Calcium Carbonate Scale Dissolution in Water Stabilized by Carbon Dioxide Treatment.

摘要

Calcium carbonate scale in potable water systems (especially hot-water pipes and exchangers) can restrict pipe flow, causing severe head loss and reducing heat transfer capacity. Chemical and mechanical methods of cleaning the distribution systems are considered unsafe for potable supplies due to the human health hazard. As a result, the only alternative may be complete pipe replacement--which can be very expensive. The U.S. Army Construction Engineering Research Laboratory (USACERL) and Illinois State Water Survey have jointly developed a carbon dioxide treatment system for rehabilitating clogged pipes and controlling scale buildup in nonfouled systems. The treatment method is safe and effective. It is being field-tested successfully at several Army installations. Information is needed on the the characteristics of scale dissolution for optimizing the treatment system because overdoses of carbon dioxide can eventually damage pipes. Therefore, USACERL has explored several models for predicting the effects of carbon dioxide treatment on potable waters. A theoretical model was formulated and used in developing a computer program for assessing a water's propensity to become undersaturated, saturated, or oversaturated with respect to carbon dioxide, and to determine its capacity for calcium carbonate deposition or dissolution. Keywords: Drinking water; Calcium carbonate scale; Carbon dioxide treatment; Pipe rehabilitation. (kt)