M ost see wastewater treatment as a necessary
evil to keep watercourses clean
and safeguard human health. While cleaning
water for reuse is green indeed, the treatment
process is not. Processing wastewater requires
large amounts of energy, toxic chemicals,
and produces waste solids for disposal.
Recently some have recognized hidden
environmental benefits for these processing
"evils". One of these twists is taking
place in Delhi Township, Michigan,
where modifications to the wastewater
treatment plant are incorporating "green"
systems. HRC has completed the design
and begun construction of this firstof-
a-kind system that may revolutionize
wastewater solids (residuals) treatment.
This project involves changing Delhi's current
residuals treatment practice to a twostage
digestion process. The new system,
which takes place in closed tanks without
oxygen, incorporates a thermophilic (hotter)
stage and a mesophilic (warmer) stage which
produces Class A biosolids; that is, solids
that are suitable for direct application to farm
fields and gardens without further treatment.
Thus, the soil conditioning and nutrient content
of these solids might be beneficially used.
In partnership with HESCO, who will
provide the digestion process, even more
"greening" will be achieved. Methane gas
produced by the process will be used to
power microturbines and produce electricity
for use at the Plant. The exhaust heat
from the turbines will in turn be used to
heat the digesters; closing the energy loop
on wastewater residuals treatment. This
system is known as "Combined Heat and
Power" and Delhi's is the first in Michigan.
Another unusual aspect of this project
is performance specifications were prepared
for the entire system instead of
its individual components because of
the goal to produce Class A biosolids.
The complex piping was designed using 3-
D software to minimize interferences and to
provide better images of the system. These
improvements are being constructed by
Irish Construction, who was excited to be
able to participate in this "green" initiative.
Encouragement for the project came from
Delhi Township officials including Supervisor
Stuart Goodrich, Treasurer Harry
Ammon, Clerk Evan Hope and Trustees
John Hayhoe, Jerry Ketchum, Paul
Krepps, and Roy Sweet. Also, Township
Manager John Elsinga and Director of
Public Services Sandra Diorka have had
active roles in implementing this project.
So what does this have to do with water?
The answer is anything that can help to
operate wastewater systems in an environmentally-
friendly manner, and anything
that can make byproducts from the treatment
process useful, and anything that
can help with energy reduction is worth
a closer look. In this case, the technology
that is now available, in combination with
a far-seeing Township, is helping to create
a "greener" wastewater treatment plant. ±
http://www.hrc-engr.com/Pubs/HRC_ByDesign_Spring_08.pdf
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