Iron-Carbon Micro-Electrolysis Filler

Iron-carbon micro-electrolysis filler is a wastewater medium that uses a bit of built-in electrochemistry to destroy pollutants that biology cannot. Each pellet contains iron and carbon pressed together with a catalyst. The trick is what happens when two different conductors, here iron and carbon, touch each other while sitting in a conductive liquid like wastewater: they form a galvanic cell, a tiny battery, with the iron as the negative pole and the carbon as the positive. A pellet packed with iron and carbon grains is riddled with countless such micro-cells, and each drives a small current through the water on its own, with no plug or power supply. Those currents power chemistry. The iron gives up electrons and dissolves, reducing some pollutants directly; the fresh iron ions and the reactions at the carbon generate hydroxyl radicals, an extremely aggressive oxidant that rips apart complex organic molecules. Between the reduction and the oxidation, refractory compounds, the ones that pass straight through a normal biological plant, are broken into smaller, simpler pieces. Pack a tank with the media, run the wastewater through, and it comes out with its hardest pollutants already cracked open.

Three things, mainly. First, it cuts COD, the measure of oxidisable pollution, typically by 60 to 85 percent on the difficult industrial wastewaters it is used for, because the micro-electrolysis oxidises and breaks down the organic load. Second, and often the real point, it makes the water far more biodegradable. Many industrial effluents are toxic or simply indigestible to the bacteria in a biological plant; by cracking the big, refractory molecules into smaller ones, the iron-carbon step raises the B/C ratio, the share of the pollution that bacteria can eat, by a few tenths, turning an untreatable stream into one a normal biological stage can finish. Third, it decolourises and removes some heavy metals: the iron released forms a coagulant that pulls dye colour and metal ions out of the water. All of this happens without electricity, drawing only on the galvanic energy of the iron and carbon, so it uses much less energy than a powered electrochemical system. Tell us your wastewater and its COD and we will estimate the treatment.

It sits near the front of the treatment train, as a pretreatment or advanced-oxidation step, ahead of the biological stage. The wastewaters it is built for are the awkward ones: high-strength, refractory or toxic organic effluents from dye and printing works, electroplating, chemical and pharmaceutical manufacturing, and similar industries, where the pollutants are too concentrated or too resistant for biology to handle directly. The iron-carbon reactor goes first and does the hard chemical work, knocking down the COD and breaking the refractory molecules, and its outflow, now much more biodegradable, passes on to a conventional biological plant that finishes the job cheaply. Often the water is acidified slightly going in, and the iron released is settled out afterwards. Used this way, the filler is the key that makes an otherwise impossible wastewater treatable, and it is a common retrofit ahead of biological systems that are struggling with a difficult influent. Send us your process and effluent and we will advise where it fits.

Each pellet is a pressed and fired blend of refined iron powder and fine carbon, in the form of coke, together with a metal catalyst, at least 5 percent, and an activating agent, all of which sharpen and sustain the micro-electrolysis. The catalyst is important: it keeps the iron and carbon reacting and stops the bed from passivating and going dead, which is the main failure of plain iron-carbon mixtures. The pellets are elliptical and come in a range of sizes, from about 3 up to 18 millimetres, chosen for the reactor and the flow. They are dense, around one to one and a half grams per cubic centimetre, and strong, holding a compressive strength of at least 3 megapascals with a breakage rate under 3 percent, so the bed does not crumble in service; and the packed bed leaves about 65 percent free space for the water to flow. The media are consumed slowly as the iron is used up, so they are topped up over time. Send us your reactor size and flow and we will specify the grade and the quantity.