Reducing energy and cutting emissions

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The tank cleaning sector in Europe cannot escape from more stringent environmental legislation that has become law.
This will have an impact on tank cleaning businesses as well, as new legislation aims to meet net-zero targets set for 2040 and then 2050.
Therefore, EFTCO is keen to warn its members that the sector must look into how these new targets can be met swiftly.
It is obvious that this will not be an easy task, said Erwig Seliaerts, the president of EFTCO.

Raising concerns

The individual national organisations that are part of the EFTCO family have been aware of this issue for some time.
The organisation’s members have been supporting different studies carried out by universities and/or colleges investigating a range of sustainability topics:
• Is there a solution to the removal of “eternal chemicals” like, for example, per- and polyfluoroalkyl (PFAS)?
• How can improvements be made at the various wastewater purification plants?
• How can tank cleaning firms reduce CO2 emissions?
• Where is heat recovery possible?
• How can water be saved?
• Can organisations get rid of paper cleaning documents?
The removal of PFAS is an important topic in Belgium at the moment and analysis carried out by the Belgian national organisation CTC indicated that in some regions these chemicals are present in the water they have been using.
This is even the case in potable water as well as in groundwater used.
The amount discovered is far below the legal limits, but work is being carried out in an attempt to remove them completely.
This can be done with activated carbon technology, but some suppliers refuse to accept the used carbon for regeneration when perfluor components are present and this make this method too expensive. More work is being done into how this issue can be resolved.
One of the supported studies has proven that the settling process in a biological treatment can be improved when granular sludge is created.
The study indicated the way in which this granular sludge can be achieved in practice. As settling is often a problem in the sector, additional purification steps like an effluent flotation or a sand filter are often necessary.
These additional technologies can be avoided with granular sludge. This additionally offers the benefit of reducing sludge production by up to 25%, lowering energy requirements for aeration by up to 30%, and enhancing filtration, thereby reducing the necessity for additional chemicals.
To increase tank cleaning companies’ awareness of their CO2 emissions, the SQAS questionnaires have introduced several questions about the calculation of their carbon output and it has highlighted targets to get these levels reduced. As tank cleaning cannot function efficiently without using a lot of hot water, commonly heated with natural gas or gasoil, the reduction of these emissions is not straightforward.

Energy reduction

There is the possibility of using electricity for the heating process, but this has proved to be too expensive at the moment.
Other energy sources like hydrogen could be a possibility in the future, but currently no solutions are readily available on the market.
Further optimisation of the cleaning procedures reducing the (hot) water per cleaning cycle and to enhance heat recovery are more achievable at the moment.
The recent spike in energy prices has, inadvertently, prompted more work into how this heat can be recovered.
This not only pertains to cost control, but it also carries significant implications for reducing carbon emissions. Heat recovery can be facilitated by capturing and utilising condensate from steam production.
Heating loaded tanks in this manner was not commonplace due to concerns over potential contamination of condensate within the tank's steam boxes, especially when the tank had been heated using a water/glycol mixture in the past.
The wastewater from tank cleaning holds a substantial amount of heat. The most significant recovery potential lies as the water exits the tank. However, the presence of product residue in this water complicates matters, as it quickly contaminates heat exchangers.
Technology exists for recovering heat from wastewater treatment effluent, circumventing the pollution issues present in tank cleaning wastewater. However, the current return on investment remains modest, particularly when energy rates are stable or not rising.
However, by saving 5°C during the water heating process for cleaning, and considering 10,000 cleanings annually with a water consumption of 1.5 m³ per cleaning, it is possible to avoid emitting 33,620 kg of CO2. Moreover, this figure is likely to be even higher in practice, as it does not factor in the burner efficiency. In reality, the theoretical calculation may underestimate the natural gas requirement, resulting in increased emissions.
Tank cleaning stations must prioritise water reuse due to the increasing scarcity of fresh water resources. As a result, authorities are establishing targets to curtail industrial water usage.
Therefore, it is imperative for tank cleaning stations to strategise methods for water conservation and reuse to align with these regulations and contribute to sustainable water management practices.
The initial installations were constructed with ultrafiltration as the primary step, succeeded by a reverse osmosis system following physico-chemical and biological treatment stages.
Notably, the bio sludge from the biological treatment is eliminated by the ultrafiltration unit, eliminating the need for a settling tank post continuous biology or a settling step in a sequenced Batch reactor. Additionally, the reverse osmosis process effectively eliminates any remaining colour and taste residues that may persist after ultrafiltration.
The primary challenge arises from the creation of not only reusable water, but also a concentrated waste stream, necessitating a resolution.
As this concentrate harbours the same pollutants typically discharged in the absence of water recovery, authorities increasingly consider permitting its discharge into sewer systems linked with municipal wastewater plants or even into surface water, provided it meets acceptable quality standards.
An added benefit of this installation is the recovery of residual heat from the wastewater alongside the water itself.
The reclaimed water can be up to 15°C warmer compared to the fresh water intake. As demonstrated in the preceding section, this heat recovery significantly mitigates CO2 emissions, highlighting the multifaceted advantages of the system.
Effluents in the different purification steps during tank cleaning:
The recovered water at the end of the process is devoid of minerals, rendering it soft and suitable for use as feedwater in steam boilers.
Consequently, the need for ion exchange softening is eliminated, thus circumventing the production of brine typically used for ion exchange column regeneration.
Furthermore, by incorporating a disinfection agent, this water can be safely utilised in the food industry without any concerns. However, while suitable for industrial applications, it is not recommended for drinking due to its mineral deficiency.
The initial experiences suggest that installations of this nature can yield the following outcomes:
1. 70% of the water can be recuperated;
2. Rainwater can be treated, thus reducing the need for more fresh water;
3. The quality of the recovered water is perfect as feeding water for steam boilers and so avoids a lot of brine;
4. The heat recovery of 15°C on 70% of the water used will reduce the CO2 emissions of a single cleaning operation by 6.75 kg. For 10,000 operations annually, this will lead to a reduction of 67,240 kg.

Of course, the operating costs of such an installation is not small. The additional costs are estimated to be around €0.6/m³. These costs include chemicals, electricity use and the membrane costs.
In Belgium, the payback period for such installations is approximately 3.4 years when no subsidies are factored in. However, after subtracting Belgian subsidies, this payback period is reduced to 2.84 years.
Despite the current high investment costs, the future trajectory suggests an increase in fresh water rates.
Additionally, authorities are likely to mandate heightened environmental contributions for remaining pollutants discharged into sewer systems or surface waters.
These forthcoming developments provide companies with a compelling incentive to invest in water-saving technologies. Ultimately, this collective effort towards water conservation serves as a significant environmental benefit for all stakeholders.

Campaign initiative

Since 2018, EFTCO has been actively involved in Eclic and the electronic ECD. While the adoption of this non-commercial platform has been gradual, the organisation remains confident in its numerous advantages.
By establishing a standardised communication protocol, EFTCO aims to prevent cleaning stations from needing to interface with various other (commercial) platforms in the future, which can be both complex and costly.
The eECD 2.0 solution enables cleaning stations to operate entirely digitally.
To facilitate a smooth transition, during which some customers may still prefer paper documentation, EFTCO recognises the printout of the eECD 2.0 as a valid EFTCO Cleaning Document.
By potentially eliminating over 4 million paper ECDs generated annually, EFTCO aims to make a significant contribution towards reducing our environmental footprint.

For more information: Visit: eftco.org

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