Remediation

DEKONTA Poland offers remediation of soil and water environment using the biotechnological method EX SITU and IN SITU with the use of bacteria spreading pollution.

Our scope of work:

Remediation ex-situ:

• Soil reclamation
• Professional supervision over the work
• Transport in accordance with the obtained decisions
• Neutralization and recovery of contaminated soil on remeidation plate

Remediation ex-situ onsite:

• Design and execution of bioremediation plates
• Bioremediation of land
• Supervision of the purification process

Remediation in-situ:

• Two-phase systems
• Bioremediation of soil and water
• Mechanical and chemical aeration
• Pumping and purifying water
• Container installation of waste water treatment plants

Before we start the remediation work, a proper decision must be made to allow remediation work. The decision is made by the Regional Director for Environmental Protection.

Remediation – Ground pollutions biodegradation by “EX-SITU” technology – outside the contaminated zone

The “EX-SITU” technology is suitable for shallow and accessible contaminations when ground digging is feasible economically and technologically. This technology consist in depositing the contaminated ground over specially prepared biofield and proceeding there the biodegradation process. The “EX-SITU” technological system consists of:

• biofield,
• drained water tank,
• inoculum preparation unit,
• bioreactor,
• sprinkling system.

P – bed
Pr – biofield
G – contaminated ground
Np – inoculum preparation unit
B – bioreactor
Sz – sprinkling system
Zo – drained water tank

Example of biofield construction:
Pp – sand bed (10-15 cm)
Gm – geomembrane
Pż – sand-gravel mix (10-15 cm)
M – straw mat
D – draining system

The biofield is an area isolated from bed where the contaminated ground is distributed evenly. The insulation consists of e.g. concrete with protective coating or sand bed with geomembrane. The biofield construction depends how long the biofield is intended to work. Another the biofield element is a draining system carrying away water from the biofield.

Drained water tank collects wastewater from the draining system which later is reused in bioreactor. In inoculum preparation unit a bacterial concentrate is produced what is a parent substance to biologicals produced in the bioreactor. The bioreactor produces biologicals in the quantity needed to proceed application. From the bioreactor to the biofield biologicals are delivered by sprinkling system.

In some cases the reclamation system is modified by adding ground venting system which is used i.a. for ground layer thickness 1,5-2,0 m because the whole ground volume must be aerated. For ground layer thickness 0,50-0,70 m mechanical treatment is sufficient.

The ground purification process requires not only appropriate bacteria strains but also mineral ingredients, nutrients requisite for bacteria life and water. Mineral ingredients consist of nitrogen, phosphorus, potassium (from NPK fertilizers) and nutrients consist of some food industry by-products e.g. molasses. Water used in the reclamation process is most often pumped in the contaminated zone what saves the unpolluted water. Moreover water works in nearly closed cycle (water loss due to evaporation from the biofield is unavoidable). Ground purification process is continuously monitored by chemical and microbiological analyses of ground and water samples. The analyses results form the basis for decision making referring to reclamation process continuing and its final completion.

Remediation  – Ground pollution biodegradation by “IN-SITU” technology – within the contaminated zone

Oil derived substances pollution may have relatively wide range and be present at significant depths, especially if the groundwater table is at deep level. In such cases ground replacement would be extremely expensive or nearly unrealizable due to economical and technological reasons. Therefore the best solution is the reclamation within the contaminated zone “IN-SITU”.

The technology “IN-SITU” consist in installing technological system which forces water circulation in the polluted ground and water environment and applying biologicals to the system. Water circulating in ground supplies active biologicals to the contaminated zone, where the biodegradation process proceeds. The “IN-SITU” technological system consists of:

• pumping wells that at same time serve as a hydrogeological barrier (the quantity of wells depends on local hydrogeological conditions and contamination character)
• water purifying system
• inoculum preparation unit
• bioreactor
• application system that may be a network of applying wells, sprinklers or absorption trenches and pits (the system selection depends on local geological conditions)

W – water purifying system
Np – inoculum preparation unit
B – bioreactor
A – applying wells
E – pumping wells
z.w.g. – groundwater table

Water from pumping wells flows to the water purifying system where preliminary water purification proceeds and then goes to inoculum preparation unit and bioreactor. In the inoculum preparation unit bacterial concentrate is produced what is a parent substance to biologicals produced in the bioreactor. The bioreactor produces biologicals in the quantity needed to proceed application. Biologicals are delivered from the bioreactor to contaminated zone by application system. Then bacteria strains cooperation cause decomposition of hydrocarbons in ground.

In order to keep the ground purification process effective mineral ingredients and nutrients must be added in stages of producing bacterial concentrate in the inoculum preparation unit and biologicals in the bioreactor. Other important factors are: oxygen access to ground, surroundings temperature and moisture. Therefore sometimes additional ground venting via e.g. applying wells or watering via e.g. sprinkling is applied.
Ground purification process is continuously monitored by chemical and microbiological analyses of ground and water samples. The analyses results form the basis for decision making referring to reclamation process continuing and its final completion.

Ground purification by “IN-SITU” biotechnological methods is a long-term process. It depends on local conditions but often requires from 2 to 10 years to complete.

Remediation  – Free floating product removal

Many of commonly used oil derived substances such as fuels (petrols, diesel oil) are non-polar compounds and lower in density then water, therefore reaching water level they form a floating layer of free product. Before the biotechnological reclamation starts the layer of oil derived substances floating on water table should be removed in order to enable applying and improve the efficiency of biotechnological methods.

Free floating product is removed by pumping system consisted of wells equipped with skimmers that allow to pump separately water and oil product. The system, that DEKONTA Polska Sp. z o.o. offers, guarantee air-tight process and pneumatic product transport what makes it safe and suitable for explosion danger zones, e.g. within fuel stores or refineries.

The presented system allow to pump free floating product from the depth of up to 45 m, transport the product up to 250 m from well, operate pumping process automatically, detect phase separation ‘oil product – water’ and groundwater table level changes, what enables to pump separately oil product and water. The whole system is controlled electronically.

There are two system modifications: dynamic system for free floating product removal of thickness greater than 5 cm and static system for product thickness up to 5 cm. Both modifications can be used alternatively depending on the requirements.

The pumped oil product may be reused in refineries to produce fuels or processed in other way when their quality is poor.

Reclamation – Water purification from oil derived substances

In the zones contaminated by oil derived substances not only ground is polluted but also groundwater.

Contaminated groundwater is pumped to purification system which consists of i.a. hydrocarbons separator and stripping tower. In the hydrocarbons separator the residue of free floating product, aerosols and particulate solids are separated from water and then in the stripping tower volatile organic compounds concentration is reduced. Further water purification may be continued by applying biologicals and as it is in case of grounds, oil derived substances are decomposed.

DEKONTA Polska Sp. z o.o. has at its disposal own water purification system closed in a mobile standard container which enables decreasing concentration of oil derived substances pollutions in water. It may work on its own or as a system supporting ground reclamation by biotechnological methods. The system may work in a continuous mode with a rate of delivery 3,6 m3/h and allows lowering the concentration of substances extractable by petroleum benzine to the level of 10 mg/dm3. Moreover it lowers also the concentration of iron and manganese.

The water purification system consists of i.a. hydrocarbons separator, stripping tower and iron / manganese remover.

1 – hydrocarbons separator
2 – iron / manganese remover
3 – stripping tower
4 – stripping tower air filtering system
A – contaminated water inlet
B – air inlet
C – purified water outlet
D – filtered air outlet

In many cases water purification is related with ground reclamation by biotechnological “IN-SITU” method. In this method water circulates in the process being a medium for bacteria applied to ground. Then ground and water are purified simultaneously.

Eliminating the effects of communication failures – remediation