Phosphates in detergents - Cleaning up our act

Abstract

Water quality The shockingly green pictures of Hartbeespoort Dam algal blooms have, for a long time, set the visual scene for studies and articles addressing the subject of the excessive amounts of nutrients we are pouring into our rivers and dams. Although almost synonymous with it, algal blooms and nutrient enrichment problems are not unique to Hartbeespoort, and managers of impoundments around the country are noticing rising levels of chlorophyll a in their water quality samples. A related subject that has also often been discussed is the contribution that powdered laundry detergents make to this problem. In fact, in South Africa, about 23% of a laundry detergent’s mass is made up of sodium tripolyphosphate (STPP). This ingredient’s jobs is to act as a water softener and to bind up ions which reduce the effectiveness of the detergent. However, when it is mixed with water, STPP quickly hydrolyses to ortho-phospate (or soluble reactive phosphate – SRP), a nutrient which is important to the growth and survival of all living organisms.

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