Full-scale STARx (Ex Situ) HottpadTM System to Treat Oil-Water Separator Sludge and Hydrocarbon-Impacted Soils

Oil and Gas Terminal Facility in South East Asia

The subject site is an operating oil and gas terminal in south east Asia. A full-scale STARx HottpadTM system was deployed to treat oil-water separator sludge as a lower cost alternative to off-site disposal. The system consisted of six modular HottpadTM units equipped with heating elements for ignition and an air distribution system to support the smoldering combustion reaction. Each unit measured 4.65 meters (m) by 2.8m to give a total system footprint of approximately 78 square meters (m2) (IMAGE 1). Ancillary equipment associated with the system included blowers for air delivery, a vapor collection system, and a control system for heater operation and air flow control.

Image 1: Six unit HottpadTM system to give a total system footprint of approximately 78m2.

System Description

The sludge was removed from the separator lagoon and mixed with Oil-Impacted Soils (OIS) in batches to create a mixture that will readily smolder (IMAGE 2). Each batch of the mixture was then placed on the HottpadTM system for treatment. The pile was covered with a clean soil cap, to act as a heat sink, and a vapor collection system prior to initiation of smoldering.

Image 2: Sludge placed within site soils prior to mixing.
Table 1: Characteristic soil analytical data demonstrating excellent treatment efficiency

Mixtures of varying sludge content and piles of varying heights were processed to evaluate the performance of the system. Soils concentrations before and after treatment were compared to assess treatment effectiveness, and in-pile temperatures and emissions were monitored to track the treatment process. Analytical data shows excellent treatment efficiency (TABLE 1). These data were confirmed through visual comparison of the mixture before and after system operation (IMAGE 3).

Image 3: Photographs of a materials before (top) and after (bottom) processing demonstrating complete and uniform treatment.


The STARx technology is a rapid, safe, and low cost treatment option for oil-water separator sludge and hydrocarbon-impacted soils.
The HottpadTM system installed in South East Asia:

  • Demonstrated self-sustaining smoldering combustion (i.e., no energy input into the system following ignition);
  • Is a lower cost alternative to traditional sludge disposal practices;
  • Reduced sludge concentrations to non-detect levels demonstrating excellent treatment efficiency.

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