Get documents about "Effluent Treatment Systems Material Selection Considerations
Document Sample
Effluent Treatment Systems
Material Selection
Considerations
Gordon Handziuk, PE
Gregory Vu, PE
October 10, 2007
Design Considerations for
Safe System Operation
1
Effluent Treatment Systems – Design Considerations
Trends & Requirements
• Guideline requirements:
• BMBL – BSL4 heat treatment is preferred.
• WHO – BSL4 heat treatment is preferred.
• DEFRA – Validated method.
• Canadian Guideline – CL4 heat treatment or chemical on
small scale throughput.
• Australian Guideline – PC4 heat or chemical treatment
Effluent Treatment Systems – Design Considerations
Fundamental Systems
Trend Towards Secondary Heat Treatment.
System Types:
• Batch Heat Treatment
• Continuous Heat Treatment
Chemical Treatment
•C
2
Effluent Treatment Systems – Design Considerations
Batch vs. Continuous Considerations
• Batch Heat Treatment Systems:
• Large throughput volumes.
• Animal space generates solids or
fines.
• Continuous Flow Heat Treatment
Systems:
• Bench labs – diagnostics.
• Animals in isolators.
• Limited amounts of solids.
Effluent Treatment Systems – Design Considerations
Key Considerations – Effects on Materials
• Thermal:
• Heat release – planned or unplanned, typically three
t ti l
potential sources.
• Autoclaves
• Heat treatment system
• Decontamination methodology.
• Chemical – lab use / decontamination methodology:
• Chlorine
• Quaternary Ammonia.
3
Pipe, Tank & Filter Material
Selection
Effluent Treatment Systems – Material Selection
Material Selection Criteria - General
• Thermal – Metal
• Carbon Steel / Alloys: Choice material
• Plastics: Will cause deformation
• Chemical – Plastics
• Plastics: Most demonstrate ‘good’ resistance
• Carbon Steel / Alloys: Effects of chlorine corrosion
increase with temperature
• Thermal & Chemical – Alloys
• Alloys: Varying grades of stainless steels demonstrate
resistance, selection is a cost factor
4
Effluent Treatment Systems – Material Selection
Thermal Considerations
• Autoclaves & Bulk Sterilizers:
• Typically discharged to a ‘closed’
ffl t t t t distribution,
effluent treatment di t ib ti
• Temperature and vapor discharge
release rate requires control,
• Decontamination Procedure:
• Steam – 250 F
• Non Thermal Alternatives:
Chemical (liquid) or vapor (Para-
formaldehyde, VHP).
Effluent Treatment Systems – Material Selection
Chemical Considerations
• Chlorine
steel,
• Corrosive to carbon steel
• Stainless Steels – Corrosion rate is dependent on
concentration and temperature of fluid.
• Compatible with a range of other plastics.
• ‘Server’ corrosion to PP – Polypropylene.
• Quaternary Ammonia
• Possible embrittlement towards PVC/CPVC, polypropylene
and PE
5
Effluent Treatment Systems – Material Selection
Chemical / Material Compatibility
‘Plastics’ ‘Alloys’
PP – Polypropylene
PE – Polyethylene
C22 – Hastelloy
CPVC
PTFE
304L
316L
904L
2205
PVC
Chlorine
Quaternary Ammonia
Temperature 140 210 210 160 280
Effluent Treatment Systems – Material Selection
Key System Components
• Filtration System
• Pipe & Tank Lining
6
Effluent Treatment Systems – Material Selection
Filtration System
• Bio-vents Filtration – Waste Venting
System:
• Material – Typically PTFE
• Temperature Range – 250 to 290F
• Pressure Differentials – 15 to 3 psi
• Waste venting system allows ‘free flow’
of air across the drainage system.
• Sterilizer equipment may be ‘hard
connected’ to plumbing system.
• ‘Planned’ discharge rate and
temperature requires control.
Effluent Treatment Systems – Material Selection
Critical Design Consideration
Bio-vents Filtration:
• Media Selection:
• Typically PTFE
• Coordination of filter capacity with
system demands:
• Autoclave Vacuum Pumps flow rate.
• Autoclave c a be d sc a ge flow
utoc a e chamber discharge o
rate.
• Heat treatment system release rate at
warm up.
7
Effluent Treatment Systems – Material Selection
Filtration System
• High Temperature / Pressure Filtration
– Safety Relief System:
• Material – Typically SS / Alloy
• Temperature Range – Up to 750F
• Pressure Differentials – Up to 150 psi
• SS / Alloy material better able to handle
high temperature / high flow rate of
‘unplanned’ di h
‘ l ff f t li f
d’ discharge off safety relief.
Effluent Treatment Systems – Material Selection
Critical Design Consideration
High Temperature / Pressure Filtration:
• Filter Media Selection:
• Typically Stainless Steel
• Coordination of filter capacity
with system:
• Discharge rate off safety
li f t heat treatment
reliefs at h t t t t
tanks and autoclaves.
8
Effluent Treatment Systems – Material Selection
Tank & Pipe Material – Selection
How to improve the life expectancy of the tank lining and pipe
in the presence of chlorine.
Material Selection Considerations:
• Reduce levels carbon content – 316L, 904L,…
• Introduction and/or increased levels Ni, Mo & Cr, this will
increase the overall material cost.
Effluent Treatment Systems – Material Selection
Tank & Pipe Material – Treatment
The heat treatment tank will be subjected to greatest level of
corrosion due to elevated temperatures. Two key
considerations:
1. Chlorine induced stress corrosion cracking (SCC).
More predominate at elevated temperatures.
• Occurs at welds and stresses in material.
• Critical temperature for SCC occurs at
F tanks.
122 F, primarily heat treatment tanks
• Action: Reduce working stresses
during fabrication to reduce overall
material stresses and reduce
the effects of SCC.
9
Effluent Treatment Systems – Material Selection
Alloy Considerations
• 316L can develop SCC with chlorine content at levels of
just a few ppm at 250F.
• C-22 Hastelloy can develop SCC with chlorine content at
levels of 24,000 ppm at 300F
Effluent Treatment Systems – Material Selection
Tank & Pipe Material – Treatment
The heat treatment tank will be subjected to greatest level of
corrosion due to elevated temperatures. Two key
considerations:
2. Crevice corrosion.
Action: Grind welds and
Electropolish tank surface
to eliminates crevices.
Additional: Passivate tank & pipe
to provide a protective oxide layer.
10
Comparative View of
Treatment Systems
Effluent Treatment Systems – Design Considerations
BSL 4 Batch Heat Treatment
• Lab Barrier Body Showers
• Chemical Showers
Entry /Exit
• Sinks
• Floor Drains &
BSL 4 BSL 4
Autoclaves Chem Showers
Entry/Exit
• Throughput 3500
gal/day Necropsy Necropsy
Airlock Airlock
• System Layout: Common Corridor
• Batch heat treatment Animal Animal Animal Animal
Holding Holding Holding Holding
• 316L + 904L Autoclave
11
Effluent Treatment Systems – Design Considerations
BSL 4 Batch Heat Treatment
• In this case, an AHJ Body Showers
requirement Entry /Exit
• Rupture discs
with Safeties BSL 4 BSL 4
High Temperature /
High Pressure
Relief Filter Skid Chem Showers
Entry/Exit
Necropsy Necropsy
Airlock Airlock
Common Corridor
Animal Animal Animal Animal
Holding Holding Holding Holding
Autoclave
Effluent Treatment Systems – Design Considerations
BSL4 – General Considerations
• Solids control:
• Strainer baskets at floor drains,
,
• Thermal / filtration control:
• Alloy based piping system.
• Vent filtration media selected for projected pressure &
temperature.
Plumbing fil i F ll d ffl l bi
• Pl bi filtration: Fully vented effluent plumbing system.
• High temperature / pressure filtration: Safety relief
discharge system independent from effluent discharge
system.
12
Effluent Treatment Systems – Design Considerations
BSL4 – General Considerations
• Chemical control:
• Tank: 316L, factory assembled.
• Pipe: 316L with 904L at traps.
• Redundancy requirement: 3 tank system.
• High throughput at 3500 gal/day system cost:
f $
• 3 Tank & high temperature filter skid: $1.2M
Effluent Treatment Systems – Design Considerations
BSL4 – Cost Comparison
• Relative cost of C22 – Hastelloy to 316L is 10 times.
• Relative cost of 3500 gal/day treatment system cost:
• Dual continuous flow – 316L: $1.8M
• Batch treatment – 316L: $2.0M
• Batch treatment – Hastelloy: $2.45M, approx. 22%
13
Effluent Treatment Systems – Design Considerations
Effluent Treatment Systems
• The overall system layout has to be coordinated with lab
equipment.
equipment
• Filtration system sizing and material selection
• Pipe and Tank material selection dependent on chemical,
predominately chlorine, and thermal factors.
Effluent Treatment Systems – Design Considerations
Q&A
14
Related docs
