Improvements in Oily Sludge Management at KNPC
Sr. Environment Emgineer,
Kuwait National Petroleum Company, Kuwait
Abstract : Disposing oily sludge in large earthen sludge pits is a common enough
practice in Kuwait and other parts of oil rich Middle East. Since early eighties, KNPC
used two unlined pits for disposing oily sludge from its Refinery operations. This
paper discusses how this process was discontinued and an environment – friendly
approach towards sludge management was adopted at KNPC. The Strategy
involved recovering oil from the sludge thus achieving value addition and waste
volume reduction. The technology employed was a three phase centrifuge to
separate oil, water and solid with additional centrifuging to remove residual solids
and water from the recovered oil. Sludge pit operation has been stopped and the
pits have been remediated using a mixture of techniques/technology like oil
recovery, evaporation, mechanical treatment of residual sludge and further
treatment of soil by Anaerobic Thermal Adsorption.
Public Authority of Industry in Kuwait had leased two sites in West Shuaiba
Industrial Area since early eighties, for use by Kuwait National Petroleum Company
to dispose oily sludge in two unlined pits. The disposed oily sludge has significant
hydrocarbon content. Evaporation of the lighter component of the oil affected spring
camps and some of the industrial workers residing nearby. Over the years, these
pits became full and started overflowing during rains resulting in contamination of
land around the pits.
Kuwait National Petroleum Company initiated actions to identify options for
management of oily sludge and do away with the sludge pits as these pits had
started overflowing posing risk of contamination of surrounding area.
After taking stock of the situation, the following priorities were established.
a) Identify and establish a facility to treat the oily sludge generated from the
three refineries and local marketing.
b) Cease usage of the existing sludge pits, assess the sludge pits’ content &
start recovery of oil.
c) Identify and implement suitable strategy for remediation of the pits. The
Main objective of the initiative was to manage the oily sludge generated from
KNPC facilities in an environment friendly manner.
Various options were evaluated before finalizing the strategies. Some of the options
evaluated were in situ chemical / bio treatment in tanks followed by bio remediation
of residual sludge, with a mobile treatment unit or a common fixed facility.
For existing sludge pits options like recovery of water and oil which could be
transferred to refineries using activated carbon based treatment technology for
recovered oil and water were looked into. It was found during the evaluation that top
free layer of oil could be blended to fuel oil. Based on these findings following
objectives and strategies were decided by KNPC Management.
a) Establish a common permanent Sludge Treatment Facility at Mina Abdulla
Refinery (MAB Refinery).
b) Recover the free oil from existing sludge pits & use as fuel oil blend and
remediation of the existing pits & soil to bring hydrocarbon content below
Sludge Treatment Facility
Sludge is generated when a storage tank is decommissioned for cleaning and
maintenance. Sludge generation from tanks is not continuous, huge quantity is
generated when a tank is decommissioned for cleaning / maintenance. For sludge
treatment, industry practice is to hire sludge treatment services when a tank is taken
up for maintenance. It was decided to develop a facility which can add contribute in
solving this issue of national importance.
One of the first problems faced was fixing the capacity of the sludge handling facility
as it is difficult to assess the quantity and quality of sludge to be generated. This
was overcome by
i) Installing two trains in place of one to have better turndown ratio.
ii) Sizing the unit for 8 hours single shift operation with flexibility to operate on
extended time, two shift or round the clock based on sludge availability.
iii) Providing adequate storage to maintain consistent sludge feed.
The technology uses three phase centrifuge for the separation of Oil, Water and
Solid from the sludge. The sludge is preheated above 80 deg. C before being fed to
three phase centrifuge. Recovered oil is further centrifuged to remove any residual
sediment & water. Water from the centrifuge is routed to baffle tanks to remove oil
Sludge Treatment Facility
Remediation of existing sludge pits
Remediation of existing sludge pits had its own challenges. One of the first
challenges was assessment of sludge pit (180m long, 175m wide and 8m deep)
contents and composition. Sampling of sludge pits from different locations was
carried out using heavy duty cranes. Results indicated top layer of free oil 2.1
meters in thickness, water layer of 5.1 meters and balance of sludge at the bottom
of the pits.
Samples of the top layer of free oil were taken and analyzed. The results showed
that if recovered, this oil can be blended in fuel oil. This opened the prospects of
transferring part of free oil to KNPC’s own refineries. As an extension of the idea,
option of disposing water to existing effluent treatment plants of refineries followed
by natural remediation of site was looked into. However, the idea was not pursued
considering the logistics for transferring all contents to refinery and land requirement
for natural remediation.
Analysis of sludge pit sump
Other methods/options for remediation were looked at in depth. A Private service
provider was employed to chalk out a plan for Remediation of the pits. It was also
decided that after having absorbed the recovered oil in refinery fuel oil stream, the
balance will be shared with the private party to finance the remediation of the site.
M/S National Cleaning Company, who were managing the industrial waste disposal
facility owned by Public Authority of Industries of Kuwait, were contracted to execute
the remediation project.
The problem of managing the sludge during interim period when the sludge pits
were closed and before the sludge treatment facility was operational posed another
challenge. The problem was over come by earmarking two of the product tanks for
interim storage and not scheduling major tank maintenance during the period.
With the installation and commissioning of Sludge Treatment Facility, the main
objective of management of oily sludge generated at KNPC Refineries in
environment friendly manner has been achieved. The Environmentally damaging
practice of disposal of petroleum sludge in the open pits which has been in practice
for years has been stopped.
The key benefits realized from the initiatives are:
1. Conservation of Natural Resources: More than 20415 m3 of oily sludge been
treated at Sludge Treatment Facility since its commissioning in January 2005. It is
worth mentioning here that now Sludge treatment capacity is available for utilization
by the oil industry in Kuwait. Kuwait Oil Company, the main Exploration and
Production Company of Kuwait have shown interest in utilizing this state of the art
treatment facility. This has resulted in tremendous volume reduction in disposed
sludge quantities. Sludge
2. The value of oil recovered during the period January 2005 to Dec 2006, was
501620 KD against an operating cost of 305095 KD. This resulted in an earning of
196525 KD during the period and thus demonstrates project sustainability.
3. Risk of groundwater contamination in the area of location of the sludge pit has
been reduced considerably .
4. Remediation of 1000 m2 of contaminated land has been carried out making the
land available for other purposes.
Pits before Project Pits after Project
5. Elimination of odor problems and fugitive emission from the pits in the area. This
has also eliminated safety & health hazards to the people and the site will be
available for use for other purposes.
6. It has highlighted the opportunities for oil recovery from oily sludge to all other
members of the oil industry in the State of Kuwait.