New Treatment for Wastewater

In the article “Green Iron” from The Economist, the author discusses a new solution for treating industrial wastewater. As we all know, wastewater that is dumped from factories into rivers and streams has large amounts of harmful dyes, nitrogen, phosphorus and other chemicals. These chemicals can have serious effects on the waterways ecosystem, kill fish, and can even contaminate drinking water. This is a serious issue for these and many other reasons.

Dr. Wei-Xian Zhang had previously developed a system for cleaning groundwater and contaminated soil using iron nanoparticles. This method was effective but very expensive, averaging $100 for a kilogram of these nanoparticles. In recent work, Dr. Zhang and fellow colleague Dr. Luming Ma invented a much more efficient and cost effective method. By using ordinary scrap iron that you might find in a junk yard, Dr. Zhang was able to devise a method for treating water being discharged from factories.

By adapting the standard technique for treating wastewater, Dr. Zhang’s created a method that passes water through iron filings held in large tanks. The industrial chemicals are attracted to the surface of the iron filings, which have a large surface area. Scrap iron can be purchased locally for 20 cents a kilogram and after being coated with a solution of copper chloride to increase the effectiveness, costs only rise about another 5 cents. This techniques effectiveness is much greater than the biological treatment method. The amount of nitrogen removed goes from 13% to 85%, phosphorus from 44% to 64%, and colors and dyes from 52% to 80%.

This discovery could make a huge impact on the way factories such as pharmaceutical companies, textile factories etc… dispose of contaminated wastewater. The external costs of such pollution are quite large. By developing a more effective and less expensive method, Dr. Zhang has in turn lowered the companies MAC (Marginal Abatement Cost). The MAC is how much it costs for companies to clean up pollutants in the water. By drastically lowering the cost of cleaning the wastewater, factories will be able to abate more pollutants than before and at a much lower cost.

The benefits to society from factories discharging less contaminated water are clear. The external costs will be much less and this new technology will enable and encourage factories to willingly do so because of increased efficiency and decreased costs. The added benefits of buying the scrap metal from local junk yards near the factories are important to look at as well. Instead of having these materials pile up in landfills, they would be put to good use and the amount of revenue collected from them would help stimulate the local economy. This discovery benefits society, the environment, the factories, and the scrap metal companies.
--James Stierhoff