Published in Architect and Builder, volume 52, issue 2 March/April 2001

The Boardwalk Casino, Port Elizabeth

The builders of the Boardwalk Casino in Port Elizabeth encountered an unforeseen environmental problem when they started construction and landscaping of the car park and gardens - they struck oil; old engine oil and fuel from a service station that had occupied the site.

The situation was so bad that fumes from the blackened soil were ignited by sparks from the metal excavation tools, producing flash burns. In all, about 4,000m³ of soil was polluted and the normal practice would have been to dig it out, truck it away and then import 4,000m³ of new soil. The cost would have been R3m to R4m, involving delays and huge penalties for the contractors. But there was another way. Instead of sending in mechanical shovels and heavy trucks, Sun International called up an army of invisible bacteria to quietly digest the oil and clean up the soil.

The firm which undertook the work was DCS. They used oil-degrading bacteria supplied by a Cape Town firm, BIO-SYSTEMS SA, to do the job. The microbes were introduced to the soil through the ground water and a drainage system was developed to ensure that they spread to all the contaminated ground. The process was speeded up with pumps circulating water under pressure and partially cleaned water was run into a holding tank for more intensive treatment. Construction work continued.

The casino opened on schedule but work was still going on underground where the water and its invisible oil-fighters continued to circulate through December and January. In the third week of February, tests were carried out which showed that the ground water was free of oil products.

The cost of the whole bioremediation project was less than R1m - a quarter of the cost of replacing the polluted soil the hard way.

Industrial case history 2: bioremediation of a diesel spill in Lesotho

Green Banana Industries were awarded the contract to clean up a hydrocarbon spill at a bulk diesel storage depot in Lesotho. An accidental ‘overfill’ had resulted in some 15,000 litres escaping the bunded area (a masonry open-topped box within which a liquid storage tank is mounted). 135m³ of soil was contaminated to the extent that it actually squelched as you walked over it.

The oil distributor engaged the services of a registered consulting engineer, Chris Badenhorst, who established the exact extent of the oil plume and the percentage of contamination over the site. After consulting with BIO-SYSTEMS SA, Badenhorst and his experienced clean-up team commenced work on the site.

This is how it was done:

1. The site was cleared of extraneous material. A front-end loader skimmed the percolated, diesel-soaked soil to stockpile, mixing in 35kg of Nitrogen and Phosphorous in the process – diesel is deficient in these nutrients which are essential for the viable performance of microbial activity. The limit of penetration was reached at a depth of approximately 500mm.
2. 1kg of loose BIO-SYSTEMS B350 microbial seed and 200 litres of Spill-Sorb^TM fibre were then hand scattered, raked in as far as possible into the hard ground and then lightly watered. 
3. 150 black plastic sheets were then laid over the excavated area and material from the stockpile was spread in a 100mm layer. Once again 200 litres of Spill-Sorb^TM and this time 300g of B350 were hand broadcast over the replaced material, which was rotovated to thoroughly mix the constituents, and lightly watered. This procedure was repeated until the last layer from the stockpile was spread.
4. The entire site was then thoroughly wetted to re-hydrate the microbial powder. 
5. Finally, 400 litres of Spill-Sorb^TM was spread as a thermal cushion (the sun gets hot in Lesotho!) and the site covered with plastic sheeting, weighed down and secured by broad planks to reduce point loading and compaction to a minimum. Soil was also heaped around the edges to prevent aeolian disturbance as far as possible.
6. After five and again 10 days, the plastic was carefully opened and more water sprayed onto the layered material.
   

After six weeks an inspection was conducted, but not a great deal of difference was apparent. However, three months after the plastic sheets were laid all vestiges of oil had disappeared.

Today the soil is a healthy light loamy colour with a dry earthy aroma like the rest of its surrounding environment.

Industrial case history 3: roadside oil spill

Following a freak collision near Benoni in Southern Gauteng, a road tanker rig loaded with diesel – parked up at the time while the driver rested - discharged several hundred litres of fuel on the hard shoulder just outside the small country town  of Bapsfontein in the early hours of a frosty morning. All the protocols were obeyed; the authorities responded, the leak was stemmed, the diesel contaminated road surface and hard standing were superficially cleaned, and life went on.

But all was not well in rural paradise. A few days after the accident, a farmer adjacent to the road, noticed that there were traces of diesel in his borehole (artesian well) water used to fill the drinking troughs of his prize dairy herd. Traces became a ‘slick’ and his herd and business, were at risk. There was a severe drought at the time and water was at a premium. A crisis was brewing. Phones rang in the offices of local authorities and insurance consultants and, driven by legal practitioners, a specialist bio-remediation contractor (one of our distributors as it happens) was appointed .

What had happened? Diesel spilled from the damaged tanker had percolated into the soft soil abutting the compacted road reserve. Here it had accumulated and found its way into the network of miniscule underground water channels that underly the sub-surface in most geological strata. This had taken a week or so, but once established, the diesel drained into the ‘water table’ reservoir from which the farmer’s borehole drew. So it was only a matter of time before diesel was mixed with the water and pumped up to the drinking tanks. 

The clean up

The contractor did three things simultaneously:

1. Formed a crude ‘separator’ between the pump discharge and the drinking trough to provide the cattle with ‘cleaned’ water to drink.
2. Lowered 2m long x 60mm diameter Spill-Sorb^TM ‘mini-booms’ (like long sausages) on polypropylene ropes into the borehole riser casing to absorb diesel from the below-ground surface of the well. Each boom was allowed to ‘soak’ for five minutes then withdrawn for observation. As the contamination decreased, residence time was increased.
3. Where the soft soil commenced at the spill site, Spill-Sorb^TM fibre was mixed with BIO-SYSTEMS B350 and fertilizer (namely Nitrogen and Phosphorous). The treated area (25m x 10m) was then watered thoroughly and covered with plastic sheeting to prevent desiccation from the daily hot sun.
   

The Spill-Sorb^TM booms were highly successful in controlling the contamination because, after soaking up the initial pounding of diesel, they absorbed fuel migrating into the catchment well faster than the diesel was travelling in the feed drainage channels. Spill-Sorb^TM absorbs only oil, so the now de-contaminated water was left behind for the pump to lift; with a back-up  ‘second string’ via the separator, to the cattle drinking trough.

Meanwhile the B350, initially supported by the Spill-Sorb^TM fibre ‘mother’, which gave thermal insulation and provided air passages for essential water and (atmospherically sourced) oxygen - initially from the applied irrigation - was busy degrading the fuel contaminant lodged on soil particles, and mobile in the water streams underground.

After three days, some 20 litres of Hard Surface Degreaser (HSDG) were poured down the borehole casing to encapsulate, clean and ‘drop’ any oil residues not absorbed by contact with the Spill-Sorb^TM mini-booms.

Within seven days the water was declared fit for animal consumption, and within two months, the site was cored, sampled and tested and declared ‘bioremediated’.

The final cost, although accountable was probably less than 20% of that which would have been incurred had conventional litigation taken its toll. With the onset of the rainy season, diesel fuel lodged underground in dehydrated pockets would again have been flushed out to frustrate the farmer.

Note: 1lt of diesel has the potential property of contaminating 1,000lt of water to a level where man cannot drink it without vomiting.

Industrial case history 4: transformer oil spill

A national electricity power-generating authority awarded a maintenance contract to a preferred contractor for the refurbishment of transformers on various sites across South Africa. Due to logistical problems sub-contractors were appointed by the awardee. This is accepted practice; the responsibility for competence resting with the awardee.

Due to a series of innocent circumstances, the workers commenced the routine replacement of an oil cooler on a ‘phased out’ transformer. Something went wrong and aproximately 500lt of oil coolant in the (thought-to-be-empty) sump accidentally drained out - half into the bunded area and half outside onto the surrounding ground. (The ‘bunded area’ is within the low brick wall within which the transformer is erected to ensure that any such spillage is contained.)

Transformer oil is relatively ‘thin’ and flows freely, especially when it is warm - it is used to quickly absorb and transport heat away from the coils of a transformer. The day the spill happened was a warm one so the oil rapidly dispersed into the bunding aggregate (25mm crushed granite chippings) and soaked into the ground onto which it had spilled.

Such sites must maintain a clean bill of environmental health and compliance was essential. A spill response contractor was appointed.

Spill response

This is the method the contractor used to tackle the problem:

1. Bunding aggregate
   A concrete mixer was set up on an adjoining concrete slab, on to which the bunding aggregate was tipped from manually loaded wheel barrows pushed along riaised scaffold plank walkways into  stock pipe. This initially employed four local men. A further two men charged the rotating drum of the mixer with 100kg of contaminated aggregate (20 shovels each). Into this half a litre of BIO-SYSTEMS HSDG was poured along with 25lt of unpotable water hand pumped up from a local marsh; per batch. The mixer was run for three minutes, then the ‘cleaned’ aggregate discharged to the other side. This worked well and the operation was completed in three days. The oil had been encapsulated by the HSDG and it was allowed to dry on the slab in the hot sun.
   
   The internal faces of the bund walls and the floor of the bunded area itself were first wiped over with Spill-Sorb^TM 400 x 400mm cushions to absorb any liquid transformer oil. Then cold water pressure was used to clean using a 20 percent solution of HSDG that removed the last vestiges of oil that had penetrated the interstices of the concrete (all concrete and similar ‘hard surfaces’ have myriads of minute cavities in which an oleum contaminant can lodge).
   
   Because of its encapsulating properties, the HSDG removed the oil from the pollution equation and the rinsate could be safely discarded on site (i.e. no removal or disposal costs). Given a clean bill of health, the aggregate was returned to the bund, spread and the transformer – the repairs now completed – was returned to service.
2. Hard ground external to bund
   This presented a different problem. Core sampling indicated that the plume had not penetrated deeply over most of the area, however, there had been greater contamination over the back-fill of a couple of previously excavated line trenches. Because of the presence of sub-surface wires and pipes (plotted on ‘as-built ‘ drawings, but not necessarily exactly where they were marked) mechanical excavation was ruled out. Therefore, a team of men with picks and shovels were engaged to loosen and then load and cart the contaminated soil in a barrow train. Again the concrete slab was used to spread the soil or gritty ground in a long windrow some 4m wide and heaped to 3m high for 20m. This was then treated by mixing in a blend of Spill-Sorb containing  BIO-SYSTEMS B350 at a rate of 100g / m³ + 400g /m³ of selected fertilizer.
   
   Mixing was done by a light bucket tractor, working from both sides, and the entire mixed windrow was then sheeted with plastic and left for four days. The sheeting was removed, it was turned and watered again, then sheeted for seven days. This process was repeated once a week. After five weeks the TPH (Total Petroleum Hydrocarbon count) had reduced considerably. After two months it was found to be non-existent and the ground was returned to its original position.
3. Exposed Plume Floor
   In the meantime, the insitu ground, especially in the old trench lines (referred to above), was locally treated with Spill-Sorb and B350 (‘spotting–up’ where the oil contamination was apparent). After bioremediation was certified to the desired level by the professional laboratory,  the ground was replaced and the job considered satisfactorily completed.
   

Note: As a matter of interest, under normal conditions, time and costs could have been saved by scarifying the Spill-Sorb and B350 into the contaminated surface and then laying a thin over-blanket of selected ‘material’. In this case, cables and some control valves were just beneath the surface and suitable material was not available for a considerable distance.