EU boost for wet waste treatment solution

Written by: RWW | Published:

Thanks to a European Commission-funded project, new research has begun into a new waste treatment solution. John O’Regan, CEO of SCFI, the company behind the technology at the centre of the project, explains its significance.

Supported by the EU’s LIFE+ environmental research funding programme, the Lo2x project in Valencia, Spain is the first of its kind in Europe. 

Firstly, it will provide valuable evidence of the environmental and economic benefits of using a patented super critical water oxidation (SCWO) process to treat wet waste. What’s more, the findings of the project could very well change the way we tackle increasingly contentious issues surrounding today’s wet waste disposal on an international scale.

Lo2x will see the installation of SCFI’s AquaCritox technology - which uses SCWO to destroy organic waste (e.g. sewage sludge and agri-food waste) while simultaneously generating renewable energy and recovering valuable by-products. 

At the wastewater treatment plant (WWTP) in Valencia, the prototype installation will provide live, round-the-clock analysis of the impact of SCWO on sewage sludge and other wastes - marking an important step forward for a technology that has already demonstrated its enormous potential throughout its 15-year development.

A super critical waste treatment solution

Throughout Europe and the rest of the world, plant operators like Ivem (which operates the project’s Paterna facility) are facing increasing social, political and economic pressure when it comes to the divisive issue of wet waste disposal. 

Current trends suggest that in the EU, sewage sludge alone will reach 13 million dry tonnes annually by 2020, but disposal methods, including land spreading and landfill, are prompting growing public opposition. 

Many are voicing strong concerns about the shortage of available land, the introduction of potentially harmful waste and leachates into the environment and the very real threat of disease outbreaks. 

This is reflected in political pressure, such as EU directives, and economic barriers like rising landfill taxes. 

Traditional destruction methods, for example waste incineration, have been met with similar obstacles.

With pressure mounting, extensive testing carried out by SCFI has already demonstrated the capabilities of SCWO in delivering a cost effective, sustainable and scalable treatment solution for a variety of sewage, municipal and industrial wastes. 

Following more than a decade of research, AquaCritox has been developed to provide WWTPs with a single-step solution to the treatment of wet wastes using SCWO. The Lo2x project is the next stage of this development. 

It enables a real-time demonstration of the clear financial, logistical and sustainability benefits AquaCritox offers the waste treatment sector, as well as the positive knock-on effects for related industries, such as agri-food.

The process

Using the patented SCWO process, mixed wet waste at the Lo2x testing site will be subjected to pressures of 221 bar, and temperatures of 374°C. Under these conditions, water enters a fourth ‘super critical’ phase, where it becomes neither a liquid nor a gas, but a universal solvent for gases and organic compounds - even those that are normally insoluble in water. At this reduced water density, the solubility of organics greatly improves.

AquaCritox then adds oxygen, creating a very rapid and practically complete oxidation reaction that converts 99.99% of the organic materials present in the waste stream into inert by-products. 

This destruction rate is far higher than conventional wet air oxidation or incineration and all residual materials are non-hazardous and can be safely disposed of. 

With SCWO, all inorganic materials (including phosphorus and heavy metals) are easily separated and treated in a separate step.

The AquaCritox process is safe and odourless, and does not generate any hazardous emissions or by-products. What’s more, once underway, the elevated SCWO temperature is maintained by the significant levels of heat generated by the exothermic reaction, so the whole process becomes autothermal. Additional heat can be converted into steam and hot water or renewable electricity - making AquaCritox the first technology to have a positive energy balance from processing wet waste.

Investigating SCWO

Operating 24-hours a day, the Paterna prototype will treat up to six tonnes of sewage sludge, agri-food waste, industrial wet waste and landfill leachates daily and will remain in operation until 2016. 

The project’s results will be used to identify the best processing conditions and mix ratios for treating and co-treating various wastes using SCWO. It will also investigate the efficacy of energy and resource recovery and the impact on wider operations at the plant.

At SCFI, we expect a significant reduction of the plant’s carbon footprint to be a key effect of the project. AquaCritox delivers complete wet waste destruction in one single step - eliminating the need for landfill and other environmentally sensitive disposal methods, and meaning there is no need to truck waste off site. Improving its environmental impact in this way will help the plant contribute towards important EU objectives, including waste-to-landfill targets and the European Resource Efficiency Roadmap. 

With AquaCritox, the route to disposal is fully secure, providing total control of the entire process as well as the costs involved. 

As a result, the Lo2x project is also expected to have positive economic implications for the Paterna plant. 

SCWO is far more cost effective than traditional treatment methods, with faster reaction rates, a smaller plant footprint and lower capital cost. It also allows for renewable energy generation, as well as recovery of valuable resources like phosphorus that can provide an additional revenue stream. 

Using SCWO to treat wet waste will also break any dependency on expensive dewatering and drying equipment, and avoids the large unrecoverable loss of energy used to heat or dry wastes prior to disposal.

Lo2x is a joint project between SCFI as the technology developer, and a series of Spanish delivery partners. It will be coordinated by research specialist AINIA at Ivem’s wastewater treatment plant, with delivery and engineering support from Isolux and Imecal. 

Funding from the EU LIFE+ Environment programme will be used to meet 50% of the project’s €2.9m budget.  

For more details about AquaCritox or the Lo2x project, visit www.scfi.eu

 


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