Hard work for the microbes: Soil remediation in a tank farm
In a tank farm in Belém (Brazil) the soil was found to be highly contaminated. With the help of a biological process this soil is remediated by microbes and then reused at the site. Because the process was originally developed in Germany, it had to be adapted to suit the local climate. The entire operating crew are subject to the tank farm's technical safety regulations, which comply with international standards and are strictly implemented.
(01.06.2010) As many reports on the subject testify, environmental protection is by no means limited to highly-developed economic regions. Many emerging nations have now realised that sustainable development with access to global business requires them to carry out preventive and restorative environmental protection. However, it quickly becomes clear that this takes some time from a technical aspect, not to mention the time taken before decisions are made in the first place. Mercosul is an emerging economy. This South American economic bloc covers an area of more than 13 million square kilometres and has a population of about 250 million. The economic zone includes the vast areas of Brazil and Argentina, both of which are rich in raw materials. Brazil has taken a leading role in Mercosul in terms of environmental protection. This is impressively manifested in the population's demand for a clean environment, which is, in fact, stipulated in the state constitution. The following report aims to explain whether and how this environmental protection and the occupational safety that is applied are implemented.
Belém is the capital of the federal state of Para, has a population of approximately 1.4 million and is situated at the mouth of the Amazon. The region has a tropical climate. The rainy season starts in January and lasts until May. It generally rains several times each day in several short but heavy cloudbursts, which can quickly cause flooding. Average annual rainfall is 2,897 millimetres, while the average temperature throughout the year is 26°C with no great fluctuations between the months. However, the temperature differences between day and night are more noticeable. During the day the temperature can quickly rise to 38°C and more. In combination with the high humidity this can be quite a stress for the body. And, naturally, this affects how work is carried out.
On the outskirts of the city, directly on the banks of a branch of the Amazon, is a large tank farm where various oil companies have erected tanks to supply their customers. When site investigations were carried out on the order of the authorities, contaminated areas were discovered and these now have to be remediated. Some of the contaminated soil is sandy, but very silty zones are also affected. Below are some of the key figures:
* Contaminated volume, more than 60,000 cubic metres
* Contamination by crude oil (mainly) * Average content: 15,000 mg hydrocarbons per kilogram
* Maximum levels: 50,000 mg hydrocarbons per kilogram
* Remediation target: 5,000 mg hydrocarbons per kilogram
* Utilisation: reuse at the site
The biological on-site heap technique, 'Terraferm' was chosen to remediate the soil. This degrades the mobile fractions of the crude oil and leaves the immobile long-chain fractions intact. This allows the material to be used safely at the site when the process is completed. Remediation work started in April 2005 and is still ongoing. It should be completed by autumn this year (2009).
The remediation crew is fully integrated into the tank farm's occupational safety regulations. The most important points are listed below.
+ Continuous wearing of personal protective equipment:
* Safety shoes or boots
* Hard hat * Ear protection
* Protective goggles
* Tight-fitting, long-sleeved, flame-resistant clothing
* Additional sun protection on the hard hat
* A safety harness must be worn when employees work above 2 metres
* Operation of an LEL (Lower Explosive Limit) warning device
+ There are many monitoring measures in place to ensure that the regulations are complied with:
* Work is monitored by a full-time safety officer from the company carrying out the work
* The customer's experts also ensure that the clothing regulations and safety regulations are complied with
* Daily safety briefings
* Weekly safety meetings with all blue-collar and white-collar employees at the site
* Gymnastics twice per week
+ Many formal guidelines also have to be complied with:
* Before starting work on the site every employee must be registered with the customer. They require work certificates, good-conduct certificates, health checks, wage and insurance slips.
* The customer does not allow people who have been in trouble with the police to work at the site, even if the crimes were committed in the distant past.
* The customer issues work permits each day.
The list shows that the requirements are absolutely stringent. The customers ensure that the guidelines are complied with and are quite prepared to take rigorous action in case of infringements. This includes shutting down the entire site if a rule is disregarded by refusing to issue work permits, sending individual workers off the site, triggering a penalty for breach of contract or retaining contract fulfilment bonds.
The actual soil remediation is carried out in several steps. The contaminated soil is excavated and heaped. In this system the soil is loosened and structuring material is mixed in with a "mole" that is fed by means of a wheel loader. The material goes from there to the treatment heaps, where the natural soil bacteria degrade the contaminants. Because of the soil's naturally high temperature of more than 28°C the bio-processes take place rapidly, which allows the remediation target to be reached in just a few weeks. The remediated material is then returned to a different area of the tank farm.
Authors: Dr. Thomas Caro and Dr. Thomas Berger, Zech-Umwelt GmbH, Bremen (Germany)
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