City and Borough of Juneau
155 S. Seward Street
Juneau, Alaska 99801
tel. 907-586-5240
fax 907-586-5385
http://www.juneau.org

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Wastewater Utility Division

Mendenhall Plant Design Capacity Specifications:

BAR SCREENS:
One 4' (wide) x 19' (high) mechanical bar screen with 1/4" clear opening between bars. The capacity of the bar screen is 12 Million Gallons per Day (MGD) with a maximum water level in the channel of four feet.

One 4' (wide) x 4' (high) manual bar screen with 1" clear opening between bars.

Chemical Additives and Dosages--
Lime is applied to the mechanical bar screen screenings as necessary to stabilize it (inhibit bacterial composition and inactive pathogenic organisms). The typical dosage is 0.1 to 0.15 pound Ca(OH)2 per pound of dry solids with a dosage time of 30 minutes.

Lime System--
The tank capacity is 350 gallons with a 3/4 hp mixer motor. The metering pump is a 1 hp 50 gallons per hour (GPH) at 92 feet Total Dynamic Head (TDH), 0-100% capacity.

INFLUENT PUMP STATION:
Five (5) 50hp pumps with a capacity of 2100 Gallons Per Minute (GPM) at 64 TDH.

GRIT REMOVAL:
Three (3) 4 MGD Centrifugal Grit Removal Systems. The systems have a removal rate of 95% of all grit 100 microns or larger. Dewatered grit will contain less than 15% unattached organic material by weight.

One (1) 1/4 hp motor Grit Dewaterer with a capacity of 1-10 cubic yards per hour.

LIME SYSTEM:
One (1) 3/4 hp mixer motor with a tank capacity of 350 gallons. The metering pump is a 1 hp 50 GPH at 92 feet TDH, 0-100% capacity.

SPLITTER BOX FLOW CHARACTERISTICS:

SBR (MGD)
0.00
0.87
2.10
3.63
5.43
7.44
7.97

ABF (MGD)
0.73
1.11
1.45
1.91
2.65
3.33
3.51

Flows (MGD)
0.73
1.98
3.55
5.54
8.08
10.77
11.48

SEQUENCING BATCH REACTORS:
Eight (8) 62' (long) x 28' (wide) reactors with and operating depth of 14'-24'. The maximum volume (24' operating depth) is 311,650 gallons, with a value of 181,780 gallons at the 14' operating depth. Maintained Volume (activated sludge) is 111,300 gallons. The maximum throughput per reactor batch is 200,347 gallons.

SBR BLOWER:
Nine (9) 60 hp axial flow rotary lobe SBR Blowers with a capacity of 300-1000 standard cubic feet per minute (scfm); eight (8) variable-speed, electric-driven and one (1) variable-speed, gas-driven digester. Inlet pressure equals 14.4 psin; discharge pressure is 9.5 pressure per square inch gauge (psig). Inlet temperature is 80F and discharge is 215F. The speed of the blowers is 1200 to 2700 rpm with a variable frequency drive controller. The Digester Gas Engine is 112 brake horse power (Bhp) intermittent at 2200 rpm. Oxygen Transfer is 945 kg 02/hour at 16' water depth.

JET MIX PUMPS:
Eight (8) 35 hp submersible, centrifugal, non-clog, sewage-handling pumps. The capacity is 4800 gpm at 20' TDH.

WASTE SLUDGE PUMPS:
Eight (8) 15 hp submersible, centrifugal, non-clog, sewage-handling pumps with a capacity of 900 gpm at 40' TDH.

BLOWERS:
Two (2) 25 hp axial flow rotary lobe blowers with a capacity of 300 cfm; one (1) electric-driven and one (1) gas-driven digester. The speed of the blowers is 1850 rpm. The inlet pressure is 14.4 psig and discharge pressure is 12 psig. Inlet temperature is 80F and discharge is 240F. The Digester Gas Engine is 71 Bhp intermittent at 2200 rpm.

AIRLIFT PUMPS BLOWER:
One (1) 40 hp blower with a 250 scfm capacity. Inlet temperature is 80F and discharge is 260F. Inlet pressure is 14.4 psia, with a discharge pressure of 20 psig. The speed of the blower is less than 3600 scfm.

WASTE SLUDGE JET PUMP:
One (1) 35 hp submersible, centrifugal, non-clog, sewage-handling pump with capacity of 4800 gpm at 20' TDH. 15 hp pump with a capacity 900 gpm at 40' TDH.

Waste Sludge Storage:
One (1) 62' (long) x 21' (wide) x 25' (high) basin with a maximum volume of 243,474 gallons.

THICKENED SLUDGE JET PUMP:
One (1) 35 hp submersible, centrifugal, non-clog, sewage-handling pump with a capacity of 4800 gpm at 20' TDH.

Thickened Sludge Storage:
One (1) 62' (long) x 21' (wide) x 25' (high) basin with a maximum storage capacity of 243,474 gallons.

CENTRIFUGE:
One (1) 100 hp centrifuge with the following capacity: (a) feed sludge concentration of 0.5% to 1% TSS; (b) capture 805 of suspended solids; (c) flow 90-150 gpm; (d) no coagulant; and (e) cake -4% to 5% total solids.

Centrifugal Feed Pumps: Two (2) 6 hp submersible, centrifugal, non-clog, sewage-handling pumps with a capacity of 150 gpm at 45' TDH.

DECANTERS:
Four (4) per basin for a total of 32 decanters, each with an average capacity of 2600 GPM (Gallons Per Minute).

DIGESTER FEED PUMPS:
Two (2) self-priming, air-operating diaphragm with a capacity of 50 gpm at 120' TDH.

CHLORINATORS:
Two (2) remote-vacuum arrangement chlorinators with a capacity of 1000 lb. per day each. The feed rate is automatically adjustable over a 20:1 range.

SULFONATORS:
Two (2) remote-vacuum arrangement sulfonators with a capacity of 400 lbs per day. The feed rate is automatically adjustable over a 20:1 range. Operating water conditions: (a) back pressure: 5.0 psig at injector; (b) supply water: 50 gpm at 60 psig.

JET CHLORINE INJECTION SYSTEM:
Two (2) 5 hp jet chlorine injection systems. The capacity for each system is instantaneous flow between 2.6 MGD and 12.5 MGD with design flow of 6 MGD.

OPERATING PARAMETERS:
MLVSS =0.7 MLSS; MLSS set at 2500 mg/1 when vessel is at "full" set point. "Full" set point is at 14' for average daily flow and design conditions.
F/M =0.23 at average daily flow and design conditions.
pH =6-8
D.O. =0-4 mg/1 depending on phase cycle.
Detention Time (Batch Cycle Time) =3.6 hours.

REMOVAL EFFICIENCY:
BOD: 90%
S.S.:90%

 



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