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SECTION 12:
Waste Management - Anaerobic Digestion
12.1 Introduction
This section presents the design bases for anaerobic digestion facilities in one phase, to be incorporated into the future
installations of the Wastewater Treatment Plant PTAR Las Esclusas. Likewise, reliability, redundancy and design
criteria, as well as functional and process descriptions, are included for each unitary solids management process.
12.2 Anaerobic Digestion in a Phase
One-stage anaerobic digestion facilities will serve to digest the thickened primary sludge, as well as concentrated
primary foams, creams, fats and oils (FOGs). The digestion is used to biologically stabilize the sludge, reducing the
mass of solids for disposal. This process produces methane for the generation of energy, increases the concentration
of dehydrated sludge cake and reduces its odor, reducing the attraction of vectors, and decreasing pathogen levels in
biosolids.
There are three streams that feed the anaerobic digestion facilities: thickened primary sludge, concentrated foam from
the primary clarifiers and thickeners, and FOG present in the incoming stream to the PTAR. Table 12-1 summarizes
the characteristics and loads of the three streams mentioned, as well as those of the incoming feed mixture to the
digestion facilities, under dry and wet climate conditions.
12.2.1 General description
Three new digesters will be built for the handling of solids, with the necessary provisions for the construction of a fourth
digester in the future. Three new digesters will be built for the handling of solids, with the necessary provisions for the
construction of a fourth digester in the future. The four digesters will be designed with the same dimensions and
hydraulic characteristics. These digesters will have an operating temperature of 35oC, and under wet weather
conditions they will provide a 20-day Solid Retention Time (SRT), with one of them out of service. Likewise, the
digesters will comprise a mixing system, to promote the digestion process. The fully digested mesophilic sludge will be
transferred to the digested sludge storage tank for its further dehydration.
12.2.2 Reliability and Redundancy Criteria
•
The SRT of the digestion process is about 20 days in wet weather conditions, with a digester out of service.
Likewise, said SRT is approximately 30 days in humid climate conditions, with all digesters in service. In this
way, a stable operation of the digesters and a greater degradation of volatile solids (VS) will be ensured,
maximizing gas and energy production.
•
All pump systems will have a stand-by pump.
12.2.3 Design Criteria
By means of the anaerobic digestion process the SVs are destroyed, resulting in a reduction in the total mass of the
sludge solids. Table 12-2 summarizes design and performance criteria as well as loads.
Each digester will be equipped with a system for the complete mixing of its contents, in order to standardize the
temperature and eliminate short circuits. Likewise, the digesters system will have pumps for the transfer of the digested
mesophilic sludge to the digested sludge storage tank, for its subsequent dehydration. The design criteria for the mixing
system and the pumps are presented in Table 12-3.
Chart 12-3
Mixing Design Criteria for Digesters and Sludge Transfer
Parameter
Value
Digester Mixing System
Number
Type
3 (1 for each digester)
Pumping Mix
Mixing Assembly
Type
- Floor Mounted Mixing Mouthpieces
- Foam spray nozzles mounted on the wall
Total number of nozzles per tank
8 mounted on the floor
8 mounted on the wall
Mixing pumps
Number of units per digester
2 (1 operating, 1 in stand-by)
Type of pump
Horizontal Centrifuge Crusher
Solids concentration (%ST)
2.5% - 3%
Design capacity (m3/hr)
1135
Total dynamic head - TDH (m)
12.2
Maximum Pumping Speed (rpm)
1200
Maximum Motor Power (kW)
Motor Drive Type
57
Constant speed
Digestion Mesophilic Sludge Transfer
Pumps
Number of units
Type of pump
Solids concentration (%ST)
3 (2 operating, 1 in stand-by)
Progressive Cavity
0% - 6%
Design capacity (m3/hr)
91
Total dynamic head - TDH (m)
15
Maximum Pumping Speed (rpm)
350
Maximum Motor Power (kW)
15
Motor Drive Type
Constant speed
Transfer Pump Crushers
Number of units
3
Type of pump
100
Design capacity (m3/hr)
91
Maximum Motor Power (kW)
3.7
Motor Drive Type
Change of direction of rotation
12.2.4 Description of the Anaerobic Digestion Process
The thickened sludge pumps located in the primary sludge thickener building will transfer the thickened primary sludge
to the digesters. The concentrated primary foams will be pumped into the thickened primary slurry piping at a point
prior to the digestion facilities. The FOGs will have a feed line to the independent digesters, due to their pre-heating.
The feed slurry mixture will be evenly distributed to the 3 diggers of 5,000 m3 each. These digesters will have a pumping
mixing system comprising horizontal crusher pumps, suction and discharge piping as well as a high speed nozzle
arrangement designed to provide a complete mixture of the contents as well as entrainment of any foam. For each
digester a crusher pump will be provided in operation and another in stand by. On the other hand, 3 progressive cavity
pumps (2 in operation and 1 in stand-by) will be provided for the transfer of digested mesophilic sludge from the
digesters to the digested sludge storage tank.
12.2.5 Description of Operation
The sludge feed pumps will start or stop based on the conditions of the primary sludge thickening facilities.
Concentrated foam pumps will start only when thickened primary sludge flows into the digesters. The incoming flow to
the digestion facilities will be monitored by means of a magnetic flow meter; And each of the digesters will have a
motorized valve in charge of distributing the thickened mixture of primary sludge, as well as concentrated primary
foams, in an equitable way among the digesters in operation.
Because the FOGs will be pre-heated prior to entering the digesters, to assist in handling and pumping, they will have
a magnetic flowmeter and independent motorized valves for equitable distribution among the digesters in operation.
On the other hand, the mixing system of the three digesters can operate continuously, or in time intervals. Sufficient
mixing will maximize Volatile Solids Reduction (VSR) and gas production. The digested mesophilic sludge will overflow
into a moist well to maintain a constant level within the digesters. Once the wet pit level reaches the high level set point,
a motorized valve will open and a digested mesophilic slurry transfer pump will start to pump slurries into the digested
sludge storage tank. Also, once the level of the wet pit reaches its low set point, the transfer pump will stop and the
motorized valve will close.
12.2.6 Acquisition Process
The Employer has classified the Anaerobic Digester Mixing System as one of the seven (7) Main Teams of the project.
Accordingly, each Bidder must submit in its bid, the respective documents that demonstrate the mixing system
proposed for the digesters, meets both the criteria described in the Technical Specification, and the criteria of
performance and experience required for the proposed equipment.
The Contractor shall assume responsibility for the complete mixing system of the anaerobic digesters. This system
must be supplied and coordinated through the Contractor, by a single manufacturer. The Contractor must install the
three (3) new anaerobic digestion units with all necessary ancillary equipment. The nominal volume of each digester
will be 5,000 m3. The anaerobic digesters will operate in the mesophilic mode with operating temperatures between 35
°C and 38 °C to treat sedimented primary solids with addition of ferric chloride (20 mg / L at 40 mg / L) and polymer.
The mixing system will be hydraulic with external pumping units and auxiliary piping with nozzles. The pumped mixing
system must deliver at least 7.0 kW / 1000 m3 in the discharge of the nozzles.
Likewise, the manufacturer supplying the mixing system of the anaerobic digesters, through the Contractor, shall
document the mixing operation experience with the same or equivalent equipment in five (5) sites for a period of at
least five (5) years in each.
The Contractor shall review and approve the documents and referrals corresponding to the mixing system of the
anaerobic digesters before awarding the construction contract for the PTAR Las Esclusas.
12.3 Heating System of Digesters
12.3.1 General description
In order to optimize the process of anaerobic digestion, the temperature of the digesters will be maintained at 35 ˚C by
means of a heating system. Accordingly, the sludge contained in the digesters will be circulated through concentric
tube heat exchangers. In this way, the heat of the hot water circulating inside the heat exchanger will be transferred to
the sludge through the wall of the tube containing said sludge, before it is returned to the digester. The water will be
heated by the heat recovered from the routing of the generator motors as well as by means of pyrotubular boilers. To
see the sizing of generators and boilers, refer to Section 13 - Cogeneration, of the Design Bases.
12.3.2 Reliability and Redundancy Criteria
•
The digesters will have recirculation pumps for stand-by sludge.
•
A hot water pump will be supplied from the standby primary circuit.
12.3.3 Design Criteria
Table 12-4 summarizes the design criteria for the heating system of the digesters.
12.3.4 Description of Warming Processes of Digesters
The temperature of the digesters should be maintained at 35 ° C to provide optimum conditions to the mesophilic
bacteria. As mentioned above, maintaining this temperature in the digesters is achieved by feeding and recirculating
the slurry through concentric tube heat exchangers.
Each digester will have its own independent heat exchanger. The recirculation slurry piping shall be configured in such
a way as to enable Digesters No. 1 and 2 to use the heat exchanger of the other digester if necessary. Digester No. 3
and Future Digester No. 4 will have the same functionality
Horizontal centrifugal impeller pumps will be supplied to recirculate the sludge through the heat exchangers. Each
digester will have a separate recirculation pump. Digesters No. 1 and 2 will share a pump in stand-by. Digester No. 3
will have a stand-by pump that will be shared with digester No. 4 in the future.
Hot water will be produced by means of the generator motors and the boiler system, to heat the digesters. The hot
water will be circulated through the digesters by means of the hot water pumps of the primary circuit. The water
temperature will vary between 70 ° C and 90 ° C. Said water will be transported using insulated pipe to minimize heat
loss.
Each heat exchanger will have a separate hot water pump from the secondary circuit, and a three-way temperature
control valve. The hot water pump of the secondary circuit will circulate hot water continuously through the heat
exchanger.
A three-way temperature control valve allows mixing of hot water from the primary circuit with water from the secondary
circuit to maintain the temperature of the latter. As hot water enters the primary to secondary circuit, a same amount of
water with lower temperature exits the secondary circuit to the primary circuit, to be reheated by the generator motors
or the boiler.
12.3.5 Description of the Operation of the Digester Heating System
Heating of the digesters will start with one of the following conditions:
•
The temperature of the digester sludge is lower than the temperature of the lowest set point.
•
The magnetic flow meter installed in the feed line to the digesters indicates presence of flow.
Any of these conditions will initiate the respective recirculation sludge pump for heating, and the hot water recirculation
pumps for the secondary circuit feeding the heat exchanger. Once it is started, the heating system of each digester will
be controlled by the modulation of a three-way valve for temperature control, in order to maintain a temperature set
point in the sludge exiting the heat exchanger. The maximum temperature of the sludge leaving the heat exchanger
should not exceed 40.5 ° C to prevent backflow of sludge into the heat exchanger tubes.
The hot water pump for the primary circuit will operate continuously and the temperature of the primary circuit will be
controlled by the generator motors and the boiler system.
12.4 Digestion Gas Collection and Management System
12.4.1 Abstract
The gas produced through the anaerobic digestion process will be collected from all the digesters in service and stored
in a double membrane gas meter. The stored gas will be processed by a treatment system before being used by the
generator engines and the pyrotubular boiler. Excess gas from digestion will be sent to a tea to be incinerated.
12.4.2 Reliability and Redundancy Criteria
There will be a tea (burner) in stand-by to burn the excess gas in case the operating tea fails or a second tea is required
to burn the excess gas.
12.4.3 Design criteria
The design criteria for the digester gas collection and management system are summarized below in Table 12-5.
12.4.4 Description of Processes of the Digesters Gas Collection System
The dual membrane gas meter has a membrane that increases or decreases the available volume based on the
incoming gas flow of the digesters. The space between the inner and outer membrane is pressurized to 20 mbar using
atmospheric air from a fan in operation and one in stand-by. The pressurized air acts on the inner membrane to maintain
the pressure of 20 mbar for the gas system of the digesters. From storage, the gas is treated and used in the generator
engines. Excess gas is incinerated by means of the teas.
12.4.5 Description of Processes of the Digesters Gas Collection System
All the digested gas will be led first to the membrane gasometer. A level sensor will be installed on the top of the outer
membrane to monitor. The level of the inner membrane, this determines the amount of gas stored. The gas can freely
leave the storage membrane for use in generators and the boiler. When the storage of the digested gas reaches the
capacity limit, a motorized valve opens towards the tea to incinerate the excess gas. Once the storage levels are
lowered to a predetermined level, the motorized valve will close thereby stopping the burning of excess gas.
In the event that a bypass operation is required on the gasometer, in the event that it is necessary to remove it from
service for maintenance operations, the motorized valves in the plugs will open, and the pressure regulating valves in
the plugs will maintain The pressure in the gas digestion system. The teas have an autopilot control to turn on every
time gas from the digesters enters.
12.5 Reception and Storage of Fats and Oils (FOGs)
The proposed FOG reception station will receive, store, heat and equalize the FOG delivered in tank trucks. In this way,
the hot FOGs will be pumped to each of the digesters in operation, and will enter these through the hot sludge return
pipes. It is estimated that the facility will receive about 10 FOG trucks a day. With an average capacity of 3,800 liters in
each truck, it is estimated that approximately 38,000 liters will be received per day.
12.5.2 Reliability and Redundancy Criteria
•
A recirculating crusher pump will be supplied in stand-by for the FOG pumping station.
•
A stand-by power supply pump will be supplied.
12.5.3 Design criteria
Chart 12-6
Design Criteria for the FOG Reception System
Parameter
Value
Truck Unloading
Discharge flow (L/s)
Pretreatment
40-65
Rock Trap
Online Crusher
FOG Elevation Station
Number of units
2 (1 operating, 1 in stand-by)
Type of pumps
Recirculation Crushers pumps
Design capacity (m3/hr)
235
Total dynamic head - TDH (m)
13
Maximum Pumping Speed (rpm)
1200
Maximum Motor Power (kW)
18.8
Motor Drive Type
Constant velocity
Storage Tanks FOG
Capacity (m3)
140
Operating pressure (mbar)
20
Mixing pumps FOG tank
Number of units
Solid concentration (%ST)
Type of pumps
2 (1 operating, 1 in stand-by)
Centrifuges Horizontal Crushers
2.5% - 3%
Design capacity (m3/hr)
235
Total dynamic head - TDH (m)
12
Maximum Pumping Speed (rpm)
Maximum Motor Power (kW)
Motor Drive Type
1200
15
Constant velocity
FOG heat exchangers
Number of units
Type
1
Concentric tubes
Nominal Heat Transfer (kW)
74
Surface Area of Heating (m2)
2.4
Number of Tubes
6
Sludge Flow (m3/h)
34
Hot water flow (m3/h)
34
Recirculation Pumps
Number of units
2 (1 operating, 1 in stand-by)
Type of pumps
Progressive Cavity
Solid concentration (%ST)
2% - 5%
Design capacity (m3/hr)
34
Total dynamic head - TDH (m)
6
Maximum Pumping Speed (rpm)
350
Maximum Motor Power (kW)
5.6
Motor Drive Type
Constant velocity
Secondary Circuit Hot Water Pumps
Number of units
1
Type of pumps
Centrifuge in line
Design capacity (m3/hr)
34
Total dynamic head - TDH (m)
5.5
Maximum Pumping Speed (rpm)
1750
Maximum Motor Power (kW)
0.75
Motor Drive Type
Constant velocity
FOG Feed Pumps
Number of units
2 (1 operating, 1 in stand-by)
Type of pumps
Progressive Cavity
Solid concentration (%ST)
2.5% - 3%
Design capacity (m3/hr)
6.8
Total dynamic head - TDH (m)
15
Maximum Pumping Speed (rpm)
300
Maximum Motor Power (kW)
3.7
Motor Drive Type
Variable
12.5.4 Description of Processes
The station shall be designed to discharge FOG from the tankers in the discharge area by means of air compressors
mounted on the truck or by means of the force of gravity. The discharge area will be melted at the site, particularly nonslip slope to a drainage channel that will collect spills, wash water, and flow by gravity into the FOG sump. The discharge
area will be designed to facilitate the washing of this as well as to contain the spills. The following is a detailed
description of the FOG receiving station process:
•
The inlet pipe of the receiving station shall be equipped with a quick-connect coupling to allow discharge of
the FOG tanks.
•
The FOGs will go through a large-capacity rock trap designed to catch stones. Said operation will be controlled
by a motorized valve located downstream of said rock trap. The FOGs will then pass through a crusher to the
lift station.
•
The FOG lift station consists of two recirculating crushing pumps which will transfer the FOGs to the storage
tank located near the digestion facility.
The FOG storage / equalization tank will be heated and mixed. To heat the FOGs, hot water from the primary circuit
will be pumped through a concentric tube heat exchanger. A progressive cavity independent heat pump and a shredder
will circulate the FOGs in the storage bin by means of the FOG heat exchanger. The setting temperature is 43 ° C. The
storage tank will also be provided with a mixing system with recirculation crushers and nozzles.
There will be two progressive cavity FOG transfer pumps. The pumps will be provided with automatic controls and will
be equipped with frequency inverters, flow meters and pressure transducers. The tank will be provided with a level
transducer that will start and stop the pumps, and announce alarms.
12.5.5 Description of the Operation of the FOGs Reception Station
The FOG reception station is designed to be operated automatically, with little attention from the operator and the FOG
carrier. This station will accept FOG from the transporters, equalize and heat the FOGs, and transfer the FOGs from
the storage tanks to the anaerobic digesters automatically. The detailed functional description of the receiving station
of the FOGs is summarized below:
•
The transport system of the FOGs will be connected to the quick connection piping of the receiving station
and will discharge, through the rock trap and the crusher.
•
The FOG lift station will collect the FOGs and two recirculation crusher pumps will be transferred to the FOG
storage tanks by a level transmitter located at the lift station.
•
The storage tank / equalization heating and recirculation systems will operate continuously. These pumps will
be stopped automatically based on a low set point in the tank.
•
The FOG transfer pumps, from the storage tank / equalization tank to the digesters, will be variable speed.
The speed and flow rate of the pumps will initially be selected by the operator, based on the amount of grease
stored in the tank and the anticipated discharges of the next day. The pump speed will automatically increase
if the FOG level reaches a high level set point. The pump speed will increase even further if the FOG level
reaches a high-high set point. The speed of the pump will also increase to the maximum speed if the level of
the FOG reaches a point where the available storage volume is below 3,800 L (the capacity of the FOG
tankers).
•
The sludge / FOG piping will be designed to circulate the fluid between the digesters in service, with a
continuous pumping 24 hours a day, 7 days a week.
•
When a high pressure set point is reached in the transfer line, or a low water set point in the storage and
mixing tank, the transfer pumps will be stopped automatically. The pumps will shut down automatically if the
discharge pressure within the line reaches a certain set point, which may indicate an obstruction in the line,
or that all valves to the digesters are closed.
•
The pumps will be exchanged for equitable wear after each use or a set operating time interval. The lead
pump / secondary pump sequence can also be set manually.
SECTION 12
CALCULATION MEMORY – A
BALANCE OF MASS FOR SOLIDS
PTAR LAS ESCLUSAS
BALANCE OF MASS FOR SOLIDS
The calculation of the mass balance calculation for the solids of the PTAR Las Esclusas has been developed for the
following load conditions:
•
Dry Weather
•
Weather Wet
•
Average Annual Payload (CPA)
•
Monthly Maximum Load (CMM)
•
Maximum weekly load (CMS)
The mass balance for the solids produced under the conditions mentioned above is part of the estimation of primary
sludge production in the primary clarifiers. This estimation contemplates a calculation procedure for the determination
of the solids loads under the conditions of Dry Time and Wet Time, followed by a slightly different procedure for the
calculation under the conditions of CPA, CMM and CMS. Once the mud loads produced under these five conditions
were determined in the primary clarification process, the mass balance was carried out for the other sludge treatment
processes.
In another calculation report corresponding to the heating calculations of the digesters, the use of the methane gas
generated in the digesters when used as fuel in the cogeneration of electric energy will be analyzed for the heating of
the sludge present in the digesters. For simplicity in the analysis carried out in the heating calculation memory of the
digesters of the data recorded in the present mass balance of solids, only values corresponding to the CPA, CMM and
CMS conditions were used.
For the estimation of the loads in Dry Time and in Wet Time, the following input parameters were used:
Chart 1
Parameters of the Inflow to the PTAR Las Esclusas for Conditions of Dry Weather
and Wet Weather (Year 2,030)
Parameter
Dry weather
Wet weather
Flow (m3/s)
2.66
3.63
DBO5
156
126
130
105
(mg/L)
SST (mg/L)
Also, to estimate the production of solids in Dry Time and Wet Time, the recirculation flow rates of the plant
corresponding to the supernatant of the thickening by gravity and the filtration of the dehydration process were taken
into account. The calculation of recirculation flows can be found in the mass balance of the particular processes that
produce them. Also, to estimate the production of solids in Dry Time and Wet Time, the recirculation flow rates of the
plant corresponding to the supernatant of the thickening by gravity and the filtration of the dehydration process were
taken into account. The calculation of recirculation flows can be found in the mass balance of the particular processes
that produces them.
In accordance with the above, the estimation of the solids production for the primary clarification process under Dry
Weather and Wet Weather conditions is shown below.
Chart 2
Mass Balance for Primary Clarification Under Dry Weather and Wet Weather Conditions
Parameter
Dry weather
Wet weather
Flow (m3/s)
2.66
3.63
DBO, mg/L
156
126
SST, mg/L
130
105
35853
39518
35.9
39.5
29877
32931
29.9
32.9
Flow (m3/s)
0.012
0.013
DBO, mg/L
0.1
0.1
DBO load, kg/day
906
999
SST, %
0.1
0.1
1.077
1.113
Flow (m3/s)
0.01
0.01
DBO, %
0.1
0.1
DBO load, kg/day
512
548
SST, %
0.1
0.1
SST load, kg/day
618
613
Flow (m3/s)
2.68
3.65
DBO, mg/L
156
126
SST, mg/L
130
105
37271
41066
37.3
41.1
31572
34657
31.6
34.6
Influent flow
DBO load, kg/day
DBO load, TON/day
SST load, kg/day
STT load, TON/day
Recirculation flow
Gravity Thickening Supernatant
SST load, kg/day
Dehydration Filtration
Affluent to Primary Clarification
DBO load, kg/day
DBO load, TON/day
SST load, kg/day
STT load, TON/day
Primary Clarification Removals (with contribution of recirculation flows)
DBO remotion, %
42%
42%
SST remotion, %
62%
62%
Primary Clarification Effluent
DBO load, kg/day
21617
23818
DBO load, TON/day
21.6
23.8
DBO, mg/L
93.6
75.6
12012
13237
STT load, TON/day
12
13.2
SST, mg/L
52
42
18018
19856
80%
80%
14414
15885
3604
3971
40
20
SST load, kg/day
Raw Primary Sludge (LP)
Solid Load, kg ST/d
Fraction of Volatile Solids,
SV/ST
Volatile Solids Load, kg
SV/d
Load of NonVolatiles, kg SNV/d
Chemical Precipitation
Ferric Chloride Dosage, mg/L
Ferric Sludge Production (kg/m3 treated /
mg/L dosed)
0.000383
Production of Chemical Sludge, kg/d
3522
2403
Production of Chemical Sludge, TON/d
3.52
2.4
Solid Load, kg ST/d
21540
22259
Solid concentration, %ST
1.50%
1.50%
Fraction of Volatile Solids,
SV/ST
66.90%
71.40%
1.436
1484
14414
15885
7126
6374
Raw Primary Sludge + Chemical Sludge (LP + Q)
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of NonVolatiles, kg SNV/d
Note: As can be seen in the Table, the contribution of the recirculation flow rates (supernatant of thickening by gravity
and filtering of the band press filters) is very low, so that the associated loads were not taken into account in the sludge
Resulting from the process (raw primary sludge + chemical sludge).
On the other hand, for the calculation of the solids production in primary clarification under CPA, CMM and CMS
conditions, the following input parameters were assumed:
In accordance with the above, the estimation of solids production for the primary clarification process under the
conditions of CPA, CMM and CMS is shown below.
Chart N.4
Balance of Mass for Primary Clarification Under CPA, CMM and CMS Conditions
Parameter
Average Annual Load
(CPA)
Monthly Maximum Load
(CMM)
Weekly Maximum
Load (CMS)
Raw Primary Sludge (LP)
Solid Load, kg ST/d
19500
24375
29520
80%
80%
80%
Volatile Solids Load, kg SV/d
15600
19500
23400
Load of Non-Volatile Solids,
kg SNV/d
3900
4875
5850
2
3.7
7.4
40
30
20
3674
4899
Fraction of Volatile Solids,
SV/ST
Chemical Precipitation
Flow rate, m3/s
Ferric Chloride Dosage, mg /
L
Ferric Sludge Production
(kg/m3 treated / mg/L
dosed)
Production of Chemical
Sludge, kg/d
0.000383
2648
Raw Primary Sludge + Chemical Sludge (LP + Q)
Solid Load, kg ST/d
22148
28049
34149
Solid concentration, %ST
1.50%
1.50%
1.50%
Fraction of Volatile Solids,
SV/ST
70.40%
69.50%
68.50%
Flow (m3/day)
1477
1870
2277
Volatile Solids Load, kg
SV/d
15600
19500
23400
Load of Non- Volatiles, kg
SNV/d
6548
8549
10749
Solid Load, kg ST/d
2300
2300
2300
Solid concentration, %ST
Fraction of Volatile Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Fats and Oils Retained (G & A)
Solid Load, kg ST/d
40%
40%
40%
95%
95%
95%
5.75
5.75
5.75
2185
2185
2185
115
115
115
1050
1050
1050
3%
3%
3%
97%
97%
97%
35
35
35
1019
1019
1019
32
32
32
Concentrated Primary Foam (EP)
Solid concentration, %ST
Fraction of Volatile Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
As mentioned above, once the solids loads produced in the primary clarification were determined for each of the
conditions studied, the mass balance was performed for the subsequent processes. The assumed input parameters
for
below.
gravity
thickening are shown
In accordance with the above, the mass balance performed for the thickening by gravity is shown below.
Chart N. 6
Mass Balance for Gravity Thickness
Average
Monthly
Weekly
Parameter
Annual Load
Maximum
Maximum
(CPA)
Load (CMM)
Load (CMS)
Raw Primary Sludge + Chemical Sludge (LP + Q)
Dry
weather
Wet
weather
Solid Load, kg ST/d
22148
28049
34149
21540
22259
Solid concentration, %ST
1.5%
1.5%
1.5%
1.5%
1.5%
Fraction of Volatile Solids,
SV/ST
70.4%
69.5%
68.5%
66.9%
71.4%
1477
1870
2277
1436
1484
15600
19500
23400
14414
15885
6548
8549
10749
7126
6374
Solid Surface Load, kg ST / d
/ m2
83.4
105.7
128.6
81.1
83.8
Surface Hydraulic Load, m3
/ m2-d
5.6
7
8.6
5.4
5.6
Hydraulic Retention Time
(SSV-based), hrs
17.3
13.6
11.2
17.7
17.2
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Gravity Thickness Design Bases
Thickened Primary Sludge (TPS)
Solid Load, kg ST/d
21041
26647
32442
20463
21146
Solid concentration, %ST
4.5%
4.5%
4.5%
4.5%
4.5%
Fraction of Volatile Solids,
SV/ST
70.4%
69.5%
68.5%
66.9%
71.4%
468
592
721
455
470
14820
18525
22230
13693
15091
6221
8122
10212
6770
6055
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Gravity Thickening Supernatant
Solid Load, kg ST/d
1107.41
1402
1707
1077
1113
Solid concentration, %ST
0.1%
0.1%
0.1%
0.1%
0,11%
Fraction of Volatile Solids,
SV/ST
70.4%
69.5%
68.5%
66.9%
71.4%
1009
1278
1556
981
1014
780
975
1170
721
794
327
427
537
356
319
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
The assumed input parameters for the mass balance of anaerobic digestion are shown below.
Chart N. 7
Design Parameters for Anaerobic Digestion
Parameter
Number of digesters
Value
Volume of each digester, m3
5000
3
Diameter, m
27
Area, m2
573
Depth at Wall Level, m
8.7
For the anaerobic digestion, it is necessary to estimate the Destruction of Volatile Solids (SV) based on the Solid
Retention Time, for which curves were developed from data reported in the literature1. Using the equation of this curve,
the corresponding percentages of SV destruction were calculated according to each solid loading condition. The
exercise performed is shown below.
Chart N. 8
Reduction of Volatile Solids based on WEF MOP 8
% Destruction of Volatile Solids
TRS
(days)
100% Activated
Waste Sludge
100% Primary
Sludge
Calculated for
Primary Sludge
10
8
50
50
11.3
11
52
52
12.5
13
54
54
13.8
16
56
56
15
18
58
57
16.3
19
59
58
17.5
21
60
59
18.8
22
61
60
20
23
62
61
21.3
24
62
61
22.5
24
62
62
23.8
25
62
62
25
26
63
63
26.3
26
63
63
27.5
27
63
63
28.8
27
63
63
30
28
63
63
31.3
28
63
63
32.5
29
63
64
33.8
29
63
64
35
30
64
63
37.5
30
64
63
40
31
64
63
42.5
32
64
64
45
32
65
64
47.5
32
65
65
50
33
65
66
In accordance with the above, the mass balance performed for anaerobic digestión.
Chart N. 10
Mass Balance for Anaerobic Digestion
Monthly
Average Annual
Weekly Maximum
Parameter
Maximum Load
Load (CPA)
Load (CMS)
(CMM)
Thickened Primary Sludge (TPS)
Solid Load, kg ST/d
Solid concentration,
%ST
Fraction of Volatile
Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load,
kg
SV/d
Load of NonVolatiles, kg SNV/d
Dry
Wet
weather weather
21041
26647
32442
20463
21246
4.5%
4.5%
4.5%
4.5%
4.5%
70.4%
69.5%
68.5%
66.9%
71.4%
468
592
721
455
470
14820
18525
22230
13693
15091
6221
8122
10212
6770
6055
2300
2300
2300
2300
2300
40%
40%
40%
40%
40%
95%
95%
95%
95%
95%
5.75
5.75
5.75
5.75
5.75
2185
2185
2185
2185
2185
115
115
115
115
115
1050
1050
1050
1050
1050
3%
3%
3%
3%
3%
97%
97%
97%
97%
97%
35
35
35
35
35
Concentrated Primary Foam (EP)
Solid Load, kg ST/d
Solid concentration,
%ST
Fraction of Volatile
Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load,
kg
SV/d
Load of NonVolatiles, kg SNV/d
Fats and Oils Retained (G & A)
Solid Load, kg ST/d
Solid concentration,
%ST
Fraction of Volatile
Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load,
kg
SV/d
1018.5
1018.5
1018.5
1018.5
1018.5
Load of NonVolatiles, kg SNV/d
31.5
31.5
31.5
31.5
31.5
24391
29997
35792
23813
24496
4.8%
4.7%
4.7%
4.8%
4.8%
74%
72%
71%
71%
75%
508
633
762
495
511
18024
21729
25434
16897
18294
6367
8268
10358
6916
6202
Mixing Feeding to Digesters
Solid Load, kg ST/d
Solid concentration,
%ST
Fraction of Volatile
Solids,
SV/ST
Flow (m3/day)
Volatile Solids Load,
kg
SV/d
Load of NonVolatiles, kg SNV/d
Loading Digesters
Number of digesters
operating
Total volume of
digesters, m3
2
10000
Solid Retention Time
(SRT) in Digesters, d
19.7
15.8
13.1
20.2
19.6
Loading SV to
Digesters, kg SV/d /
1,000 m3
1802
2173
2543
1690
1829
Design for minimum 15 days of SRT under Max Monthly condition with a digester out of service
Number of digesters
operating
Total volume of
digesters, m3
Solid Retention Time
(SRT) in Digesters, d
3
15000
29.5
23.7
19.7
30.3
29.4
Loading SV to
Digesters, kg SV/d /
1202
1449
1,000 m3
Digestion Performance - With Digester Out of Service
1696
1126
1220
Destruction of Volatile
Solids from Primary
Sludge,%
63%
62%
61%
63%
63%
Destruction of Volatile
Solids from G & A and
EP,%
97%
97%
97%
97%
97%
Total Destruction of
Volatile Solids, kg Sv /
d
12090
13793
15294
11447
12246
Digesters Performance - All in Service
Destruction of Volatile
Solids from Primary
Sludge,%
63%
62%
61%
63%
63%
Destruction of Volatile
Solids from G & A and
EP,%
97%
97%
97%
97%
97%
Total Destruction of
Volatile Solids, kg Sv /
d
12507
14669
16584
11798
12678
Anaerobic Digested Sludge - With the Principal Digester Out of Service
Solid Load, kg ST/d
12301
16204
20498
12366
12250
Solid concentration,
%ST
2.4%
2.6%
2.7%
2.5%
2.4%
Fraction of Volatile
Solids,
SV/ST
48%
49%
49%
44%
49%
Flow (m3/day)
508
633
762
495
511
Volatile Solids Load,
kg
SV/d
5934
7936
10140
5450
6048
Load of NonVolatiles, kg SNV/d
6367
8268
10358
6916
6202
General Anaerobic Digestion Performance - With the Principal Digester Out of Service
General Volatile Solids
Reduction,%
69%
Gas Production by SV
Destroyed, m3 / kg SV
Removed
0.94
Production of Gas
from Digesters, m3/d
11364.48
68%
65%
70%
69%
12965
14376
10760
11511
The following table shows the design parameters for the digested solids storage tank.
The mass balance for the digested solids storage tank is shown below.
Note: Design for 4 days of storage under Max Monthly Conditions to allow Dehydration Systems maintenance during
weekends and holidays.
The last process contemplated in the mass balance for the solids corresponds to the dehydration with band press
filters. The design parameters are shown below.
To finalize the present document, the mass balance for the dehydration process is shown.
Chart N. 14
Parameter
Mass Balance for Dehydration
Monthly
Average Annual
Weekly Maximum
Maximum Load
Load (CPA)
Load (CMS)
(CMM)
Dry
weather
Wet
weather
Anaerobic Digested Sludge
Solid Load, kg ST/d
12301
16204
20498
12366
12250
Solid concentration, %ST
2.4%
2.6%
2.7%
2.5%
2.4%
Fraction of Volatile Solids,
SV/ST
48.2%
49.0%
49.5%
44.1%
49.4%
508
633
762
495
511
508323
632903
761677
495483
510665
5934
7936
10140
5450
6048
6367
8268
10358
6916
6202
16.9
26
25.3
Flow (m3/day)
Flow (L/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Daily Storage Tanks for Dehydration
Number of tanks
Tank width, m
Depth of the tank, m
2
7.33
5
Length of each tank, m
7.33
Volume for each tank, m3
269
537
Total volume, m3
25.4
20.4
Storage hours
Design for 24 hours storage under the condition Average Annual
Operational Requirements of Filters Band Press - 7 days a week
Hr/Day of Operation Limited by the Load of Solids
3.9
5.1
6.5
3.9
3.9
Hr/Day of Operation Limited by Hydraulic Load
4.1
5.1
6.1
4
4.1
Hr/Day of Operation Critical Value
4.1
5.1
6.5
4
4.1
Hydraulics
Solid
Solid
Hydraulics
Hydraulics
17%
21%
27%
17%
17%
5.5
5.4
5.6
5.8
Limiting Load
% Used of Available Capacity
(24 hr of Operation)
Operational Requirements of Filters Band Press - 5 days a week
Hr/Day of Operation Limited by the Load of Solids
5.5
7.2
9.1
Hr/Day of Operation Limited by Hydraulic Load
5.7
7.1
8.6
Hr/Day of Operation Critical Value
5.7
7.2
9.1
5.6
5.8
Hydraulics
Solid
Solid
Hydraulics
Hydraulics
24%
30%
38%
23%
24%
11686
15394
19473
11747.79
11637.79
Solid concentration, %ST
27%
27%
27%
27%
27%
Fraction of Volatile Solids,
SV/ST
48.2%
49%
49.5%
44.1%
49.4%
43
57
72
44
43
5637
7539
9633
5177
5746
6049
7855
9840
6570
5891.83
615
810
1025
618
613
Solid concentration, %ST
0.08%
0.090%
0.090%
0.09%
0.08%
Fraction of Volatile Solids,
SV/ST
48.2%
49.0%
49.5%
44.1%
49.4%
Flow rate of solids, m3/d
465
576
690
452
468
Spraying Water Flow, m3/d 7 days/no Operation
276
347
439
269
278
741
923
1129
721
745
297
397
507
272
302
318
413
518
346
310
Limiting Load
% Used of Available Capacity
(24 hr of Operation)
Dehydrated cake
Solid Load, kg ST/d
Flow (m3/day)
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Filtered out
Solid Load, kg ST/d
Total flow, m3/d
Volatile Solids Load, kg
SV/d
Load of Non- Volatiles, kg
SNV/d
Note:
The installation of 4 units is recommended in order to be able to handle the variability in the quantity of solids, and to
lower the cost of polymers.
The normal operation will comprise 3 available units and 1 reserve, working 5 days per week and 6 hours per day, to
allow both the start and the washing of the units within an 8-hour workshift.
SECTION 12
CALCULATION MEMORY – B
EQUIPMENT ASSOCIATED TO WASTE
MANAGEMENT - ANAEROBIC DIGESTION
•
Mixing Pump:
Equipment labeling: 701 – 706
Total capacity installed (kW): 57 each
Pump Capacity (gpm): 5,000
The sizing of the pumps and motors for the digester mixing system was provided by Vaughan, a
mixing system manufacturer. They used the digester tank size, configuration and percent solids content
of the sludge to determine the required pump/motor capacity for mixing. Two (2)
pump/motors will be provided for each digester. They will be configured one (1) Duty and one
(1) Standby.
•
Heating pump:
Equipment labeling: 707 – 711
Total capacity installed (kW): 7.5 each
Pump Capacity (gpm): 360
The sizing of the pumps and motors for digester heating is from manufacturer’s standard sizes of tube-intube heat exchangers that meet the heating demand of the digester. For the digester heating pumps this
flow rate was determined to be 360 GPM. From this system curve at a flow of 360 gpm (0.52 MGD) the
TDH for the pump is 32’. A Wemco 4x11 CE Torque Flow Pump was selected to meet the flow and head
conditions. This pumps would require a 10 HP motor (7.5 kW).
•
Rotary pump
Equipment labeling:712 – 714
Total capacity installed (kW): 15 each
Pump Capacity (gpm): 400
The sizing of the pumps and motors for digested sludge transfer are dependent on the feeding rate of the
digesters from the thickened sludge pumps. The thickened sludge pumps (4 duty pumps) are designed to
send a maximum total feed flow of 800 gpm to the digesters. If all four
(4) thickened sludge duty pumps and the two (2) standby pumps are running the “All” on flow is 1,200
gpm. There are three (3) digested sludge transfer pumps. They are designed in a two (2)
duty and one (1) standby arrangement. Each pump will be designed for a capacity of 400 gpm
each. The two (2) duty pumps be able to match the maximum digester feed flow and all three (3) pumps
will be able to match the all on flow from the thickened sludge pumps. A system curve was developed by
Hazen for the transfer of sludge from the digesters to the digested sludge holding tank. At the typical
digested sludge concentration of 2.5% total solids, determined the pumps would need to be able to handle
a TDH of 76’ when two (2) pumps were running at 400 gpm each and when three (3) pumps were running
at 400 gpm each. The system curve can be found in the file: 030 – Digested Sludge Transfer Pumps Design.
To account for variability of solids concentration and digester performance, the design point of 400 gpm
@ 115’ TDH parameters a Moyno progressive cavity pump was selected to allow pumping up to 4.5%
solids. A single stage 2000 series pump with a 20 HP (15kW) motor will be able to handle the conditions.
•
Crusher for Rotative Pump:
Equipment Labeling: 715 – 717
Total capacity installed (kW): 3.7 each
Capacity (gpm): 800
The inline grinders and motors are sized at a minimum to meet the transfer pump capacities and then
upsized to match the pipe suction size of 8”. The transfer pumps are designed for maximum flow of 400
gpm. The transfer grinders are also sized to match the suction line size of 8”. The 8” Muffin Monster
grinder can handle a flow of 800 gpm. There is a dedicated grinder to each transfer pump. The motor
sizing for the grinders will be 5 HP (3.7 kW).
•
Primary hot water pump:
Equipment labeling: 718 – 719
Total capacity installed (kW): 5.6 each
Pump Capacity (gpm): 600
The sizing of the primary hot water loop pumps is dependent on the heating requirements of the digesters,
fine screen spray wash, FOGs tank and FOGs washdown water. The maximum hot
water flow required to provide heat transfer to all facilities was determined to be 600 gpm (see
Excel file: Hot Water Heat Balance). There will be one (1) duty and one (1) standby hot water pump. A
system curve was developed by Hazen to determine the headloss in the primary hot water loop at
maximum flow (see File : 051 – Primary Hot Water Loop Pump Design). The TDH @ 600 gpm for the system
was 32’. A Bell and Gossett series 1510 pump with a 7.5 HP (5.6 kW) will meet the requirements.
•
Secondary hot water pump:
Equipment labeling: 720 – 723
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 200
The sizing of the pumps and motors for the secondary loop hot water pumps is dependent on digester
heat exchanger design. (filename: Las Esclusas Digester Heating Calculations – tab Maintenance Heating).
For the secondary loop pumps this flow rate was determined to be 200 GPM. Hazen then created a
secondary heating loop system curve (filename: 060 – Secondary Hot Water Loop Pumps Design). The
TDH @ 200 gpm for the system was 40’. A Bell and Gossett series 80 standard inline pump with a 5.0 HP
(3.7 kW) motor will meet the requirements, Secondary Hot Water Loop Pump Selection. There will be four
(4) pumps of this capacity provided. There will be one (1) pump installed and dedicated to each digester
heat exchanger for a total of three (3). The fourth pump will be an uninstalled spare.
•
Hot water pump FOG:
Equipment labeling: 724
Total capacity installed (kW): 0.75 each
Pump Capacity (gpm): 80
File 070 – FOG System Design Calculations outlines the heating requirements for the FOGS storage tank.
A Walker HEX (see file 071 – FOG HEX) was selected. From the HEX it was determined 80 gpm of hot water
was required. Hazen created a system design for the secondary hot water loop and determined a pump
capable of 80 gpm @ 22’ TDH was required, see file 072 – FOG HEX Hot Water Pump Design. A Bell and
Gossett pump was selected with a 1 HP motor.
•
Washdown hot water pump:
Equipment labeling: 726
Total capacity installed (kW): 0.38 each
Pump Capacity (gpm): 20
Both the digester and FOGS facilities will benefit from hot washdown/flushing water when needing to
clean piping, thanks etc. The FOGs facility will benefit most. A plate and frame heat exchanger will be
utilized to heat the plant washdown water using the primary hot water loop. The secondary inline pump
that will push hot water through this heat exchanger is called the FOGs Washdown Hot Water Pump. The
design for this pump can be found in file 081 – FOG Washdown Hot Water Pump Design. This pump is
designed to flow 20 gpm @ 12’TDH utilizing a ½ HPpump.
•
Boiler:
Equipment labeling: 727
Total capacity installed (kW): 1.5 each
Capacity (BTU/hr): 2,678,000
The boiler was designed for a rated output of 2,678,000 BTU/hr (80 Boiler HP). This boiler will require a 2
HP (1.5 kW) motor blower motor based on the Clever Brooks Model of this size.
•
Boiler - pump:
Equipment labeling: 728 – 729
Total capacity installed (kW): 1.1 each
Pump Capacity (gpm): 100
There will be two (2) boiler feed pumps. They will be one (1) duty and one (1) standby. Each pump is sized
based on the maximum circulation rate for an 80 HP boiler from Clever Brooks. A system design for the
boiler feed pumps was created by Hazen, see file 100 – Boiler Feed Pump Design. The pump is designed
for 100 gpm @ 27’ TDH. The Bell and Gossett Model 2.5 AB pump with a 1.5 HP (1.1 kW) motor was
selected to fit the demands.
•
FOG discharge pump:
Equipment labeling: 730 – 731
Total capacity installed (kW): 15 each
Pump Capacity (gpm): 100
There will be two (2) FOGs unloading pumps located at the FOGs receiving facility to pump FOG from the
receiving facility wetwell to the FOG storage tank. They will be configured one (1) duty and one (1)
standby. File FOG System Design Calculations determined each pump is required to be able to pump 1,000
gpm, which is a typical maximum off-loading rate from a grease trap vacuum truck. A system design for
the unloading pumps was developed by Hazen and can be found in file 110 – FOGs Unloading Pump
Design. The system design determined the 1,000 gpm pumps need to be able to handle approximately 50’
TDH. A Vaughan E series Vertical Chopper Pump was picked for this application. A 25 HP (18.8 kW) motor
will be used for each pump. File 111 – FOGs Unloading Pumps is the manufacturers pump curve.
•
Mixing pump of FOG:
Equipment labeling: 732 – 733
Total capacity installed (kW): 15 each
Pump Capacity (gpm): 1,000
The sizing of the pumps and motors for the FOG mixing system was provided by Vaughan, a mixing system
manufacturer. They used the FOG tank size, configuration and percent solids content of the FOG to
determine the required pump/motor capacity for mixing. Two (2) pump/motors will be provided. They
will be configured one (1) Duty and one (1) Standby.
•
Heating pump of FOG:
Equipment labeling: 734
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 150
The sizing of the pump and motor for FOG heating is from manufacturer’s standard sizes of tube-in-tube
heat exchangers that meet the heating demand of the FOG storage tank. (filename: FOG System Design
Calculations). For a 74 kW heat exchanger requires a FOG flow of 150 GPM. Hazen then created a heating
loop system curve (filename: 140 – FOGs Heating Pump Design). From this system curve at a flow of 150
gpm (0.22 MGD) the TDH for the pump is 19’. The pump was designed for 150 gpm @ 37’ to account for
clogging. A Moyno progressive cavity pump was selected. The Moyno pump will require a 5.0 HP (3.7 kW)
motor.
•
FOG transfer pump:
Equipment labeling: 736 – 737
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 30
The FOGs feed pumps will transfer stored FOGs from the FOGs storage tanks to the digesters. The pumps
are designed to constantly feed FOGs rotating through the digesters in service to evenly distribute the
flow. Calculations performed in file FOG System Design Calculations indicate a maximum average rate of
FOG received of 12.8 gpm (2.9 m3/hr). To accommodate for unbalanced FOG delivery throughout the day
the FOG feed pumps will be designed for 30 gpm (7 m3/hr). The system design indicates a TDH of 49’ at
30 GPM. The pump to be used for this application was selected to operate at 30 gpm @ 138’ to account
for clogging. A Moyno 2000 series progressive cavity pump was selected for this application. This pump
will require a 5 HP (3.7 kW) motor.
•
FOG grinder:
Equipment labeling: 738
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 400
This grinder is located at the FOGs receiving station and will process FOGs as it is unloaded from the trucks
after it passes through the rock trap and before it enters the unloading pump wet well. It is anticipated
the truck will be able to unload at 635 gpm (40 L/s). To accommodate max flows with minimum headloss
through the grinder an 8” grinder with a 5 HP (3.7 kW) motor was selected.
•
FOG Crusher Heating:
Equipment labeling: 739
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 150
This grinder is located upstream of the FOGs heating pumps and will process the same flow as the heating
pump capacity. The grinder will require a 5 HP (3.7 kW) motor was selected.
•
FOG Crusher Transfer:
Equipment labeling: 740 - 741
Total capacity installed (kW): 3.7 each
Pump Capacity (gpm): 30
These grinders are located upstream of the FOGs transfer pumps and will process the same flow as the
transfer pump capacity. The grinder will require a 5 HP (3.7 kW) motor.
•
Fine Screens Spray Hot Water Pump
Equipment labeling: 742
Total capacity installed (kW): 1.2 each
Pump Capacity (gpm): 80
The Fine Screens will need heated spray water. The primary hot water loop will be used to heat the spray
water by utilizing a plate and frame heat exchanger. The design flows for the hot water through the heat
exchanger will be 80 gpm. The system was modeled and it was determined the pumps would need to be
able to handle a TDH of 28’. A Bell and Gossett series 1510 Model 2x2x5.25 pump with a 1.5 HP (1.2 kW)
motor was selected.
•
Air blowers for gasometers:
Equipment labeling: 801 - 802
Total capacity installed (kW): 1.5 each
Capacity (cfm): N.A.
The double membrane digested gas holder will need to have the outer membrane inflated by a blower.
The blower will be supplied by the membrane manufacturer. There will be two (2) blowers provided, one
(1) duty and one (1) standby. The size of the blowers has been estimated based on information from
manufacturer of Gasholder.
•
Multi-Stage Centrifugal Blowers for Biogas:
Equipment labeling: 803 – 804
Total capacity installed (kW): 30 each
Capacity (cfm): 600
The Maximum flow of digester gas that would be needed by 3 engine generators and 1 boiler would be
592 cfm (1,005 m3/hr) as shown in file Las Esclusas Digester Heating Calculations. Each blower (which is
part of the digester gas cleaning and drying system) will be capable of processing this flow. From a blower
curve specific to digester gas, the design point of 600 CFM at 7.5 psi results in 35 BHP, see file 160 – Gas
drying Blowers. The blowers will be sized for 40 HP (30 kW) to handle the proposed loading.
•
Biogas cooler:
Equipment labeling: 805
Total capacity installed (kW): 45 each
Capacity (BTU/Hr): 150,000
The glycol chiller for the digester gas compressor/dryer will be supplied by the manufacturer. Using
estimates from previous projects similar in size and scope the chiller would draw approximately 60 amps.
At 3 phase 460 V power the chiller would use approximately 60 HP (45
kW) of power.
•
Fan for cooling of biogas:
Equipment labeling: 806
Total capacity installed (kW): 0.8 each
Capacity (gpm): N.A.
This fan cools the biogas before entering the heat exchanger as part of the digester gas cooling
and drying. It is estimated to be 1 hp (0.8 kW) based on previous projects of similar scope and
size.
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