10.1.1 When the EGC system is operated in ports,
harbours, or estuaries, the washwater monitoring and recording should
be continuous. The values monitored and recorded should include pH,
PAH, turbidity and temperature. In other areas the continuous monitoring
and recording equipment should also be in operation, whenever the
EGC system is in operation, except for short periods of maintenance
and cleaning of the equipment. The discharge water should comply with
the following limits:
10.1.2.1 The washwater pH should comply with one
of the following requirements which should be recorded in the ETM-A
or ETM-B as applicable:
-
(i) The discharge washwater should have a pH of
no less than 6.5 measured at the ship’s overboard discharge
with the exception that during manoeuvring and transit, the maximum
difference between inlet and outlet of 2 pH units is allowed measured
at the ship’s inlet and overboard discharge.
-
(ii) During commissioning of the unit(s) after
installation, the discharged washwater plume should be measured externally
from the ship (at rest in harbour) and the discharge pH at the ship’s
overboard pH monitoring point will be recorded when the plume at 4
metres from the discharge point equals or is above pH 6.5. The discharged
pH to achieve a minimum pH units of 6.5 will become the overboard
pH discharge limit recorded in the ETM-A or ETM-B.
10.1.3 PAHs (Polycyclic Aromatic Hydrocarbons)
10.1.3.1 The washwater PAH should comply with
the following requirements. The appropriate limit should be specified
in the ETM-A or ETM-B.
10.1.3.2 The maximum continuous PAH concentration
in the washwater should not be greater than 50 μg/L PAHphe (phenanthrene
equivalence) above the inlet water PAH concentration. For the purposes
of this criteria, the PAH concentration in the washwater should be
measured downstream of the water treatment equipment, but upstream
of any washwater dilution or other reactant dosing unit, if used,
prior to discharge.
10.1.3.3 The 50 μg/L limit described above
is normalized for a washwater flow rate through the EGC unit of 45
t/MWh where the MW refers to the MCR or 80% of the power rating of
the fuel oil combustion unit. This limit would have to be adjusted
upward for lower washwater flow rates per MWh, and vice-versa, according
to the table below.
|
Flow Rate (t/MWh)
|
Discharge Concentration Limit(μg/L PAHphe equivalents)
|
Measurement Technology
|
| 0 – 1
|
2250
|
Ultraviolet
Light
|
| 2.5
|
900
|
– ” –
|
| 5
|
450
|
Fluorescencefootnote
|
| 11.5
|
200
|
– ” –
|
| 22.5
|
100
|
– ”
–
|
| 45
|
50
|
– ”
–
|
| 90
|
25
|
– ”
–
|
10.1.3.4 For a 15-minute period in any 12-hour
period, the continuous PAHphe concentration limit may exceed
the limit described above by up to 100%. This would allow for an abnormal
start up of the EGC unit.
10.1.4 Turbidity/Suspended Particle Matter
10.1.4.1 The washwater turbidity should comply
with the following requirements. The limit should be recorded in the
ETM-A or ETM-B.
10.1.4.2 The washwater treatment system should
be designed to minimize suspended particulate matter, including heavy
metals and ash.
10.1.4.3 The maximum continuous turbidity in washwater
should not be greater than 25 FNU (formazin nephlometric units) or
25 NTU (nephlometric turbidity units) or equivalent units, above the
inlet water turbidity. However, during periods of high inlet turbidity,
the precision of the measurement device and the time lapse between
inlet measurement and outlet measurement are such that the use of
a difference limit is unreliable. Therefore all turbidity difference
readings should be a rolling average over a 15-minute period to a
maximum of 25 FNU. For the purposes of this criteria the turbidity
in the washwater should be measured downstream of the water treatment
equipment but upstream of washwater dilution (or other reactant dosing)
prior to discharge.
10.1.4.4 For a 15-minute period in any 12-hour
period, the continuous turbidity discharge limit may be exceeded by
20%.
10.1.5.1 The washwater treatment system should
prevent the discharge of nitrates beyond that associated with a 12%
removal of NOx from the exhaust, or beyond 60 mg/l normalized
for washwater discharge rate of 45 tons/MWh whichever is greater.
10.1.5.2 At each renewal survey nitrate discharge
data is to be available in respect of sample overboard discharge drawn
from each EGC system with the previous three months prior to the survey.
However, the Administration may require an additional sample to be
drawn and analysed at their discretion. The nitrate discharge data
and analysis certificate is to be retained on board the ship as part
of the EGC Record Book and be available for inspection as required
by Port State Control or other parties. Requirements in respect of
sampling, storage, handling and analysis should be detailed in the
ETM-A or ETM-B as applicable. To assure comparable nitrate discharge
rate assessment, the sampling procedures should take into account
paragraph 10.1.5.1, which specifies the need for washwater flow normalization.
The test method for the analysis of nitrates should be according to
standard seawater analysis as described in Grasshoff et al.
10.1.5.3 All systems should be tested for nitrates
in the discharge water. If typical nitrate amounts are above 80% of
the upper limit, it should be recorded in the ETM-A or ETM-B.
10.1.6 Washwater additives and other substances
10.1.6.1 An assessment of the washwater is required
for those EGC technologies which make use of chemicals, additives,
preparations or create relevant chemicals in situ. The
assessment could take into account relevant guidelines such as resolution MEPC.126(53), procedure for
approval of ballast water management systems that make use of active
substances (G9) and if necessary additional washwater discharge criteria
should be established.