Simpler mining water treatment

Together with Montana, GeoChemTec has the honour and pleasure to continue the Baccu Locci project of simpler mining water treatment with geochemical technology and minerals.

In a presentation, 'Simpler mining water treatment with geochemical technology and minerals' , we show case studies elucidating the application of passive treatment of heavy-metal contaminated mining water, from abandoned historic mines in Mediterranean countries. The water with metal concentrations up to a gram per litre of the remediated mining waste site of Baccu Locci was successfully treated down to less than a milligram per litre, by gravitational flow through compact filters with very reactive porous mineral granules, as developed by GeoChemTec. The technology of preparation of materials and the operation and maintenance of the filters is straight forward and can be managed by local contractors in remote mountainous areas without power, industrial equipment and constant supervision.

The lecture was presented at Remtech Europe 2021. Please, feel free to download the slideshow for further details

Accidents will happen: Insured

Severe environmental pollution by heavy metals can be extremely costly to remediate and insure if it concerns very large-scale and long-term operations. A famous example is cadmium pollution of the Toyama Prefecture (Japan) by mining, causing Itai-Itai disease with softening of bones and kidney failure, taking a century of environmental remediation since 1912. Another example is mercury poisoning discovered in 1956 in Kumamoto Prefecture (Japan), causing the Minamata disease affecting the nervous system, leading to insanity (as from 'mad as a hatter' like the hat making Mancunians working with mercury. Large-scale cleanup and settlement for damages of nearly $100 million only reached completion almost half a century later in 2010. Finally, there is the famous case of the more than 10 years of severe Hinkley groundwater contamination between 1952 and 1965, with genotoxic-carcinogenic chromate, leading to a class action lawsuit (starring Julia Roberts as Erin Brockovich) that was only settled in 1996 for a staggering $333 million.

At RemTech 2020 conference, Duncan Spencer shows what role insurance can play in managing pollution liabilities during remediation projects, inherited, or created during works. It is argued that liability insurance covering risk of larger damages in the order of $100 million is not that readily available, has maximum terms of 5 to 15 years and demands best available remediation strategy, guaranteeing maximum control over spreading of toxic substances, when immobilized on site or disposed elsewhere.

From a geochemical technology point of view, long-term isolation of pollutants in disposal sites in the dynamic natural environment of the geochemical cycle is impossible and not desirable. Since disposal sites cannot remain completely sealed forever, the controlled leakage of toxic compounds is a preferable solution, needed to slowly defuse a potential environmental bomb. Dilution is a solution to pollution if concentrations in the bio-available phase can remain below safe natural background values.

For truly stable methods of immobilization of most toxic pollutants, such as radioactive compounds now temporarily stored above or possibly definitely in deep clay deposits below ground, nature offers minerals and concretions as examples of alternatives. Take for instance concretions of quartz, composed of the most stable mineral at earth surface conditions and able to encapsulate heavy metals. Not only were they our best friend during the stone age, making for the toughest tools of flint, but further understanding of the way they form, might provide us with efficient geochemical technology to spontaneously attract, concentrate and maintain immobilized, the most dangerous pollutants, even within the dynamic environment at the earth surface and also on the very long-term.

Ashes to ashes: Coal slag

Since the first use of railway steam locomotives (1804, Richard Trevithick) and the burning of coal for electricity generation, great amounts of coal slag and fly ash are produced causing environmental problems requiring recycling and remediation.

At RemTech 2020 conference, Ugo Bacchiega presented a detailed study of a large historic coal slag waste deposit along the Ferrara railway station in the Italian Alps. Soil drillings, monitoring wells, trench, geophysical surveys, and chemical analysis show the size and composition of a body of soil, ground water and waste, contaminated by heavy metals and hydrocarbons. It was decided to leave the contaminated materials on site, keeping them in permanent security ('messa in sicurezza permanente'), by containment with a constructed green wall of vegetated, re-enforced earth.

From a geochemical technology point of view, this coal slag is only a waste when it is stored too far away from the site where it becomes a valuable commodity. It is our task to imagine application that is efficient enough to overcome transport costs, as the coal slag is an alkaline mineral reagent, required for doing work in an acid environment.

With nature as an example, we look at orebodies and think of self-sealing layers and the concentration of heavy metals herein for secondary mining. Coal slag or fly ash with hydrocarbon substrate for bacteria, when properly combined with metal sulfide mining waste, allows for recycling of metals and sequestering of carbon dioxide and mitigating climate change.

Blowing in the wind: Asbestos

The asbestos chrysotile, is a fibrous magnesium silicate mineral of which airborne dust-sized particles can be carcinogenic. This heat resistant and chemically inert mineral has been abundantly used in construction before it was banned about 20 years ago in Europe. How can geochemical technology manage asbestos pollution?

When asbestos containing constructions are damaged, special cautionary measures are required to prevent the spreading of asbestos dust. The challenges posed by exceptionally large constructions and the way these can be met with sophisticated technology were discussed by Mariangela Venco (ENI Rewind) in her lecture titled Design of asbestos removal from large-scale industrial site asset, presented at the RemTech Europe 2020 conference.

How collected asbestos is best handled and what treatment technologies are needed remains to be seen.

Can it be buried safely on the long term in special disposal sites, should it then first be encapsulated and consolidated and what would be the minimum disposal costs to stimulate recycling and treatment technology?

Can asbestos be economically transformed into harmless glass by melting or into filler by ball milling at over 1000 degrees Celsius, destroying the fibrous crystal structure?

How can we handle the voluminous and impure asbestos, diluted by building waste, soil or water?

What role can geochemical technology play in designing safe, cost-efficient and effective storage in acidic soil with natural weathering that is supported by fungi, mitigating climate change, when released magnesium ions sequester carbon dioxide?

Going with the geochemical cycle

Together with Montana, GeoChemTec had the honor and pleasure to give a presentation on geochemical technology with minerals at Remtech Europe 2020

In our presentation, 'Going with the geochemical cycle', we show various case studies elucidating the application of geochemical technology with minerals for the treatment of heavy-metal contaminated water, rock and soil, from abandoned historic mines in Mediterranean countries.

Remtech Europe is part of RemTech Expo, the most important Italian event on remediation technologies with European Commission’s Joint Research Centre (JRC) as part of the scientific committee. The internationally oriented conference enables sharing of knowledge, new ideas and elucidating case histories, encouraging the development of remediation processes and application of innovative sustainable technologies, bringing suppliers of available services and technologies together with owners of environmental problems, providing a platform for discussion between various stakeholders.

Please, feel free to download the slideshow for further details

Color Our Reef ALive

Corals are most elegant bio-geochemical engineers, building their colorful homes out of sunlight and air. But why do they bleach when stressed and how can we help them relax?

Modern, shallow (sub) tropical reefs are made by hermatypic stony ‘scleractinian’ corals. They are colonies of polyps with stingy tentacles, like the related sea anemone, secreting calcium carbonate cups; the corallite, an exoskeleton in which they can retract.

Hermatypic corals are colored by pigmented unicellular algae that they host in their tissue at concentrations of several million per square centimeter. These algae are dinoflagellates known as zooxanthellae which photosynthesize, using sunlight and carbon dioxide to produce oxygen and organic compounds, which they share with corals in exchange for nutrients and protection.

When corals are stressed, for example by extreme water temperature, salinity and light, they may expel their colored zooxanthellae and turn white (Coles & Jokiel, 1978). As the corals bleach, they become brittle and more prone to disease. When conditions return to normal, corals may incorporate the zooxanthellae again and regenerate after a while (Buddemeier & Fautin, 1993). The extreme circumstances may change the zooxanthellae from beneficial symbionts into harmful parasites that need to be expelled and if, for instance by climate change, such conditions occur too often, without time for regeneration, coral bleaching becomes permanent and entire reefs will die (Baker et al., 2018).

Coral reefs are the most diverse ecosystems on earth. They are not only a wonderful underwater world of great beauty, but they protect vast stretches of coast against wave erosion and ultimately feed billions of people with hundreds of billions of dollars’ worth of seafood. Coral reefs deserve protection and we have to:

  • Learn how to diminish environmental stress for coral reefs
  • Teach corals how to deal better with their environmental stress

We ask ourselves, for improving the well-being of coral hosts and their symbiotic guests, what bio-geochemical technology is best to use?

String of microbially precipitated nano crystals of magnetic iron oxides within the elongated cell of a magnetotactic bacteria

What is going on between minerals, metals and microbes in bio-geochemical technology?

By using minerals in bio-geochemical technology, we can influence the interaction between microbes and metals, to improve environmental management.

The health of soil and water can be managed through the interaction between microbes and metals, using minerals in bio-geochemical technology. Microbes (bacteria, fungi and algae) influence metal concentrations when deteriorating rock and minerals during bio-weathering and when forming, directly or indirectly, minerals during bio-mineralization (Gadd, 2010).

This interaction between minerals, microbes and metals determines the availability of life sustaining resources and life-threatening toxins that regulate the natural habitat of the critical zone or biosphere; the near-surface environment of rock, soil, water and air, home to living organisms.

Microbes concentrate the essential nutrients from mineral surfaces (Vaughan et al, 2002); i.e. carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur that form 95% of the biomass and other elements with essential biochemical and structural functions such as K, Ca, Mg, B, Cl, Fe, Mn, Zn, Cu, Mo, Ni, Co, Se, Na and Si. Microbes and minerals also control the concentrations and bio-availability of thirteen trace metals and metalloids that are considered priority pollutants i.e. Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl and Zn (Sparks, 2005).

Many examples show how microbes interacting with metals may operate in environmental management. For instance, microbial metal mobilization through bio-leaching can be used for metal recovery, recycling and bioremediation of mineral waste and contaminated soil (White et al, 1998). Microbes can be used to immobilize metals by bio-precipitation, for decrease of toxic concentration in bio-available phases. Reduced metal(loid)s like Se(0), Cr(III), Tc(IV) and U(IV) form insoluble precipitates through reduction in anaerobic processes. Single-oxidation-state metals are immobilized during precipitation with biologically produced sulfide and phosphate. Immobilization through microbial biosorption occurs by physico-chemical binding of metals on dead and living walls of microscopically small cells that expose a very high surface per weight to the metal containing solution. Biominerals such as microbial nano crystals of magnetic iron oxides precipitated by magnetotactic bacteria can be used for sorption of metals and their recovery from solution by magnetic separation.

For practical use of microbes and minerals in environmental management we have to ask: How can microbes manage metals better with minerals in biogeochemical technology?

featured image of geochemical phytoremediation technology showing burning roses and ash modified after an image of arsthanea.com

Can phyto-geochemical technology promise a rose garden?

By controlling the mobility of nutrients and contaminants, using phyto-geochemical technology, we can support plants in growing in polluted environments.

We like to know what role phyto-geochemical technology can play in growing plants on strongly contaminated soil, not necessarily promising a rose garden, but at least improving success and efficiency of phytoremediation.

Phytoremediation uses higher plants to remove, immobilize or degrade contaminants such as metal(loid)s in soil and water and two approaches can be distinguished (Bolan et al., 2011):

  • Phytoextraction aims at cleaning soil and water by the uptake of contaminants and their storage in plant tissue. The contaminants are removed by harvesting the plants.
  • Phytostabilization aims at immobilizing contaminants by roots and plant cover, preventing their percolation to groundwater and their spreading by wind and water erosion.

Nutrients and contaminants enter the plants via the rhizosphere, a volume of soil or water that envelopes the roots in a few millimeters thin layer. Their mobility and uptake depend on the composition of soil and the activities of the plant and associated microbes (mycorrhizal fungi and bacteria) in the rhizosphere.

The mobility and availability of, for instance, metal(loid)s is strongly regulated by the pH of the pore water of the soil. The plant influences the pH by releasing fluxes of H+ or OH-, counterbalancing the uptake of cations and anions, respectively (Tang and Rengel 2003).

The mobility and availability of metal(loid)s is also defined by the charge of soil particles with a high surface per weight ratio. Fine-grained organic matter and clay minerals show strong capacity for adsorption and exchange of cations or anions, expressed in the Cation- and Anion Exchange Capacities (CEC and AEC) of the soil (Bolan et al., 1999).

Plants have trouble distinguishing between useful nutrients (e.g. K+, Ca2+, PO43-) and hazardous contaminants (e.g. Tl+, Cd2+, AsO43-) of the same charge and similar size (Reid and Hayes, 2003).

With phyto-geochemical technology we aim at supporting plants growing on contaminated soil by influencing the pH, CEC, AEC and bio-availability of nutrients and contaminants, using inorganic amendments (e.g. liming materials, phosphate compounds and clay materials) and organic amendments (e.g. topsoil, compost, manure, waste water treatment biosolids, peat and biochar).

We like to know: What amendments are required for effective phyto-geochemical technology and; How to administer amendments for efficient phyto-geochemical technology?

featured image of geochemical technology validation showing the canaries Fokke and Sukke in laboratory coats besides a steaming retort and Fokke asking: very impressive colleague, but does it also work in theory?

Works geochemical technology validation also in theory?

We can predict performance and validate geochemical technology before application and testing in the natural environment on large scale and long term.

When we apply geochemical technology on the small scale and short term, we can readily monitor its performance and establish to what extend the prediction of its working is correct. The theory of a geochemical process is tested by putting it into practice. Geochemical technology validation is immediate and straight forward

When designing geochemical technology for application on a larger scale and longer term, then the testability of the theory decreases. Simultaneously, the consequences of eventual malfunctioning become more serious and therefore the prediction of the course of events needs to be more accurate.

Since we can no longer readily prove the working of geochemical technology in practice, we need to ask ourselves, can we prove the working of geochemical technology in theory? How can we assure a priori geochemical technology validation? Such are not trivial questions and are subject of vigorous discussions on model validation in science and engineering of, for instance, the long-term stability of disposal sites for hazardous (radioactive) waste (Nordstrom, 2012). If we think we can indeed forecast results of geochemical technology, then what instruments are available for predicting the future most accurately?

We can distinguish four ways for obtaining high-quality geochemical technology and for improving the prediction of its working within the natural environment.

  1. Nature provides examples. By analyzing samples and explaining the distribution of measurements, we gain understanding of past and ongoing geochemical processes. This understanding is tested each time we study present processes and the way they leave traces in the fossil record. The past is the key to the present and the future.
  2. Laboratory- and pilot field tests provide another way to test our understanding of geochemical technology. Of course, only to a certain degree, because transposing technology to a different scale and into the natural environment, increases uncertainty as the effect of unknowable influences also increases.
  3. Conceptual- and scientific models provide the means to discuss our understanding of the working of geochemical technology and to put it to logical tests. Models should be elegant and simple, reflecting their limitations as an idealized representation of a complex reality and facilitating communication with a broad and critical audience.
  4. Finally, geochemical technology should be designed and applied in such a way that it automatically attains stable- or neutral equilibrium, so that it never evolves to an unpredictable unstable state.

For discussing the theory of geochemical technology in further detail, we might ask ourselves: What models most elegantly represent geochemical technology?

logo of GeoChemTec within circle of two light blue arrows

What is geochemical technology?

When using geochemical processes to improve the environment, we apply geochemical technology and perform geochemical engineering.

Schuiling (1990) defines geochemical engineering and presents an example of a very early application of geochemical technology. He writes: “If we adopt the definition that geochemical engineering is ‘the use of geochemical processes to improve the environment’, then it can be said that Hannibal practiced geochemical engineering when he poured acetic acid over limestones to secure a passageway for his elephants across the Alps (LIVIUS)”.

Geochemical technology arises from combining principles of the science of geochemistry with the practice of environmental engineering. While geochemists study the chemistry of the earth and the geochemical processes that define the distribution of minerals and chemical elements in rock, water and air; geochemical engineers apply this understanding of geochemical processes in the engineering of the natural environment.

Geochemical technology typically:

  • Fits within the course of geochemical processes and goes with the geochemical cycle;
  • Uses mineral reagents to control chemical elements in configurations that stay stable on the long term;
  • Aims at solutions for environmental problems that blend better into the natural environment and;
  • Provides innovative tools for environmental management that help to better conserve, control and protect precious natural resources.

What are examples of geochemical technology? .