Between Sea and Earth — Protecting an Essential Buffer

Radioactive isotopes, or 'radiotracers', are used to precisely measure the purification efficiency of wastewater facilities and drinkable water production facilities, aiding their design and improving their performance. Minute quantities of radiotracers can be reliably detected in large-scale processing, such as treatment plants handling millions of litres of effluent daily. Sewage sludge, which normally would be released into waterways, can be irradiated to produce both fertilizer and sterile water for agriculture, improving crop yields, food safety and reducing the demand for fresh water. Isotopic techniques are used to map how sediment moves, ensuring that dredged material can be released in an area where it cannot migrate into ecologically sensitive regions or return to the dredged harbour. Industrial effluent can be treated using radiation without adding any other chemical substances or generating radioactivity. This technique can be used to clean wastewater and reclaim water for use in industry and agriculture. Irradiation removes persistent organic pesticides and toxic compounds. An electron beam can irradiate wastewater containing chemicals that resist being broken down with heat, such as those used in manufacturing textile dyes. After irradiation these chemicals are either rendered harmless or converted to substances that are easily removed by using conventional treatment techniques.