firsthand design perspective.
Notes from Joseph F. Lagnese, Jr.
A variety of nontechnical issues are a part of any design. Some
are addressed in this section. The technical design itself is not
Design is an arduous, iterative process. Ideas are advanced
just a computational algorithm, but involves mostly assump- based upon limited factors and intuition and then evaluated.
tions, judgments, and decisions. An engineering background The initial ideas are then refined and=or eliminated, new ideas
gives the technical basis for decision-making, e.g., what may proposed, and the process repeated as often as necessary to
be feasible, and a context for continued learning. ultimate completion. Stated in another way, design is inher-
ently a ‘‘two steps forward, one step backward’’ process. . . .
the ultimate products of design are the plans and specifica-
1.5.1 FACTORS:NONTECHNICAL tions required to guide the construction of a total facility that is
efficient in operating needs and performance capability.
The end product of the design process is a physical plant. The
Whereas process design theory and fundamentals require
plant design is designed by a consulting engineering firm with mathematical and science capabilities, the other aspects of
qualified staff. The firm selected is usually one of several who design rely upon creative and organizational talents and
may have competed for the contract. Based upon the design, a team-play ability, as well as aptitudes in such diverse areas
contractor is selected, with the engineer acting as the owner’s as economics and aesthetics. Design is a knowledge intensive
agent (the traditional arrangement). Getting to the point of a process which requires not only an understanding of many
completed design involves a host of issues that may involve diverse fundamental concepts, but also such practicums as
politics, dealing with neighbors, financing, owner’s ideas, engineering pricing, selection of process equipment
operation, esthetics, environmental considerations, water and construction materials, architecture, construction tech-
niques and procedures, operational requirements, ergonomics,
rights, etc. The consulting engineer manages these factors
satisfying relevant regulatory controls, and project financing.
based upon experience and exercise of judgment, as opposed
As such, design is an optimization process dependent on the
to academic studies.
appropriate consideration of a broad range of impacting fac-
tors. There are few absolutes; most completed designs repre-
1.5.1.1 Operation Issues sent imperfect solutions.
Design involves a stream of decisions involving ‘‘trade-offs’’
between capital cost and operation. Operation factors may 1.5.1.3 Expansion
include costs, such as energy and maintenance, the ease of The provision for expansion may be done by sizing pipes and
operation, environmental impacts, etc. In addition to such the procurement of land for a projected ultimate build-out.
factors, operators nearly always have views that may be Not to plan ahead may result in several largely independent
important in the design. Some examples include adding a plants on one site, each with its own idiosyncrasies of oper-
gullet with drain in a pipe gallery for easy hose-down and ation, not to mention inordinately higher costs.
cleaning; using aluminum hand rails so that painting is not
required; venting enclosed spaces and rooms that may be 1.5.1.4 Esthetics
handling chemicals; dehumidifying a pipe gallery; providing Esthetic issues are as important as the functional design, and are
attractive lunchrooms and locker rooms with showers; taking often overlooked. Does the plant enhance its sight? Does it fitthe