The SHAFDAN is the largest wastewater treatment plant in Israel and currently treats 360,000 m3/day of municipal wastewater, about 92% of its treatment capacity. Waste sludge from the plant is discharged to the Mediterranean Sea through a marine outfall. The SHAFDAN is committed to ending the disposal of its sludge to the sea by the end of 2016 by providing a land-based biosolids management program that produces a Class A biosolids for agricultural use. In order to implement this strategy, a number of large-scale construction projects were undertaken. These projects include a new sludge thickening and dewatering facility, updated headworks, a new primary treatment facility, and a new 3-stage thermophilic anaerobic digestion facility. The total capital cost of these projects is estimated to be US $300 million. This paper describes the principal components of these projects and their design parameters. INTRODUCTION The SHAFDAN (Greater Tel Aviv Wastewater Treatment Plant) is the largest regional wastewater treatment plant in Israel. The plant treats wastewater from 35 municipalities. The population served by the SHAFDAN is approximately 2.3 million people. In 2014, the plant treated an average daily flow of about 360,000 m³/d. The raw wastewater has a relatively high strength: BOD = 400 mg/l; TSS = 410 mg/l; TKN = 70 mg/l; P = 10 mg/l (Mey Ezor Dan 2014). The SHAFDAN was originally constructed in the 1960s as a large earth-lagoon oxidation pond system followed by lime-treatment and ammonia–stripping lagoons. The lagoon system was replaced by an extended aeration activated sludge facility, consisting of headworks, BNR bioreactors and final clarifiers. Primary clarifiers were not included in the facility. The secondary effluent meets very high quality standards with average values of BOD <6 mg/l; TSS <6 mg/l; TKN <6 mg/l; TP <1 mg/l. The effluent is infiltrated into a sand aquifer with an average retention time of 1 year, pumped and reused for unrestricted agricultural land application in the south of the country, supplying more than 70% of the irrigation needs. All the waste activated sludge (WAS) from the plant was discharged through a marine outfall. The current treatment process flow diagram is presented in Figure 1. Figure 1 SHAFDAN current process flow diagram. Figure 1 SHAFDAN current process flow diagram. As the plant is approaching its design capacity (the plant is currently at about 92% of its treatment capacity), SHAFDAN had chosen to add a primary treatment stage to reduce the organic loading to the secondary treatment process as part of the plant expansion. In accordance with a decision taken several years ago, SHAFDAN is also committed to developing a land-based biosolids management program, producing a Class A biosolids product for agricultural use by the end of 2016. In order to implement this strategy, the following facilities were designed and constructed: • Project I: thickening and dewatering facility (US$30,000,000)

• Project II: new headworks facility and new primary treatment facility to replace the old inefficient facilities (US $70,000,000) • Project III: three-stage thermophilic anaerobic digestion facility (US$200,000,000)

These 3 projects are among the world's largest of their kind. Project I have been completed and have been in operation for 3 years. Project II is now in the commissioning phase. Project III will be commissioned in early 2016.

Table 1 summarizes the major design parameters for the three projects mentioned above.

Table 1

SHAFDAN upgrade and expansion: major design parameters

Parameter Unit Value
Design Year year 2030
Average Annual Flow m3/d 500,000
Peak Hour Flow m3/sec 12
Primary Sludge – max. month m3/d 2,500
Primary Sludge – max. month t/d 110
WAS – max. month m3/d 24,300
WAS – max. month t/d 170
Parameter Unit Value
Design Year year 2030
Average Annual Flow m3/d 500,000
Peak Hour Flow m3/sec 12
Primary Sludge – max. month m3/d 2,500
Primary Sludge – max. month t/d 110
WAS – max. month m3/d 24,300
WAS – max. month t/d 170

Project I: thickening and dewatering facility

As the first stage in the implementation to discontinue the discharge of sludge to the sea, a thickening and dewatering facility was constructed and has been in operation for several years.

Three activities take place in the thickening and dewatering facility (Figure 2)
Figure 2

SHAFDAN thickening and dewatering building.

Figure 2

SHAFDAN thickening and dewatering building.

WAS thickening

The WAS taken from the final clarifier underflow is thickened from about 0.7% solids to about 5% solids on 11 gravity belt thickeners (GBTs) (Figure 3). Each GBT is served by a progressive cavity (PC) feed pump, and a second PC pump that pumps the TWAS to the digesters. The WAS thickening design parameters are presented in Table 2.
Figure 3

GBTs.

Figure 3

GBTs.

Table 2

WAS thickening: major design parameters (max. month)

Parameter Unit Value
Solids feed rate t/d 170
WAS solids concentration 0.7
WAS feed rate m3/d 24,300
Thickened WAS solids concentration
Thickened WAS flow m3/d 3,400
Thickener type and make GBT EMO; 3.5-m belt width
Installed machines No. 11 (including standby)
Parameter Unit Value
Solids feed rate t/d 170
WAS solids concentration 0.7
WAS feed rate m3/d 24,300
Thickened WAS solids concentration
Thickened WAS flow m3/d 3,400
Thickener type and make GBT EMO; 3.5-m belt width
Installed machines No. 11 (including standby)

Digested sludge dewatering

The combined primary and TWAS digested sludge is pumped to a pre-dewatering holding tank, and from there fed by dedicated PC pumps to 6 decanter centrifuges (Figures 4 and 5).
Figure 4

Centrifuge.

Figure 4

Centrifuge.

Figure 5

Dewatered sludge pumps.

Figure 5

Dewatered sludge pumps.

The sludge dewatering design parameters are presented in Table 3.

Table 3

Digested sludge dewatering: major design parameters (max. month)

Parameter Unit Value
Solid feed rate – Conc. t/d–% 170–2.9
Digested sludge feed rate m3/d 5,900
Solid concentration in dewatered sludge cake 20–25
Dewatered sludge cake mass t/d 850–680
Centrifuges type and make Decanter Alfa Laval Aldec G2–120
Installed machines No. 6 (including standby)
Parameter Unit Value
Solid feed rate – Conc. t/d–% 170–2.9
Digested sludge feed rate m3/d 5,900
Solid concentration in dewatered sludge cake 20–25
Dewatered sludge cake mass t/d 850–680
Centrifuges type and make Decanter Alfa Laval Aldec G2–120
Installed machines No. 6 (including standby)

Dewatered sludge cake pumping

The dewatered sludge cake, at 20 to 25% solids concentration, is pumped by special high-pressure PC pumps (one pump per decanter) to a nearby truck loading facility through 300 mm diameter, 120 m long discharge pipes (one pipe per pump). The maximum discharge pressure in the system is 36 bars. In the event that excessive pressure is developed and detected, lubrication pumps automatically reduce the pressure to normal values. The dewatered sludge pumping design parameters are presented in Table 4.

Table 4

Dewatered sludge pumps: major design parameters (max. month)

Parameter Unit Value
Dewatered sludge feed rate (per pump) m3/hr. 10 to 15
Dewatered sludge solids concentration 20 to 25
Type and make PC Seepex THE 70-48
Installed machines No.
Parameter Unit Value
Dewatered sludge feed rate (per pump) m3/hr. 10 to 15
Dewatered sludge solids concentration 20 to 25
Type and make PC Seepex THE 70-48
Installed machines No.

Project II: new headworks and primary clarifiers

A new headworks facility (Figure 6) was built to replace the old inefficient facility. A new primary treatment stage was added to reduce the organic loading to the secondary treatment process. The regular operation of the two facilities will start in 2015.
Figure 6

SHAFDAN new headworks and primary clarifiers.

Figure 6

SHAFDAN new headworks and primary clarifiers.

Diversion chamber and new sewer aqueduct

A diversion chamber and new influent sewer were constructed to convey the incoming wastewater to the new headworks facility (Figure 7).
Figure 7

Sewer aqueduct.

Figure 7

Sewer aqueduct.

The influent sewer consists of 2 pipes, each of 2.7 m internal diameter, pre-fabricated in segments, and based on special pile foundations.

The headworks treats the wastewater in 4 stages: very coarse screens, coarse screens, fine screens and grit removal (Figure 8).
Figure 8

Figure 8

The headworks design parameters are presented in Table 5.

Table 5

Parameter Unit Value
Design Peak Hour Flow m3/sec 12
Very coarse screens
Installed units No.
Design flow through each m3/sec
Channel width 3.2
Screen opening mm 100
Screenings conveyance  Belt conveyor
Type and make rake screen Huber Rake Max
Coarse screens
Installed units No.
Design flow through each m3/sec
Channel width 3.2
Screen opening Mm 20
Screenings conveyance  Screw conveyor
Type and make rake screen Huber Rake Max
Fine screens
Installed units No.
Design flow through each m3/sec 2.4
Channel width 2.4
Screen opening mm 6 (perforated plate)
Screenings conveyance  Water trough, chopping, pumping
Type and make Perforated Huber EscaMax
Grit traps
Installed units No.
Design flow through each m3/sec 2.7
Chamber diameter
Grit conveyance  Slurry pumping
Type and make vortex Jones & Atwood
Parameter Unit Value
Design Peak Hour Flow m3/sec 12
Very coarse screens
Installed units No.
Design flow through each m3/sec
Channel width 3.2
Screen opening mm 100
Screenings conveyance  Belt conveyor
Type and make rake screen Huber Rake Max
Coarse screens
Installed units No.
Design flow through each m3/sec
Channel width 3.2
Screen opening Mm 20
Screenings conveyance  Screw conveyor
Type and make rake screen Huber Rake Max
Fine screens
Installed units No.
Design flow through each m3/sec 2.4
Channel width 2.4
Screen opening mm 6 (perforated plate)
Screenings conveyance  Water trough, chopping, pumping
Type and make Perforated Huber EscaMax
Grit traps
Installed units No.
Design flow through each m3/sec 2.7
Chamber diameter
Grit conveyance  Slurry pumping
Type and make vortex Jones & Atwood

Primary clarifiers

A total of 20 rectangular primary clarifiers equipped with longitudinal chain and flight collectors were constructed Figure 9. The screened wastewater is fed through distribution channels. The sludge withdrawal from the hoppers is controlled by electrically actuated plug valves. The primary sludge is pumped by PC pumps along a central pipe gallery, to the anaerobic digesters. The primary clarifiers design parameters are presented in Table 6.
Figure 9

Primary clarifiers – upper and lower (pipe gallery) view.

Figure 9

Primary clarifiers – upper and lower (pipe gallery) view.

Table 6

Primary clarifiers: major design parameters

Parameter Unit Value
Design peak hour flow m3/sec 12
Number of clarifiers No. 20 (19 + 1 standby)
Clarifier tankage description
Length 45
Width 12
SWD 3.5 to 4
Floor slope
Area – per clarifier m2 540
Total area m2 10,800
Sludge hoppers per tank No.
Collector type and make Chain and flights Finnchain
Design parameters
Average overflow rate m3/m2/day 46
Max. overflow rate m3/m2/hr. 4.0
Performance – max. month
TSS removal efficiency 52 to 55
BOD removal efficiency 35
Primary sludge-dry matter kg/day 110,000
Primary sludge-flow m3/day 2,500
Sludge pumping
No. of units – total No. 20
Type and capacity  PC, 14 l/sec, VFD
Scum removal
Scum collection system  Elec. operated slotted pipe. Scum screening-compactor
Scum compaction
Parameter Unit Value
Design peak hour flow m3/sec 12
Number of clarifiers No. 20 (19 + 1 standby)
Clarifier tankage description
Length 45
Width 12
SWD 3.5 to 4
Floor slope
Area – per clarifier m2 540
Total area m2 10,800
Sludge hoppers per tank No.
Collector type and make Chain and flights Finnchain
Design parameters
Average overflow rate m3/m2/day 46
Max. overflow rate m3/m2/hr. 4.0
Performance – max. month
TSS removal efficiency 52 to 55
BOD removal efficiency 35
Primary sludge-dry matter kg/day 110,000
Primary sludge-flow m3/day 2,500
Sludge pumping
No. of units – total No. 20
Type and capacity  PC, 14 l/sec, VFD
Scum removal
Scum collection system  Elec. operated slotted pipe. Scum screening-compactor
Scum compaction

Project III: thermophilic anaerobic digestion facility

The sludge stabilization process selected by the SHAFDAN for a land-based biosolids management program producing Class A biosolids is based on a 3-stage thermophilic anaerobic digestion process. The start-up of the facility will begin in early 2016 Figures 10 and 11.
Figure 10

SHAFDAN anaerobic digester facility.

Figure 10

SHAFDAN anaerobic digester facility.

Figure 11

Anaerobic Digestion Facility Process Flow Diagram.

Figure 11

Anaerobic Digestion Facility Process Flow Diagram.

The digesters facility consists of:

• 8 sludge screens; 6 various sludge tanks

• 8 pumped-mixed thermophilic digesters

• Heat-exchangers and cooling systems

• Gas treatment facilities; 5 waste gas burners

• Membrane holding tank

• 8 co-generation unit

The anaerobic digester design parameters are presented in Table 7.

Table 7

Anaerobic digesters: major design parameters (max. month)

Parameter Unit Value
Blended sludge
Flow m3/d 5,900
Solids concentration 4.7
Sludge screening
Number No.
Max. flow per unit m3/hr. 68
Screening opening mm
Thermophilic digesters
Number (Stage 1/2/3) No. 6/1/1
Volume (each) m3 13,200
Volume (total) m3 105,800
Inner diameter 34
SWD 14.4
Operating temp. 57
HRT days 18
Mixing system  Pumped mixing
Mixing pumps number No. 24 (16 + 8 standby)
VSS reduction ≥ 50%
Biogas production m3/day 114,000
Biogas storage and treatment
Gas storage type  Dual membrane
Storage effective volume m3 4,300
Treat. for H2S removal  Biological (H2S ≤ 50 ppm)
Burners, number–capacity No.–m3/hr. 5–6,300
Burner type  Enclosed stack
Co-generation
Number of units No. 8 (7 operating, 1 in service)
Electrical output–each kW 1,400
Electrical output–total kW 9,800
Thermal output–each kW 1,400
Thermal output–total kW 9,800
Package  Containerized
Type and Make CHP Jenbacher JMC420
Siloxane removal  Activated carbon
Parameter Unit Value
Blended sludge
Flow m3/d 5,900
Solids concentration 4.7
Sludge screening
Number No.
Max. flow per unit m3/hr. 68
Screening opening mm
Thermophilic digesters
Number (Stage 1/2/3) No. 6/1/1
Volume (each) m3 13,200
Volume (total) m3 105,800
Inner diameter 34
SWD 14.4
Operating temp. 57
HRT days 18
Mixing system  Pumped mixing
Mixing pumps number No. 24 (16 + 8 standby)
VSS reduction ≥ 50%
Biogas production m3/day 114,000
Biogas storage and treatment
Gas storage type  Dual membrane
Storage effective volume m3 4,300
Treat. for H2S removal  Biological (H2S ≤ 50 ppm)
Burners, number–capacity No.–m3/hr. 5–6,300
Burner type  Enclosed stack
Co-generation
Number of units No. 8 (7 operating, 1 in service)
Electrical output–each kW 1,400
Electrical output–total kW 9,800
Thermal output–each kW 1,400
Thermal output–total kW 9,800
Package  Containerized
Type and Make CHP Jenbacher JMC420
Siloxane removal  Activated carbon

CONCLUSIONS

The SHAFDAN has been upgraded during the last 8 years to provide a biosolids management program producing Class A biosolids. Three major projects are involved in this plan: Project I – new sludge thickening and dewatering facility; Project II – new headworks facility and new primary clarifiers which provide a necessary treatment stage for a future expansion of the plant treatment capacity; Project III – a 3-stage thermophilic digestion facility. The total construction cost of these projects is approximately 300 million US dollars. These projects will provide the SHAFDAN with a state-of-the-art, long-term, land-based biosolids management system producing Class A biosolids.

As the plant is approaching its design capacity, the SHAFDAN is now preparing for the expansion of the liquid stream capacity to 500,000 m3/day. This expansion, planned for the next 10 years, involves a construction of new BNR bioreactors and final clarifiers as well as side-stream treatment of the dewatering centrate to reduce the nutrient return load to the secondary treatment process.

REFERENCES

REFERENCES
Mey Ezor Dan
2014
Dan Region Wastewater Project, Wastewater Treatment Plant Operation
.