Evaluating the Performance of Shipboard Oil/Water Separators

Transcription

1 Evaluating the Performance of Shipboard Oil/Water Separators Debra Falatko Vice President, Oceans and Coastal Protection Eastern Research Group, Inc. 01/14/2009 June 24,

2 OWS Performance Data Uniform National Discharge Standards (UNDS) OWS sampling onboard armed forces vessels conducted in late 1990s/early 2000s Vessel General Permit (VGP) Study of Bilgewater Treatment System Effectiveness OWS sampling onboard large commercial vessels conducted in 2012 Paper published in Environmental Science and Pollution Research: 2

3 UNDS Section 312(n) of the CWA requires EPA and DoD to promulgate uniform national discharge standards for certain discharges incidental to the normal operation of a vessel of the Armed Forces Surface Vessel Bilgewater/Oil- Water Separator Effluent identified as one of the 25 Discharges requiring control Performance standards for bilgewater have not yet been proposed or promulgated, nor have regulations governing the design, construction, installation, and use of a Marine Pollution Control Device 3

4 UNDS OWS Sampling Support to Naval Surface Warfare Center, Carderock Division 7 ships sampled variety of propulsion systems In port or underway Variety of OWS and/or polisher combinations System influent, effluent, intermediate points Isokinetic sampling with paired influent/effluent Analyzed for classicals (e.g., O&G, TSS, BOD), metals, organics, pesticides 4

5 UNDS OWS Sampling Ship USS CARNEY DDG 64 (Guided missile destroyer) USS BONHOMME RICHARD LHD 6 (Landing Helicopter Dock) USS RUSHMORE LSD 47 (Landing Ship Dock) USS DAVID R RAY DD 971 (Destroyer) USS MAHAN DDG 72 (Guided missile destroyer) USS OAK HILL LSD 51 (Landing Ship Dock) USCGC MORGENTHAU WHEC 722 (CG Cutter) Propulsion System Sampling OWS System Gas turbine Underway Parallel-plate coalescing gravity separator + ceramic membrane polisher Conventional Underway Parallel-plate coalescing steam turbine gravity separator Diesel In port Parallel-plate coalescing gravity separator + ceramic membrane polisher Gas turbine Underway Parallel-plate coalescing gravity separator Gas turbine Underway Parallel-plate coalescing separator + polymeric membrane polisher Diesel In port Parallel-plate coalescing gravity separator Gas turbines and diesel Underway Duplex-type strainer + single stage/gravity coalescing gravity separator 5

6 UNDS OWS Sampling Results See Attachment 1 6

7 VGP 2006 court order revoked EPA regulation excluding discharges incidental to the normal operation of a vessel from NPDES permitting EPA issued the Vessel General Permit in 2008 (reissued in 2013) to provide NPDES permit coverage for discharges from commercial vessels greater than 79 feet Bilgewater is one of 27 permitted discharges 7

8 VGP OWS Sampling Support to EPA s VGP Program 3 ships sampled in port Treatment systems believed to be among the best technologies available type approval data below 5 ppm oil Grab samples of paired influent and effluent Analyzed for classicals (e.g., O&G, TSS, BOD), metals, organics, surfactants Oil content analysis using 4 methods 8

9 VGP OWS Sampling Ship Container ship 50,000 GT, 4,000 TEU Container ship 50,000 GT, 4,000 TEU Bulk carrier (Canadian Laker) 23,000 GT OWS System Gravity OWS + 2 polishing media filters in series (JOWA 3SEP OWS + JOWA SEAGUARD OCM) Heat exchanger + gravity OWS + coagulation/flocculation/flotation + granular media filter + activated carbon polishing filter (Marinfloc Model CD02 +Deckma OMD-2005 OCM) Strainer + heat exchanger + high-speed centrifugal OWS (Alfa Laval Pure Bilge + Deckma OCM) 9

10 VGP OWS Sampling Results See Attachment 2 10

11 OWS Reliability Systems must be well maintained and operated. Some systems can be easily fouled, increasing consumables requirements (e.g., sorbent media). Ship movement exacerbates. May require continuous operator observation during use. Some operators prefer shoreside management. 11

12 OCM Accuracy ERG (2004) assessed available data published by the U.S. Navy to assess OCM accuracy. Compared 125 OCM readings with corresponding effluent oil concentrations and found no correlation (coefficient of determination, r2=0.0012). McLaughlin et al (VGP sampling) found OCM readings more variable than actual oil concentrations, resulting in false negatives and false positives. Onboard bulk carrier, OCM during first sample was 0 ppm, ranged from 5-16 ppm during second sample, returned to 0 ppm for third through fifth samples after cleaning OCM. 12

13 OCM Reliability Bilgewater is complex mixture of fluids that is difficult to monitor, especially at low oil concentrations. Ultrasonic turbidity measurements prone to interference by suspended solids, soot (measured as oil). UV fluorescence technology resistant to interferences, but 10x cost. Require frequent maintenance and cleaning to avoid malfunction and erroneous readings, including exchange of cells every 3-4 mo. Require annual calibration. Reported accuracy typically ± 5 ppm, which makes readings questionable. Meeting 5 ppm oil standards is possible, but requires serious commitment to acquiring and maintaining effective separators and OCMs, and to proper design of holding tanks (e.g., oil skimming, suction from bottom of tank). 13