Joey Robison, Cannon River Watershed Partnership

Who would have thought that having clean dishes would mean having green lakes?

Phosphorus was once widely used in household detergents. It was a useful ingredient: phosphates reduce water hardness, suspend certain types of particulate matter, prevent them from being redeposited, and aid in killing germs. But over time it became clear that this seemingly beneficial cleaning product additive could have very detrimental effects on our environment.

Phosphorus is a fertilizer, and automatic dishwashing detergents can contain as much phosphorus as all-purpose houseplant fertilizer. In aquatic systems, excessive phosphorus results in algae blooms. Overabundance of algae and the resulting microorganisms can be very detrimental to fish populations and other aquatic life.

Removing phosphorus from wastewate r is difficult and costly. On average, wastewater treatment plants in the watershed remove about 40- 60% of the total phosphorus that comes in with wastewater. That means that approximately half of the dissolved, immediately usable form of phosphorus is not removed and is deposited into our waterways.

In the 1960’s it was estimated that about 50% of the phosphorus found in wastewater came from laundry detergents. In 1976, Minnesota passed legislation limiting the phosphorus content in laundry detergent (and all household cleaning agents intended for home use) to 0.5% phosphorus by weight. Automatic dishwashing detergents, however, were exempt from this rule. Because a dishwasher can have as many as five wash cycles (unlike a washing machine which only has one wash cycle), it needs something that will soften the water in each cycle. It was assumed that there was no other alternative to phosphorus for this task.

Thirty years ago, few homes had automatic dishwashers, so it wasn’t thought to be a large source of phosphorus. Today, almost everyone has one - a Montana survey found that over 75% of the households surveyed had an automatic dishwasher. Now it is estimated that 8-15% or more of the phosphorus leaving a wastewater treatment plant is from automatic dishwashing detergent.

Purchase Phosphate free dishwashing detergent. Our lakes are worth it.

Recent state legislative efforts have supported a bill that would set limits on or remove phosphorus completely from automatic dishwashing detergent. This small step would cost the state nothing but would save significant time and money by taking care of the problem at the source instead of treating it after the fact.

You can start today by purchasing phosphate free automatic dishwashing detergent. If your store doesn’t carry it, ask them to. It may cost a few cents more per load, but our lakes are worth it. Visit Cannon River Watershed Partnership’s website for a list of phosphorusfree dishwasher detergents.

P.S. The state legislature chose not to ban phosphorus in dishwasher detergent during their past session, but rather to set up a study to identify and quantify all the sources of phosphorus

Posted in Lakes |