Halfway – Cleaning with chaos

Name:  Suze-Anne Korteland (25)

Nationality: Dutch

PhD supervisor: Dr. T.J. Heimovaara

Promotor: Professor J. Bruining

Subject: Source zone remediation: enhancing of mass transfer rates

Thesis defence: In about two years

Suze-Anne Korteland (MSc) thinks deeply about how she should summarize her PhD research subject: “Soil pollution is an increasing problem. The subsurface is never completely homogeneous, as a result of which some of the contaminants stay in the pores. The goal of my research is to test an improved soil remediation method.”

To clean contaminated soil, wells are used to inject fluid into the polluted parts of the subsurface. “Often oxygen is pumped through the soil, which reacts in-situ with the pollution. Another option is to inject oxidators”, Korteland says. When pumping constantly in the same direction, the fluid always flows via the same route. The pores that are reached by the flow are cleaned, but the pores outside the flow path remain contaminated.

“My ultimate goal is to develop a remediation method whereby the fluid will reach more pores than is now often the case. This method aims to create a ‘chaos’ of alternating and varying flows, by rhythmical pumping and injecting with three or four wells, to change the flow pattern constantly”, Korteland explains, adding that, in addition to the flow path, flow velocity is also a very important aspect. “The oxygen and oxidators have to reach the polluted soil before it reacts with other available organic material.”

At the moment Korteland is designing an experiment to simulate flow through a porous medium. The set-up consists of a cylindrical tank with a diameter and height of approximately 60 centimetres, studded with electrodes, and a pumping system. The electrodes are part of an electrical resistance tomography (ERT) measuring system. With ERT, electrical current is injected into the tank, while the potential difference is measured between opposite electrode pairs placed around the tank. “The tank will be filled with sand and water when the measuring system is finished”, Korteland explains. “I’ll place a mini-well in the tank through which a saline solution is injected in the porous sand. I’m currently developing software to make fast calculations with the measured potentials, to calculate a 4D image of the fluid flow within the tank.”

Over the course of the next two years, Korteland hopes to finish the software and the ERT measurement system. “When the measurements and calculations can be trusted, and the flow pattern of an injected solution can be made visible in 4D, it will be time to simulate chaotic flow”, she says. “By alternating pumping and injecting with three or four mini-wells, the flow paths should change and more pores should be reached by the injected solution.” In a later phase of the project, Korteland’s results will be up scaled to field conditions; however, that moment, she says, is still far away: “Let’s first see if we can simulate this improved remediation method, before we think about applying it!”

De pensioenen worden bevroren tot de ‘dekkingsgraad’ van het fonds weer op orde is. “Dit heeft gevolgen voor de uitkeringen aan gepensioneerden”, schrijft het ABP in een verklaring, “maar ook voor de opgebouwde pensioenaanspraken van werknemers en ex-deelnemers.”