Hach-Lange SD900 User Manual - Manual (Page 35)

5. Enter the time (24-hour format) and date for the first stop time.
6. Continue to add start and stop times as necessary.
Collect first flush stormwater samples
The stormwater option collects first flush (FF) samples or initial runoff during storm conditions when
pollutants are typically at high concentrations. The first flush samples are collected at timed intervals
and can be started by an external device. A stormwater program can operate at the same time as the
main program. First flush samples are usually collected within 30 minutes of a storm. The stormwater
program has these capabilities:
• Collect grab samples at up to 24 different time intervals. First flush and main program flow-
weighted composite samples are automatically segregated. The first flush sample volume may be
set independently of the sample volume for the flow-weighted composite.
• Initiation by an external device. A dry contact closure across pins B and D on the auxiliary
connector, held closed for at least 61 seconds, is necessary.
• For multiple bottles, the sampler can be programmed to collect one large “first flush” sample (or
small multiple samples) at timed interval(s). The number of bottles segregated for the first flush
sample is selectable. Concurrently, flow-weighted samples are collected from the beginning of the
storm until all remaining bottle(s) are filled, or after a specified time has elapsed.
Note: NPDES requirements typically requests that the first three hours of a storm be monitored. If the flow volume
is lower than expected, flow-weighted sampling can continue for a long time as the flow rates decrease and the
sample intervals become longer.
1. Go to PROGRAM SETUP>MODIFY SELECTED>ADV SAMPLING.
2. Select STORMWATER>ENABLE.
3. Select how the program will start.
Option Description
Immediate The user starts the sampling program.
External The sampling program starts when a signal is received by an external device.
4. If configured for a single bottle, enter the number of first flush (FF) samples to collect.
5. If configured for multiple bottles, enter the number of bottles to be used for first flush collection.
6. Enter the multi-bottle distribution mode.
• Samples per bottle—more than one sample is collected in each bottle
• Bottles per sample—more than one bottle is used to collect each sample.
7. Enter the number of samples per bottle or bottles per sample.
8. Enter the time interval between each first flush sample cycle. The intervals can be different. The
sum of the intervals is equal to the total length of the stormwater collection period.
Note: The number of intervals is determined by the number of bottles and the distribution mode.
9. Enter the volume of each first flush sample.
10. Select whether a time limit will be used.
Option Description
ENABLE The sampling program stops after a specified time. Enter the time.
DISABLE The sampling program operates until the program is complete.
Set variable intervals
Variable time intervals (hours and minutes) or flow intervals (counts) can be set for sample cycles.
Variable intervals cannot be enabled when CTVV is enabled.
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