wastewater grade 1 exam
domestic wastewater Ans- Comes from schools, homes, hospitals, businesses, light industrial facilities.
population equivalents Ans- 100 lbs wastewater per day, .2 lbs TSS/day, .17 BOD/day
industrial wastewater Ans- Comes from industries. Compatible wastes can be processed by the plant.
Incompatible wastes are toxic to the plant.
sanitary wastewater Ans- The combined domestic and industrial waste waters from community.
storm water Ans- Water that runs off roads, parking lots, and other impervious surfaces during rain and
snow storms
sanitary sewers Ans- Convey domestic and industrial waste waters, typically from where they are
generated to the plant.
storm sewers Ans- Convey storm water, typically from storm drains directly to a point of discharge
(stream, river, ocean).
combined sewers Ans- Convey sanitary waste water combined with storm water.
Reasons to collect samples Ans- federal and state regulatory compliance, process control, trouble
shooting, special studies including future designs.
grab sample Ans- One time sample. Chlorine residual, coliform tests, settable solids, dissolved oxygen,
pH, grease and oil, sulfide tests.
Time based composite sample Ans- Fixed volume of sample is collected after passage of a set amount of
time over a certain time period.
, Flow based composite sample Ans- Fixed volume of sample is collected after a prescribed amount of
flow has passed through the sampling point, or a volume of sample proportional to the flow is collected
after passage of a prescribed amount of time over a certain time period. This sample can also be called a
flow proportional composite sample.
diurnal flow Ans- Low at night between 2 and 5 am, steady steep increase in flow starting after 5 am,
reaching first peak in the late morning or early afternoon, slight decrease through the afternoon, second
peak between 6 and 9 pm, and a tapering off of to the low flows of 2 am.
BOD Ans- Depletion of dissovled oxygen in a sample over 5 days at 20c is measured. Direct measure of
the amount of dissolved oxygen consumed by aerobic bacteria over five days, indirect measure of the
organic strength of waste water, used to asses the performance of WTP and the unit operations and unit
processes used in WTP.
COD Ans- This test involves the chemical oxidation of all organics in a sample. Measure of organic
strength of waste water, COD is always greater than BOD, In raw municipal sewage COD is typically 2 to
4 times greater than BOD, takes 2 hrs to run COD compared to 5 days for BOD therefore more
appropriate for process control.
pH Ans- The log of the reciprocal of the the hydrogen ion concentration. PH 6 is 10 times the hydrogen
ion concentration of 7. 5 is 100 times the conc of ph 7.
Total solids Ans- TSS + TDS
Settleable solids Ans- All settleable solids are TSS but not all TSS are settleable.
Hydrogen sulfide h2s Ans- Toxic, flammable and explosive, rotten egg odor, dulls sense of smell,
paralyzes ability to breath, corrosive, heavier than air collects in low lying areas.
Methane ch4 Ans- Anaerobic digester have 62-70% methane vol basis. Lel is 5% and uel is
15%.flammable/ explosive. Odorless, not toxic but can asphyxiate at high conc, lighter than air.
Anaerobic digester gas Ans- 65% methane, 34% carbon dioxide, 1% other inert gases. Contains less than
1% h2s
domestic wastewater Ans- Comes from schools, homes, hospitals, businesses, light industrial facilities.
population equivalents Ans- 100 lbs wastewater per day, .2 lbs TSS/day, .17 BOD/day
industrial wastewater Ans- Comes from industries. Compatible wastes can be processed by the plant.
Incompatible wastes are toxic to the plant.
sanitary wastewater Ans- The combined domestic and industrial waste waters from community.
storm water Ans- Water that runs off roads, parking lots, and other impervious surfaces during rain and
snow storms
sanitary sewers Ans- Convey domestic and industrial waste waters, typically from where they are
generated to the plant.
storm sewers Ans- Convey storm water, typically from storm drains directly to a point of discharge
(stream, river, ocean).
combined sewers Ans- Convey sanitary waste water combined with storm water.
Reasons to collect samples Ans- federal and state regulatory compliance, process control, trouble
shooting, special studies including future designs.
grab sample Ans- One time sample. Chlorine residual, coliform tests, settable solids, dissolved oxygen,
pH, grease and oil, sulfide tests.
Time based composite sample Ans- Fixed volume of sample is collected after passage of a set amount of
time over a certain time period.
, Flow based composite sample Ans- Fixed volume of sample is collected after a prescribed amount of
flow has passed through the sampling point, or a volume of sample proportional to the flow is collected
after passage of a prescribed amount of time over a certain time period. This sample can also be called a
flow proportional composite sample.
diurnal flow Ans- Low at night between 2 and 5 am, steady steep increase in flow starting after 5 am,
reaching first peak in the late morning or early afternoon, slight decrease through the afternoon, second
peak between 6 and 9 pm, and a tapering off of to the low flows of 2 am.
BOD Ans- Depletion of dissovled oxygen in a sample over 5 days at 20c is measured. Direct measure of
the amount of dissolved oxygen consumed by aerobic bacteria over five days, indirect measure of the
organic strength of waste water, used to asses the performance of WTP and the unit operations and unit
processes used in WTP.
COD Ans- This test involves the chemical oxidation of all organics in a sample. Measure of organic
strength of waste water, COD is always greater than BOD, In raw municipal sewage COD is typically 2 to
4 times greater than BOD, takes 2 hrs to run COD compared to 5 days for BOD therefore more
appropriate for process control.
pH Ans- The log of the reciprocal of the the hydrogen ion concentration. PH 6 is 10 times the hydrogen
ion concentration of 7. 5 is 100 times the conc of ph 7.
Total solids Ans- TSS + TDS
Settleable solids Ans- All settleable solids are TSS but not all TSS are settleable.
Hydrogen sulfide h2s Ans- Toxic, flammable and explosive, rotten egg odor, dulls sense of smell,
paralyzes ability to breath, corrosive, heavier than air collects in low lying areas.
Methane ch4 Ans- Anaerobic digester have 62-70% methane vol basis. Lel is 5% and uel is
15%.flammable/ explosive. Odorless, not toxic but can asphyxiate at high conc, lighter than air.
Anaerobic digester gas Ans- 65% methane, 34% carbon dioxide, 1% other inert gases. Contains less than
1% h2s
