| Overview: |
The Naval Facilities Engineering
Service Center has developed a shore-side system for treating bilge and
other oily wastewaters in addition to designing a 50-gpm mobile system.
The Bilge and Oily Wastewater Treatment System (BOWTS) separates oil,
grease, and heavy metals found in bilge and oily waters. BOWTS has the
capability to lower the contaminant levels to less than the permissible
limits for discharge into publicly owned treatment works (POTWs).
The BOWTS shore-side systems have successfully
operated at Naval Shipyard Long Beach, Naval Air Station Alameda, Fleet
Industrial Support Center Oakland, Naval Station Pearl Harbor, Naval
Station Guantanamo Bay, Naval Station Guam, Naval Station San Diego,
Submarine Base San Diego, Naval Construction Battalion Center, Port
Hueneme and the Naval Station Roosevelt Roads, Puerto Rico. Mobile systems
also were shipped to Yokosuka and Sasebo Japan in September
1999.
The ship's bilge water is transferred to a
large load equalization tank, equipped with a skimmer for removal of bulk
free product. After sufficient residence time, the water fraction is
selectively removed and fed through a plate coalescer for mechanical
removal of free oil. The water then passes through mixing chambers where
chemical treatment is performed.
Three chemical metering pumps feed a reverse
emulsion breaker, sodium hydroxide, and anionic polymer into the mixing
chambers to breakdown the emulsion, precipitate the heavy metals, and floc
the solids. The effluent is then pumped into an induced-air flotation
unit, where all the solids generated by the process are removed. Two slop
oil tanks are provided for collecting the free oil separated in the load
equalization tank and the oil/water separator, and a sludge tank is
provided for holding the sludges collected in the oil/water separator and
the induced-air flotation device. The water fraction leaving the system
will be of sufficient quality to be discharged directly into the sanitary
sewer.
Although the pollutants found in ship bilge and
other oily wastewaters vary from ship to ship, NFESC applied a strategy to
categorize and quantify the principal pollutants. The data collected was
used in designing the basic BOWTS. Additional process units could be added
where local discharge requirements indicate the need for more rigorous
treatment than is available from the basic system design.
|
| Compliance Benefit: |
The use of a bilge and oily
wastewater treatment system can help facilities meet pretreatment
standards for discharges of wastewater into a POTW (40 CFR 403) or
meet effluent limits of a NPDES permit (40 CFR 122). In addition,
this treatment process may help facilities meet the requirements of waste
reduction under RCRA, 40 CFR 262, Appendix.
The compliance benefits listed here are only
meant to be used as a general guideline and are not meant to be strictly
interpreted. Actual compliance benefits will vary depending on the factors
involved, e.g., the amount of workload involved.
|
| Materials Compatibility: |
No materials compatibility
issues were identified.
|
| Safety
and Health: |
BOWTS chemicals are irritants
to skin, eyes, and mucous membranes. Inhalation of these fumes can be
dangerous. Proper personal protection equipment is, therefore,
recommended.
Consult your local industrial health
specialist, your local health and safety personnel, and the appropriate
MSDS prior to implementing this technology.
|
| Benefits: |
- BOWTS can recover oil for recycling.
- BOWTS is a proven off-the-shelf
technology.
- The system is sufficiently flexible to
accommodate a wide range of concentrations and flow ranges; each system
can be tailored to site-specific requirements (e.g.,
configuration, modifications, etc.).
- The BOWTS requires only one or two people to
operate and monitor the process.
|
| Disadvantages: |
- Not an economical alternative for activities
generating less than one million gallons of ship’s bilge and oily
wastewater annually.
|
| Economic Analysis: |
The BOWTS design is unique for
each activity and reflects selection of hundreds of component parts
designed for automatic operation within the activity’s infrastructure. The
following analysis is based on data provided by Naval Station San
Diego.
Assumptions:
- The system processes 15 million gallons of
wastewater annually.
- Traditional methods require transport of
large volumes of oily wastewater for treatment/disposal at a cost of
$0.24/gallon.
- Cost figures for the BOWTS system are actual
budgetary allocations for each activity provided by Naval Station San
Diego.
Cost Comparison for BOWTS
System vs. a Traditional Disposal System
| |
Traditional
System |
BOWTS |
| Capital and
Installation Costs: |
$0 |
$1,400,000 |
| Operational
Costs: |
|
|
| Operation and
Maintenance Costs: |
$0 |
$300,000 |
| Waste Treatment
and Disposal Costs: |
$3,600,000 |
$77,000 |
| Utility Costs
(electricity, sewer): |
$0 |
$140,000 |
| Permitting and
Lab Analysis Costs: |
$0 |
$24,000 |
| Total
Costs (not including capital and installation costs): |
$3,600,000 |
$540,000 |
| Total
Income: |
$0 |
$0 |
| Annual
Benefit: |
-
$3,600,000 |
-$540,000 |
Economic Analysis Summary
Annual Savings for BOWTS:
$3,060,000
Capital Cost for Diversion Equipment/Process:
$1,400,000
Payback Period for Investment in Equipment/Process: < 6
months
Click Here to view an Active
Spreadsheet for this Economic Analysis and Enter Your Own Values. To
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in the Tool Bar.
|
| Approving Authority: |
Implementation of the BOWTS
technology requires coordination between major claimant, the base
environmental office, and a contracting vehicle. Approval is controlled
locally and should be implemented only after engineering approval has been
granted. Major claimant approval is not required.
|
