15 DAFT Shutdown SOP

Short Term DAFT Shutdown:  If the DAFT is to be taken offline for a relatively short period of time, the following SOP may be performed.

1.     Turn off Dissolution System.

a.     Reduce the pressure from the back pressure valve {tag no. 1502VLV5687C}.  The valve is located at the exterior base of the DAFT structure near the bottom of the stairs. This reduces the strain on the Dissolution System Pump Motors {tag nos. 1502PMP5100, 1502PMP5100A, 1502PMP5200, 1502PMP5200A & 1502MTR5100A, 1502MTR5200A} and will make start up much easier when the system is put back online. If the DAFT feeds (WAS, Primary Scum and Secondary Scum) are turned off before the Dissolution System is shut down, the Dissolution System Pumps will air-lock and run dry.

2.     Isolate Feeds to DAFT

a.     Turn off WAS flow to the DAFT.

                      i.        Turn off the WAS pumps {tag nos. 1205PMP2100 & 1205PMP2200}.

                     ii.        Lock out/tag out the pump.

                    iii.        Close the WAS Suction Isolation Valves {tag nos. 1205VLV2100 & 1205VLV2200}.

                    iv.        Close the WAS Discharge Isolation Valves {tag nos. 1205VLV2100A & 1205VLV2200A}.

b.     Turn off Primary Scum flows to the DAFT.  Primary Scum pumping can be shut down for up to 3-4 days.

                      i.        Turn off the Primary Scum Pumps {tag nos. 1103PMP1100 & 1103PMP1200}.

                     ii.        Lock out/tag out the pump.

                    iii.        Close the Primary Scum Suction Valves {tag nos. 1103VLV1100 & 1103VLV1200}..

                    iv.        Close the Primary Scum Discharge Valves {tag nos. 1103VLV1100A & 1013VLV1200A}.

                     v.        Turn off the Primary Scum Skimmers {tag no. 1101COL1171 & 1101COL1172}.

c.     Turn off Secondary Scum Pumping to the DAFT.  Secondary Scum pumping can be shut down for up to 3-4 days.

                      i.        Turn off the Secondary Scum Pumps {tag no. 1207PMP2100 & 1207PMP2200}.

                     ii.        Lock out/tag out the pump.

                    iii.        Close the Secondary Scum Suction Valves {tag nos. 1207VLV2679 & 1207VLV2679A}.

                    iv.        Close the Secondary Scum Discharge Valves {tag nos. 1207VLOV2100A & 1207VLV2200A}.

                     v.        Turn off the Secondary Scum Skimmers {tag nos. 1203COL2171 & 1203COL2172}. The Sludge Collector {tag no. 1203COL2161 & 1203COL2261} can remain in operation.

d.     Turn off the Polymer Feed to the DAFT.

                      i.        Close the DAFT Polymer Feed Suction Valve {tag no. 1502VLV5671}.

3.     Turn off TSPS Pump. The pump is normally controlled by levels in the wet well.

a.     Turn off TSPS Pump #1 {tag no. 1503PMP5100} at the HOA Switch {tag no. 1503HS5100D}.

b.     Lock Out/Tag Out the pump.

4.     Turn off the DAFT Rake.

a.     Turn off DAFT Rake {tag no. 1503RAK/MTR5300} at the HOA Switch {tag no. 1503HS5300}.

b.     Lock Out/Tag Out the Rake.

5.     Turn off the DAFT Automatic Sampler.

a.     Turn off the DAFT Automatic Sampler {tag no. 1502SAMP3151}, which is located at the building exterior.

Long Term DAFT Shutdown:  If the DAFT is to be shut down for more than a couple of days, the following SOP should be performed.  Sludge can be stored in an aeration basin for up to 3 – 4 days.

1.     Turn off Dissolution System.

a.     Reduce the pressure from the back pressure valve {tag no. 1502VLV5687C}.  The valve is located at the exterior base of the DAFT structure near the bottom of the stairs. This reduces the strain on the Dissolution System Pump Motors {tag nos. 1502PMP5100, 1502PMP5100A, 1502PMP5200, 1502PMP5200A & 1502MTR5100A, 1502MTR5200A} and will make start up much easier when the system is put back online. If the DAFT feeds (WAS, Primary Scum and Secondary Scum) are turned off before the Dissolution System is shut down, the Dissolution System Pumps will air-lock and run dry.

2.     Bypass flows to an available aeration basin.

a.     Locate the valve(s) {tag nos. 1201VLV2182, 1201VLV2184, 1201VLV2186, 1201VLV2188, 1201VLV2190} in Gallery 3 that are associated with the aeration basin used for bypass.  Adjust the valve(s) so that flows into the aeration basin are near the SRT target flow.

b.     Monitor the flow and adjust the valve(s) as necessary.

c.     When the sludge level in the aeration basin reaches the top of the air discs, open the Diffuser Air Isolation valve(s) {tag nos. 1201VLV2233, 1201VLV2235, 1201VLV2237, 1201VLV2239, 1201VLV2241} for that aeration basin.   Adding air to the sludge will help maintain a viable biomass and keep the tank from going septic.

3.     Turn off TSPS Pump. The pump is normally controlled by levels in the wet well.

a.     Turn off TSPS Pump #1 {tag no. 1503PMP5100} at the HOA Switch {tag no. 1503HS5100D}.

b.     Lock Out/Tag Out the pump.

4.     Turn off the DAFT Rake.

a.     Turn off DAFT Rake {tag no. 1503RAK/MTR5300} at the HOA Switch {tag no. 1503HS5300}.

b.     Lock Out/Tag Out the Rake.

5.     Turn off the DAFT Automatic Sampler.

a.     Turn off the DAFT Automatic Sampler {tag no. 1502SAMP3151}, which is located at the building exterior.

6.     Pump stored sludge back into the DAFT.  Perform Step 3 when the DAFT is to be put back into service.

a.     Locate the Secondary Scum Drainage valves.  Adjust the valve(s) to pump the stored sludge into the DAFT at a controlled rate.

Drain DAFT Tank:  Perform the following SOP if the DAFT tank needs to be drained, while it is offline.

1.     Drain DAFT Tank.

a.     Locate the isolation valve {tag no. 1502VLV5684} for the DAFT drain line, which is located at the curb between two bollards.

b.     Connect the portable pump and hose to the connection.  Direct the discharge to the nearest sanitary sewer manhole (located nearby in the roadway).

c.     Turn on the pump.  Monitor the volume in the DAFT tank until it is drained.

Record Data to Operator’s Log Book:

1.     Record DAFT Activities to the log book with other entries for the day.  Include the following in the entry:

·         Operator(s) that performed the DAFT SOP.

·         Note condition of equipment, piping, valves, etc.

·         Note any unusual conditions with flows, levels, odors or other process issues.

·         Note any damage, wear, or required maintenance on equipment.