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Hazards of Oily Waste & its Remediation

Lecture

atDepartment of continuing education IIT, Roorkee

27th January, 2010

G.S. Danggurbax49@gmail.com

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Presentation Outline

Oily Wastes / Hazardous Wastes

Sludge Generation/ Environmental Regulations

Sludge Management / Bioremediation

Other disposal ways

Conclusion

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Oily Wastes

Crude oil spills

Oily sludge generated in crude oil tanks in oil fields

and in refineries

Oil contaminated soil / drill cuttings

Oil sludge generated in petroleum product tanks in

refineries / marketing terminals

Sludge generated in effluent treatment plants (ETPs)

in refineries / oil installations

Sources:

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Oily Sludge- Constituents

It is a mixture of heavy hydrocarbons like asphaltenes and waxes together with sand, clays, water and other solid substances like rust and heavy metals

The sludge is an environment hazard & hazardous

waste rules apply on it

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Hazardous Waste Definition (As defined in HW Rules 2008)

Any waste which by reason of any of its physical,

chemical, reactive, toxic, flammable, explosive or

corrosive characteristics causes danger or is likely to

cause danger to health or environment whether alone or

when in contact with other wastes or substances is termed

Hazardous

and shall include Wastes listed in Schedule–1 (list of

processes generating waste), Schedule – 2 (concentration

limits of wastes) of HW Rules

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Sludge Generation in Refineries / Oil Installations

Oily Sludge - Generated from cleaning of the crude oil and heavy product storage tanks and also from ETP basins

Chemical Sludge – Generated in ETP during

chemical treatment of effluents. (eliminated with

commissioning of biological treatment plant, BTP)

Bio Sludge – Generated from clarifier in BTP during

biological treatment of effluents

Sludge is extremely difficult to remove from tanks & poses very difficult disposal problems

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Oily Sludge(s) – Composition

Typical high volume hazardous waste generated by refineries / storage terminals

Tank Bottoms Sludge contains Crude oil / Product Oil 40 to 80%

Tanks (FO/Diesel) Water 10 to 40%

Solids 5 to 15%

Waste Water Treatment Plant Sludge contains ETP Sludge oil 40 to 60% Emergency Basin / Lagoons water 50 to 55%

Solids 10 to 15%

Industry average for total refinery solids production is around 0.32 Ton (oil + solids) per 1000 bbl of crude processed (API study)

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Prevailing Environmental Regulations

Facility operator to obtain authorization for handling / storage / transportation of sludge

Authorization is subject to satisfactory steps taken to reduce waste generated

Occupier is responsible for treatment of hazardous waste & disposal of residual waste

Storage of raw sludge is temporarily permitted in secured landfill for a period at the end of which it is to be treated & disposed off as a part of environmentally sound management of hazardous waste

Hazardous waste (Management & Handling rules – 2008) requires refineries / oil establishments

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Management of Oily Sludge

Approach followed :

Volume reduction

Treatment for recovery of oil

Disposal of residual sludge / solids without affecting

environment

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Volume reduction / oil recovery

In-situ recovery

Operation of side entry mixers – dispersing the

sludge particles in the bulk of the crude oil

Sludge dissolving by hot gas oil (70–80oC) circulation

in the tank

Contd…Management of Oily Sludge

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Ex-situ recovery

Sludge is removed to melting pit

Melting of oily sludge by heating to 80-90oC using low

pressure steam, followed by filtering, centrifuging &

settling

Contd…Management of Oily Sludge

For ETP sludge volume reduction and dewatering is done through use of thickeners & centrifuges

With this treatment solid content of sludge is increased from 1-3% by weight to approximately 20% by weight

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The recovered oil is pumped to slop tanks for

reprocessing with crude oil. Water phase is sent to

effluent treatment plant (ETP)

Contd…

The residual sludge is disposed off / stored in specially constructed pits / secured land fill (SLF) having polymer lining and leachate collection system

Management of Oily Sludge

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Limitations of Existing Practices

Recovery of oil is limited. Residual sludge in melting pit contains oil upto 30 to 35 %wt

Substantial quantity sludge is to be removed manually (messy operation)

Leads to pollution due to VOC emissions

Manual operation is not only unhealthy / unsafe but leads to outage of tanks for very long period (8 to 15 months)

Residual sludge is problem for eco-friendly disposal

Accumulation / storage of sludge in lined pits (secured landfill is not solution on long term basis)

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Sludge Management – Bioremediation Method

Residual sludge disposal

Bioremediation of residual sludge is well reorganized /

adopted by refineries and oil producing companies as

the way to dispose it in environment friendly way

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Bioremediation of Residual Oily Sludge

Bioremediation is a process that employs microorganisms capable of degrading toxic contaminants present in hazardous wastes like oily sludge etc

Naturally occurring microorganisms transform

harmful substances containing hydrocarbons to

carbon dioxide and water

Safe disposal of sludge without affecting the quality

of soil and ground water

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Bioremediation Methodology

Oily sludge is spread over the soil of the earmarked site and tilling is carried out

Bacterial consortium (oil zapper / oilivorous’S’) is applied along with nutrient at the farmed out site

The area is tilled every fortnight in 12-16 weeks, all the oil gets decomposed to carbon dioxide and water

Soil & sludge samples are analyzed every quarter for parameters including heavy metal content. No built up of concentration of heavy metals (Zn, Mn, Cr, Cu, Ni, Pb, Co, As, Cd, Se) in the soil

Around 16 weeks of initial application the cycle is complete and fresh cycle can be started. No adverse impact on quality of ground water

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Phytoremediation

Bioremediation has been broadly successful with petroleum based constituents

Microbial digestion however has met limited success for widespread residual organic and metal pollutants

To remove trace concentration of heavy metals from soil and water phytoremediation using certain plants is fast emerging

Type of phytoremediation techniques include phytoextraction, phytotransformation, phytostabilization, phytodegradation and rizofiltration

Phytoremediation is well suited for use at very large field sites where other methods of remediation are not cost effective or practicable

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Advantages of Bioremediation

A way to safe disposal of oily sludge in petroleum industry (conventional methods expensive and cumbersome)

Bioremediation produces harmless products like carbon

dioxide, water and cell biomass

Technology well accepted in industry

Commercially used for large quantities of sludge

(>20,000 MT)

Cost effective vis-à-vis available technologies

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Disadvantages of Bioremediation

A Bioremediation is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid and complete degradation

Bioremediation often takes longer than other treatment

options, such an excavation and removal of soil or

incineration

Regulatory uncertainty remains regarding acceptable

performance criteria for bioremediation. There is no

accepted definition of “clean”, evaluating performance of

bioremediation is difficult, and there are no acceptable

endpoints for bioremediation treatments

Other disposal ways

for

hazardous wastes

Incineration

• Incineration is applied to certain wastes that cannot be recycled, reused or safely deposited in a landfill.

• Incineration is high temperature, thermal oxidation process in which hazardous wastes are converted, in presence of oxygen in the air, into gases and incombustible solid residue. Gases are vented into atmosphere through Gas cleaning system and solid residue go to landfill

Incineration

Applicability of incineration of hazardous waste depends on certain considerations:

• The waste is biologically hazardous• It is resistant to biodegradation and persistent• It is volatile and therefore easily dispersed• It cannot be safely disposed into landfill even after

stabilization• Volume reduction of waste is necessary

Incinerable wastes

Typical wastes that would need to be incinerated by the operator of TSDF (waste treatment facility ) may include

- solvent wastes (spent solvents)- waste oils, oil emulsions- oil mixtures / Refinery waste

- Others with calorific value > 2500 Kcal/kg

Guidelines for Incineration

Incineration aims - destroying the toxicity of wastes and get products of combustion that are harmless. The 3 Ts of combustion are:\

• Temperature• Time• Turbulence

Availability of oxygen is additional parameter which forms an integral part of the incineration system.

Guidelines for Incineration

When waste is burnt at the higher temperature destruction would be complete and formulation of un-burnt waste, formation of organic by-products etc would be eliminated. The longer the waste is held at high temperature, the greater will be the degree of destruction and the less likelihood of formation Products of Incomplete Combustion (PICs)

Guidelines for Incineration

Temperatures of 900-1100 C for hydrocarbon wastes and 1100-1200 C for certain waste like PCBs, waste Oil residues etc. For other halogenated organics case to case tackling may be needed.

Minimum gas phase residence time of 2 seconds has to be maintained

Combustion air – 100% excess of stochiometric requirements

Turbulence is achieved through good incinerator design

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Conclusion

Oily wastes generated in refineries / oil installations are hazardous as per HW rules 2008

Management of oily wastes include recovery of valuable oil and separating the hazardous constituents

Hazardous constituents need to be handled / disposed off in a way that the environment pollution is minimum

Bioremediation is one such way to convert the hazardous constituents into harmless products to a greater extent

Research is still on to make the bioremediation process as clean as possible

Bioremediation/ Phytoremediation techniques are improving as greater knowledge & experience are gained

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Tel: 0135-265498909997168805

E-mail : gurbax49@gmail.com

C O N T A C T S

Melting Pit

PVC LINED PIT FOR OILY SLUDGE

STORAGE

TILLING OPERATION DURING BIOREMEDIATION

SAMPLE BEFORE AND AFTER BIOREMEDITATION

oily sludgeysoil sample after bioremediation

PHYTO EXTRACTION