Harwich Water Deparment - Water Conservation & Protection

DO CLEAN DISHES MAKE DIRTY PONDS?

PHOSPHORUS: ACTION HOMEOWNERS CAN TAKE TO PROTECT LAKES AND PONDS

WHY IS PHOSPHORUS A PROBLEM?
Excess phosphorus from land-based activities degrades the health of fresh water bodies. Phosphorus is a natural element essential to plant growth. However, contributions of this chemical from human activities can lead to a nutrient imbalance in ponds, which fuels the overgrowth of algae and aquatic plants. This accelerated growth leads to depletion of oxygen, causing fish kills and a stagnant, murky look to the water. Phosphorus is introduced to a water body via direct contributions of phosphates from runoff and fertilizer use, and indirectly from septic system effluent in the recharge area.

Studies have indicated that phosphorus can travel several hundred feet with the groundwater before it becomes bound to soil particles. Lot sizes in many established neighborhoods around water bodies are generally small - in the 8-12,000 square foot range. Given the traveling range of phosphorus, homes two to three rows back from the water's edge are also likely contributors to the overload.

WHAT CAN INDIVIDUAL HOMEOWNERS DO?
We can reduce the amount of phosphorus entering our septic systems by evaluating the products we use in our homes. Phosphates are present in varying amounts in soaps, detergents and cleaning compounds. By reading labels and becoming familiar with phosphorus content, homeowners can make a major impact in water quality by the relatively simple act of product purchase.

Most consumers are aware of the effort to compel soap manufacturers to lower and or remove phosphates from laundry detergents. This is not the case with other types of detergents, and in particular, automatic dishwashing detergents. The presence of dishwashing machines has changed from an optional appliance in the home of a generation ago to an expected, standard convenience today. Therefore, the type of dishwasher detergents used is a determining factor in the amount of phosphorus in domestic sewage.

The following table shows concentrations of phosphorus in commonly available dishwasher detergents and the estimated cumulative discharge of phosphates from their use:

^Tablets are concentrated formulations
Data in above table compiled by the Great Sand Lakes Task Force, Harwich, MA, June, 1993***

HOW MUCH PHOSPHORUS IS TOO MUCH?
While it is difficult to quantify how much phosphorus is required to produce algae blooms in a pond, we do know that the natural state of a healthy pond involves no artificial inputs of phosphorus. With each discharge of phosphate laden wash water in close proximity to a pond, there is a shift in the natural chemical balance in that pond. Eventually, the cumulative impact of relatively small phosphorus contributions will be the production of excess algae and aquatic plants.

CAN WE REALLY MAKE A DIFFERENCE?
If enough people within the critical band of homes around a pond choose phosphate-free detergents, the threat of algae problems from detergent sources will be lessened. After reading this, be sure to consider that it is up to each consumer to act responsibly in purchasing and using products that are environmentally friendly, in order to protect our natural resources at minimal cost. Doing so can only help to preserve pond quality. So choose wisely and tell your neighbors why you did!

* Grams per use phosphates based upon the average use of 1/3 cup of detergent used per cycle
** Pounds per year phosphates based upon an average of 3 uses per week of an automatic dishwasher
*** Great Sand Lakes Task Force, c/o Harwich Board of Health, Paula Champagne, Health Director, 732 Main St., Harwich, MA 02645.