In Search of Ideal Groundwater Treatment
As surface water supplies become increasingly polluted and difficult to treat, the use of groundwater continues to increase. Every day, more than 77 billion gal of water are withdrawn from aquifers for a variety of uses including human consumption.
Worldwide, groundwater makes up 95% of available freshwater, and nearly half of the U.S. population receives all or part of its drinking water from the ground, according to the National Ground Water Association. Small community water treatment plant operators, limited in the resources and finances necessary to meet the stringent and ever-changing U.S. EPA surface water treatment rule, are leading the way toward increased use of groundwater.
Groundwater is an under-utilized commodity that is both renewable and reliable. Deep-drilled wells can recharge themselves, providing a steady supply of water that will not fluctuate with atmospheric changes. As groundwater moves downward to aquifers, however, it dissolves minerals it contacts. Those dissolved minerals give groundwater its chemical character and quality. Some undesirable qualities, such as dissolved iron, manganese or sulfides, can cause aesthetic problems such as staining or odor. Other compounds like arsenic, cyanide or nitrites can have serious health implications.
In small community water treatment systems, ozone is increasingly being used as a chemical oxidant in the early stages of water treatment to oxidize organic and inorganic contaminants. Ozone works faster than any other oxidant currently used in water treatment and results in the formation of fewer undesirable byproducts. Many organics will be completely oxidized, while inorganics readily precipitate for simple filtration. The oxidation of organic compounds can lead to many benefits including color and odor removal, and taste and algae control.
If membrane filtration is used as the primary treatment option, partial oxidation of organics can result in microflocculation, aiding filtration of compounds that can lead to THM formation.
Pretreatment with ozone will enhance feedwater quality to filtration membranes, allowing for longer filter life and superior product water.
1. When properly utilized, ozone provides many advantages.
- Strongest single oxidizing agent available—152% stronger than chlorine over a broad pH range;
- Generated on site—no transportation, handling or storage required;
- No disinfection byproduct formation;
- No residual in plant effluent;
- No added taste;
- Reverts to oxygen, simplifying water chemistry; and
- Minimizes use of persistent biocides prior to final distribution.
2. Ozone can be utilized in various applications.
- Private household wells;
- Small community wells (systems serving fewer than 10,000 people);
- Municipal wells (systems serving greater than 10,000 people);
- Irrigation wells;
- Drinking water for livestock;
- Industrial and commercial ground- water supply for process water used in industries such as food processing, bottled water, beer, paper, semicon-ductor, metals, etc.; and
- Water recycling.
3. Ozone has been proven to be effective in treating various compounds.
- Oxidation of organic compounds such as tannins and lignins; iron and sulfur reducing bacteria; volatile organic compounds; and synthetic organic compounds.
- Oxidation of inorganic compounds such as iron, manganese, sulfides, arsenic, cyanide, nitrites and organically bound heavy metals.
As the search for an ideal groundwater treatment method continues, more companies are discovering the benefits of ozone. Ozone is one of the strongest and most common oxidants being used for in situ chemical oxidation, a treatment method in use since the early 1990s. Low cost and speed of reaction are the two main advantages leading many to apply ozone as a preliminary conditioning, primary treatment or final polishing technique.