August 2014
Each month, For Practice pulls together sample
questions to help Operators who are preparing for their certification
exam. Listed below are an assortment of practice questions reflecting a
variety of subject matter that Operators may encounter on the exam. The
answers are included below.
Judy Bruenjes, PE
Sr. Env Engineer, Maine DEP
207-287-7806
1. The unit of electrical potential is
a. The coulomb
b. The volt
c. The amp
d. The watt
2.
The aeration basins of a conventional activated sludge treatment system have a
total volume of 250,000 gallons and the MLSS concentration in that tank is
2,650 mg/L. The secondary clarifiers have a total volume of 155,000 gallons and
an average sludge concentration of 5,300 mg/L. The return sludge concentration
is 8,250 mg/L. 4If the operator wants to maintain a 12-day MCRT,
approximately how many gallons of sludge should be wasted? Assume the
effluent TSS is negligible and need not be included in the calculation.
a. 4,200 gallons
b.
2,700
gallons
c. 15,000 gallons
d. 7,000 gallons
3. Which of the following
should always contain a hazard and operability study?
a.
An
emergency plan.
b.
The
annual budget
c.
A
DEP inspector’s report
d.
The
O&M Manual
4.
The most difficult type of solids to remove in a conventional secondary
treatment plant are:
a. Inorganic suspended solids
b. Organic
suspended solids
c. Inorganic
dissolved solids
d. Organic dissolved solids
I want to let you all know that I have hired Judy Bruenjes,
P.E. to join our staff in the compliance and technical assistance
unit. Judy has taken the position formerly held by Dick Darling,
who retired after 22 years of service with Maine DEP. She will be
providing technical assistance, serving as the coordinator for the EPA DMR QA
program, and will serve as the DEP’s point of contact for the Operator
Certification program.
Judy received a B.S. in Engineering from the University of
Michigan and M.S. in Civil Engineering from Northeastern University and is a
Maine licensed Professional Engineer. Previously she provided wastewater
training and consulting services to operators and analysts of municipal and
industrial systems, predominantly in the Southeast. She has also worked
in private industry with storm water treatment and environmental consulting, as
well as with the Mass DEP’s Division of Water Pollution Control.
I am excited to once again be able to provide the MEPDES
license holders with technical assistance when needed. So please feel
free to give Judy a call at 287-7806, or drop her an email at judy.k.bruenjes@maine.gov and let her
know what you need.
Judy is looking forward to working with operators and
analysts to provide skills for improved process control, as well as asset
management, wet weather plans, and lab QA/QC.
Sterling Pierce
Compliance & Technical Assistance
Thanks to all of the dischargers that have participated in
the Department’s recent request for ambient sampling in freshwaters for
phosphorus and nitrogen. We have had a very good participation rate (as
of late August 63% of freshwater dischargers have requested sample bottles from
our contract lab). Even though the flows are higher than we would have
wanted, the information will be very useful. Once we have compiled all
the data, we will be back in touch with all freshwater dischargers to update
them on this issue. We expect that will occur in November.
Brian Kavanah
1.
b. The unit used to designate electrical potential is the
Volt.
2.
c. 15,000 gallons
First
determine the total pounds of sludge in the system (aeration basin + clarifier)
using the “pounds” formula:
Total Sludge = Pounds sludge in
aeration basin + pounds sludge in the clarifier
= (0.25 MG * 2,650 mg/L*8.34) + (0.155 MG * 5,300 mg/L * 8.34) =12,377lb
Next,
use the MCRT formula to determine the pounds of sludge that must be wasted per
day:
MCRT
= Total sludge in system/Total sludge removed from the system per day
The total sludge
removed from the system includes wasted + effluent TSS. However since the
effluent
TSS is very low,
we can assume zero for this problem. So the MCRT formula becomes:
MCRT
= Total sludge in system/Total sludge wasted per day
Rearrange
the MCRT formula to solve for Total pounds of sludge wasted per day:
Total
pounds of sludge wasted per day = Total pounds of sludge in
system / MCRT
= 12,377 lb / 12 days
= 1031 lb/day
Not
quite done yet. The question asks for gallons wasted per
day. How do we convert from lb/day to gal/day?
Since
we know the return sludge concentration (8,250 mg/L) we can determine the
gallons of sludge, again using the pounds formula:
Pounds = flow (MGD) *
concentration (mg/L) * 8.34
Rearrange
to solve for
flow:
Flow = pounds / concentration / 8.34
= 1031 lbs / (8,250
mg/L * 8.34) = 0.015 MGD
=
15,000 gal/day
Phew!
The answer is 15,000 gallons per day must be wasted.
3.
a. the hazards and operability study determines which units in the plant
are susceptible to different hazards (such as flooding, earthquake, hurricanes,
etc.) and how the loss of those units will affect the operability of the
facility as a whole. This study is an important part of any emergency
plan.
4. c. Organic dissolved solids and organic suspended solids are absorbed and
adsorbed by the microbes in a secondary treatment system and removed when those
microbes settle out of the effluent. Suspended inorganic solids usually
settle very quickly and are also removed from the effluent. Inorganic
dissolved solids are not readily taken up by microbes and do not settle out of
the effluent and, therefore, are more likely to pass through a conventional
biological treatment system without being removed.
We have three water related vacancies we are working to
fill:
· * one permit writer position vacated by Cindy
Dionne in Augusta;
· * one inspector position vacated by Stacy Beyer in
Bangor;
· * and one water quality engineer position vacated
by Peter Newkirk in Augusta.
We hope to have these positions filled soon.
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