CE3503 – Environmental Engineering - Field Trip #2
C&EE Environmental Process Simulation Center
This field trip will be to the C&EE Environmental Process Simulation Center (EPSC),
located in Room 106 of the Dow Environmental Science & Engineering Building. The
EPSC was designed to provide students with hands-on experience in working with
environmental processes. A number of upper division undergraduate and graduate
classes conduct experiments in the facility. Please visit –
http://www.cee.mtu.edu/environ_proc_sim_center.html
prior to the field trip to learn more about the EPSC.
In this field trip, we will use the EPSC to provide a demonstration of a typical process
train for drinking water treatment. We will begin with a raw water source and proceed
through six unit operations.
RAW WATER 
The raw water supply is derived from the Keweenaw Waterway and spiked with clay and
food coloring to permit better visualization of the treatment process.
COAGULATION  FLOCCULATION  SEDIMENTATION 
We will apply a bench scale jar test in which a chemical (coagulant) is added to the water
in a ‘flash-mix’ and then agitated slowly (flocculated) to permit the formation of larger,
more easily settled particles (flocs).
We will then shut off the mixers and allow the flocs to settle out. Note that, while the
water has become much clearer, significant cloudiness remains. We will demonstrate this
by comparing turbidity measurements before and after settling. It is then necessary to
remove the residual turbidity through filtration.
FILTRATION 
We will pass the water through a multi-media filter containing anthracite, sand and
gravel. The goal in filtration is to remove large particles at the top of the filter and
progressively smaller particles as we move deeper into the bed. Anthracite is used at the
top because this medium has large pores and thus captures only large particles. Sand is
used next to capture smaller particles. Gravel serves as the base of the multi-media
system and keeps the sand from moving out with the filtered water. The densities of the
component media are such that they will re-sort as intended during backwashing (even
though the anthracite medium has a larger diameter than the sand medium). We will
evaluate the effectiveness of this treatment through additional turbidity measurements.
ADSORPTION 
At this point we have been quite successful in removing particles, but have made little
progress with color, a surrogate for potentially dangerous dissolved organic chemicals.
We will remove these by passing the water through an activated carbon column. Note the
reduction in color in the effluent.
DISINFECTION 
Finally, the water is disinfected through the addition of chlorine. Here, we will use
household bleach. The chlorine kills bacteria, protozoa and viruses through direct
oxidation, i.e. it ‘burns them up’. In addition, chlorine oxidizes any dissolved organic
matter remaining in the sample. Where large amounts of dissolved organic matter are
present, much of the chlorine may be consumed and disinfection may be incomplete.
Further, we need to maintain a residual to pass along to the distribution system. We will
test for chlorine residual to insure that we have a safe water supply.
NOTES:
A Drinking Water Treatment Process Train
Martin T. Auer – MTU Civil & Environmental Engineering
Our demonstration of a drinking water
treatment process train will be held in the
Environmental Process Simulation Center, a
teaching facility to supplement the unit
operation theory learned in class. This oneof-a-kind facility provides students with
hands-on opportunities to explore bench
and pilot-scale processes for water
treatment, wastewater treatment and air
pollution control.
Drinking water treatment seeks to make a water supply both potable (safe) and palatable (goodtasting) by removing pathogens (disease-causing organisms) and particles (that might shield
pathogens from disinfection.
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
This is accomplished through a process train that includes coagulation, flocculation,
sedimentation, filtration and disinfection.
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
In coagulation, aluminum sulfate (alum) is flash-mixed with the raw water. The aluminum ions
form positively-charged hydroxy-metallic complexes that neutralize the negative charges of clay
particles allowing them to clump together (coagulate) into larger, more easily sedimented flocs.
The complexes also encourage floc formation by bridging.
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
In flocculation, the water is gently mixed encouraging particle contact and building larger flocs.
The mixing rate is reduced as the water moves through a series of flocculation units to avoid
breaking up the large particles.
A Drinking Water Treatment Process Train
→
→
Untreated
Water
Treated
Water
Coagulation
Flocculation
Sedimentation
Filtration
Disinfection
In sedimentation, particles settle to the bottom of a tank and are removed to waste. It is not
efficient to remove all particles in this way because small particles settle very slowly and thus an
immense sedimentation tank would be required.
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
The water is then passed through a rapid sand filter to remove the remaining particles.
After a period of operation, the filtration apparatus becomes clogged and must be
backwashed.
In this drinking water treatment
demonstration, we are adding removal of
organic chemicals by adsorption with
granular activated carbon.
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
→
→
Untreated
Water
Coagulation
Treated
Water
Flocculation
Sedimentation
Filtration
Disinfection
The final step prior to distribution is to insure that all pathogens have been destroyed and
that residual disinfectant is present to protect the distribution system. This disinfection is
typically accomplished by the addition of chlorine.