August 2010

Prakash Parab, Director, Dulsco Waste Management Services provides an overview of key ways and means to disposing refinery waste.

UAE, due to its ample hydrocarbon reserves, has got a strong base of associated industries, like petroleum refineries. The underlying waste management philosophy of such refineries is to take all practicable measures to eliminate unnecessary waste generation by reducing waste at source, and wherever it is not practicable:

  • Process waste through the refinery effluent treatment facility

  • Recycle waste through the refinery process on-site

  • Recycle or further treat waste off-site via a reliable third party

  • Dispose off at an approved waste-disposal site

A typical refinery effluent treatment facility includes the following stages:

  • Diversion pond

  • Surge pond

  • Corrugated plate interceptor

  • Induced gas floatation unit

  • Four sequential batch reactors

  • Skimming basin

  • Tertiary treatment plant

  • Sand drying beds

  • Sewage disposal unit

  • Final holding basin

Waste which cannot be treated at the effluent treatment plant (ETP) and waste generated during different stages of the effluent treatment are disposed off at approved disposal sites. Examples of the latter include biological sludge, sand, activated charcoal and oily water. Waste that cannot be treated at ETP includes (but not limited to) the following:

  • Clay from clay filters

  • Charcoal from MEROX reactors

  • Anthracite coal

  • Spent amine

  • Activated carbon

  • Oily water and sludge after tank cleaning, which cannot be treated at the ETP 

  • Pyrophoric scale from  hydro-jetting,

  • Superfluous bitumen,

  • Insulation materials,

  • Spent acid oils, and oily water

The following chart shows the quantity of waste generated (in metric tonnes) by a petroleum refinery in Dubai between 2008 and 2010, with forecasts up to the year 2014.

Tank cleaning

The tank farm must be cleaned periodically to prevent the accumulation of waste products. The tank cleaning process consists of planning, followed by mobilisation and thereafter additional stages in the order given below: 

  • Pumping out of products: The product inside the tank need to be pumped out. Initially the pumping system prevalent at the tank farm is used to reduce to a level till it loses suction. Later, a separate pumping system, which could include a compressor and pneumatic pump, is used to empty the pump-able product. Usable product is pumped back to the system while the un-usable product is pumped into road tankers for disposal.

  • Ventilation: All piping systems are blanked so that the tank is isolated from live pipelines. Depending on the layout of man holes, a plan is made so as to provide for proper ventilation. A typical plan is illustrated below. For ventilation pneumatic blowers and eductors are used.

  • Gas monitoring: The gas is monitored inside the tank and when the levels subside to permissible limits, an entry permit is obtained with a breathing apparatus in order to commence the desludging process.

  • Desludging: Desludging is the process of removing sludge from a tank. It could be removed by a super sucker (as shown in Desludging - 1) and pumped into a vacuum skip, which can be disposed through a skip loader.

Or, it could be manually removed in bags and collected in open skips to be disposed by skip loader.

During de-sludging, continuous ventilation and gas monitoring is carried out. During manual de-sludging, the tank cleaner observes all safety regulations.

  • High-pressure washing: After the de-sludging process, high-pressure water cleaning is carried out. Proper approved scaffolding is erected, if required, to carry out the cleaning. The wash water is collected in tankers for disposal. Continuous ventilation and gas monitoring is carried out.

Waste disposal

The wastes generated can be classified into two types based on where they end up:

  • Waste for further treatment

  • Waste for disposal

    In case the waste is to be disposed off, it is important to ensure that all environment-friendly options are exhausted.

    For direct off-site disposal of regular non-hazardous waste, the same is collected in suitable containers on a regular basis and disposed by an approved contractor as per local rules and regulations.

    In the case of hazardous waste, it is collected in suitable containers, and a third-party laboratory test is conducted. Before the waste is transported to the disposal site, local rules and regulations need to be adhered and all formalities and documentation requirements need to be met. For example, if a refinery inside the Jebel Ali free Zone is considered:

    a.) Dubai Municipality HAZFORM-I is to be filled and submitted to PCFC authority for approval. Relevant and supporting information like lab test results need to be attached to corroborate the claims

    b.) An application needs to be submitted for waste disposal through the Dubai Municipality website, along with any supporting information, like the results of the third-party lab test.

    c.) Once the application is approved by the Dubai Municipality, a receipt of the same is to be procured after payment of dues.

    d.) The waste transporter then removes the waste from the client site and delivers to an approved disposal site, culminating in the submission of a proof of delivery.

    e.) The waste manifest can be closed only after obtaining all documents, like for example, gate passes, invoices, incident reports and audit reports from the waste transporters.

    (The author is Director, Dulsco Waste Management Services.  Dulsco provides waste management services (WMS) to refineries, including hazardous and non-hazardous solid and liquid waste management, tanker services, onshore and offshore tank cleaning and fabrication services. Key clients in the UAE include Emarat, ENOC, Dubai Petroleum, EPPCO and Shell)

    • © H2O 2010