Used for purifying water since the late 1800s, ozone is effective for both destroying microbes and removing contaminants. Ozone, an unstable, pure form of oxygen, reacts rapidly with other molecules and treats water within minutes. According to Wilkes University, ozone is well-suited for both small- and large-scale water treatment. Its effectiveness depends on careful maintenance of the ozone equipment and assessment of water quality before and after treatment.
Contaminants
Ozone is best-suited to treat water that may be contaminated with small microbes such as viruses, amoebas and bacteria. The ozone attacks these organisms by releasing weakly-bonded oxygen atoms from the ozone molecule. The free oxygen atoms, called free radicals, damage many biological molecules. This works rapidly, so after a few minutes, no ozone remains in the water. The free oxygen atoms also bond with dissolved metals such as iron and manganese, forming solids that can be filtered out of the water before consumption.
Production
Two main methods are used to produce ozone for water purification. The first, called corona discharge, runs a high voltage through air. The high voltage produces ozone from naturally occurring oxygen. Larger purification plants use corona discharge, as it produces large amounts of ozone. Smaller-scale processing systems usually use an ultraviolet (UV) light ozone-production method.
Assessment
While ozone effectively removes many contaminants, some things present in water require further steps or another treatment option. Ozone won't remove heavy metals, like lead and mercury. It might not destroy larger microbes such as giardia and cryptosporidium effectively. Ozone changes dissolved bromides into cancer-causing bromates. For this reason, you must assess the water before creating a treatment process and purchase equipment.
Maintenance
After treatment with ozone, metal compounds form undissolved solids that must be filtered out of the water. The treatment system should also filter biological fragments from destroyed organisms. Periodically, you need to clean or replace these filters, inspect the system, check high-voltage electronic parts, or replace an ozone-generating UV lamp. You cannot rely on a treatment system unless it has been carefully maintained.
Energy Consumption
Most ozone-generating techniques require a steady supply of electricity. For remote locations or circumstances where electric power is unreliable or nonexistent, you'll need to consider other treatment options. If you're estimating the costs of treatment, include the local cost of electricity in your calculations.
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