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Containment and Disposal of Waste Water in HP and UHPWJ Operations. Richard A. Burgess KTA-Tator, Inc. Containment and Disposal of Waste Water in HP and UHPWJ Operations. Overview of HPWJ & UHPWJ Surface Preparation Waste Generation Issues Unique to HPWJ & UHPWJ
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Containment and Disposal of Waste Water in HP and UHPWJ Operations Richard A. Burgess KTA-Tator, Inc.
Containment and Disposal of Waste Water in HP and UHPWJ Operations • Overview of HPWJ & UHPWJ Surface Preparation • Waste Generation Issues Unique to HPWJ & UHPWJ • General Containment Design Considerations- Guide 6 • Management of Wastes Generated • Disposal Options
Overview of HPWJ & UHPWJ Surface Preparation • Equipment • Definitions and Terminology • Cleanliness Standards
Definitions and Terminology Waterjetting (WJ): Use of standard jetting water discharged from a nozzle at pressures of 70 MPa (10,000 psig) or greater to prepare a surface for coating or inspection. Water Cleaning (WC): Use of pressurized water discharged from a nozzle to remove unwanted matter from a surface.
Definitions and Terminology Low-Pressure Water Cleaning (LP WC): • Water cleaning performed at pressures less than 34 MPa (5,000 psig). This is also called “power washing” or “pressure washing.” High-Pressure Water Cleaning (HP WC): • Water cleaning performed at pressures from 34 to 70 MPa (5,000 to 10,000 psig).
Definitions and Terminology High-Pressure Waterjetting (HP WJ): Waterjettingperformed at pressures from 70 to 210 Mpa (10,000 to 30,000 psig). Ultrahigh-Pressure Waterjetting (UHP WJ): Waterjetting performed at pressures above 210 Mpa (30,000 psig).
Cleanliness Standards Joint Surface Preparation Standard SSPC-SP 12/NACE No. 5 Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating Revised July 2002 Approved 1995
Cleanliness Standards • WJ-1 Clean to Bare Substrate: A WJ-1 surface shall be cleaned to a finish which, when viewed without magnification, is free of all visible rust, dirt, previous coatings, mill scale, and foreign matter. • Discoloration of the surface may be present.
Cleanliness Standards • WJ-2 Very Thorough or Substantial Cleaning: A WJ-2 surface shall be cleaned to a matte (dull, mottled) finish which, when viewed without magnification, is free of all visible oil, grease, dirt, and rust except for randomly dispersed stains of rust, tightly adherent thin coatings, and other tightly adherent foreign matter. • The staining or tightly adherent matter is limited to a maximum of 5% of the surface.
Cleanliness Standards • WJ-3 Thorough Cleaning: A WJ-3 surface shall be cleaned to a matte (dull, mottled) finish which, when viewed without magnification, is free of all visible oil, grease, dirt, and rust except for randomly dispersed stains of rust, tightly adherent thin coatings, and other tightly adherent foreign matter. • The staining or tightly adherent matter is limited to a maximum of 33% of the surface.
Cleanliness Standards • WJ-4 Light Cleaning: A WJ-4 surface shall be cleaned to a finish which, when viewed without magnification, is free of all visible oil, grease, dirt, dust, loose mill scale, loose rust, and loose coating. • Any residual material shall be tightly adherent. (Dull Putty Knife Test)
1.4 Visual Reference Photographs: SSPC-VIS 4/NACE VIS 7, “Guide and Reference Photographs for SteelSurfaces Prepared by Waterjetting,” provides color photographs for the various grades of surface preparation as a function of the initial condition of the steel. The latest issue of the reference photographs should be used.
Pressure and Flow Rate • Pressure at Nozzle 70 MPa (10,000 psig) Flow 12.9 L/min (3.42 gpm) • Pressure at Nozzle 140 MPa (20,000 psig) Flow 8.3 L/min (2.2 gpm) • Pressure at Nozzle 280 MPa (40,000 psig) Flow 2.0 L/min (0.52 gpm)
Energy 70-MPa (10,000-psig) Jets may not significantly erode the coatings- they are typically used for partial removal or for cleaning loose detritus
Energy 140-MPa (20,000-psig) Jets erode the coatings fairly rapidly- typically used for partial removal.
Energy 280-MPa (40,000-psig) Jets erode and destroy coatings very fast -typically used when most or all of the coating is to be removed
Quantity of Waste Water PSI GPM Lbs/Hra Ft3/Hr 10,000 3.4 1700 27.4 20,000 2.2 1102 17.6 40,000b 2 260 4.2 a-A gallon of water weighs 8.34 lbs. b-At this level of energy surfaces dry quickly due to heat
Production Rates Selective stripping of outer hull coatings open-cycle, hand held lance- 39 ft2/hr/gun - 89 ft2/hr/gun. Sweep and spot “water-blast” inside of tanks with hand-held lances- 157 ft2/hr/gun - 171 ft2/hr/gun
Production Rates Sweep and spot “water-blast” of outer hull coatings with hand-held lances – Average, 198 ft2/hr/gun Complete removal of severely damaged outer hull coatings with hand-held lances- Average, 152 ft2/hr/gun
Production Rates Automated Complete removal of non-skid flight deck to bare metal closed loop machine- Average, 134 ft2/hr/unit. Complete removal of outer hull coatings to bare metal open-cycle machine- Average, 471 ft2/hr/unit.
Waste Stream Characteristics Influenced by • The condition of the existing coating • Pressures employed • Volume of water used
Waste Generation Issues Unique to HPWJ & UHPWJ • Mists and Gravity • Quantity-Flow Rate and Volume • Energy- • Fluids Slurries Sludges Solids
Mists and Gravity • Mists, droplets of water suspended in the air that can contain small particulates including pigments and particles of coating • Water flows due to gravity, just like abrasives- but water will find and collect in the lowest point- seeks it own level.
Fluids Slurries Sludges Solids • Fluid, liquid water where the solids content does not influence the flow or movement • Slurry, liquid water with suspended insoluble solids being carried and influencing flow • Sludge, wet or moist solids that settle and resist flow • Solids, mostly caked particles with little moisture content
Table W Containment Notes • Note 1: When designing a ventilation system, care must be taken to balance the static pressure with the input airflow to avoid collapsing the containment or ductwork due to high negative pressure. • Note 2: The table occasionally identifies two options for a given component. For example, containment materials (5.3.1) are shown as being either rigid or flexible. If the specifier requires the use of rigid materials only, this restriction must be specified separately. • Note 3: Class 4W will capture dislodged paint chips and debris, but will not contain the water used for cleaning. • * When vacuum shrouded waterjetting is employed, ground covers or free-hanging tarpaulins may provide controls equivalent to Class 1W.
Management of Wastes Generated • What are the characteristics of the Coating (brittle, soft, loose, thick or thin, layers) • Constituents of Coating (lead, no-Lead, other metals, asbestos, etc. ) • Service Environment (urban, watershed, public use, industrial use, etc.) • Waste stream characteristics (liquid, slurry, sludge, solids)
Total and Dissolved Heavy Metals Separating Lead in Wash Water by Physical Means Example- All Lead • 100 grams in Wash Water 100% • 80 grams in Screened Wash Water 80% • 18 grams in Filtered (5µ) Wash Water 18% • 0.24 grams are dissolved metal 0.24% Dissolved Metals, 0.45µ filter
Full Containment and Collection • Designed to keep water from storm drains and running off site- portable containment pools or pits • Manufactured wastewater collection systems- pits to close-loop self contained units • Wet/dry vacuums, sump pumps, diaphragm pumps
Collection and Handling Options • No collection required, separation of solids from the liquid by screen or geo-textile. Retention requirement for solids. • Collection required, separation of large solids, filter to remove small solids. Test and open discharge. • Collection required, separation of large solids, filter to remove small solids. Test and controlled discharge.
NON-LEAD BASED PAINT REMOVAL PROJECTS(Example) Water washing of the bridge for the purpose of removing chalk, dirt, grease, oil, bird nests, and other surface debris can be performed without additional containment provided paint chips and removed debris are removed and collected prior to washing or are cleaned from the site after cleaning is completed each day. At the Contractor’s option, SSPC Class 4W permeable containment materials described above under “Water Jetting or Wet Abrasive Blast Cleaning for the Removal of Paint” can be used to collect the debris while the washing is underway.
LEAD BASED PAINT REMOVAL PROJECTS(Example) Water washing of the bridge for the purpose of removing chalk, dirt, grease, oil, bird nests, and other surface debris, and water jetting or wet abrasive blast cleaning for the purpose of removing paint and surface debris shall be conducted within a containment designed, installed, and maintained in order to capture and contain all water and waste materials. (SSPC Class 2W-3W) When water is used for surface cleaning, the collected water shall be filtered to separate the particulate from the water. Recycling of the water is preferred in order to reduce the volume of waste that is generated. The water after filtration shall be collected and disposed of according to the waste handling portions of this specification. When a slurry is created by injecting water into the abrasive blast stream, the slurry need not be filtered to separate water from the particulate.
LEAD PAINT REMOVAL PROJECTS(Example) Waste water generated from bridge washing, hygiene purposes, and cleaning of equipment shall be filtered on site to remove particulate and disposed of at a Publicly Owned Treatment Works (POTW) according to State regulations. The Contractor shall provide the Engineer with a letter from the POTW indicating that they will accept the waste water. If the POTW allows the filtered water to be placed into the sanitary sewer system, the Contractor shall provide a letter from the POTW indicating that based on the test results of the water, disposal in the sanitary sewer is acceptable to them. Water shall not be disposed of until the above letter(s) are provided to, and accepted by, the Engineer.
Recycling Water • Minimize water consumption • Minimize waste quantities • Cleaning Recycled Water
Waste Streams • Waterjetting Waste Water • Hygiene Water • Screened solids • Filtered Solids, Filters
Waste Water DisposalMost Common Practices • Permission to discharge to a POTW sanitary sewer line- Discharge limits (0.4 to 1.0 mg/L) • Permission to truck water to the POTW • Obtain Permit to discharge to stream, creek, etc.- not likely to be feasible- Client’s permit does not necessarily cover contractors waste stream
Waste Water Disposal Some Uncommon Practices • Fixed Facility Operations Natural Evaporation of Waste Water (CAP) On-site Treatment and discharge (Treatment Plant) Drying, Sludge Cake