Laundry Products Research
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Lanfax Labs in association with Choice tested 49 powder  detergent concentrates in early 2007, resulting in "Wash Only" data for 35 powders in front loaders and 35 powders in top loaders.  The report was published in "Choice" in the April edition.  The data below extend to dual testing of products where one brand was suitable for both front and top loader. These data are presented independently of "Choice".

 

Sodium and Phosphorus - combined assessment

This graph is similar in format to one that has been available on this website for many years but has recently been withdrawn because it displayed research done in 1999.  The products listed below were obtained in January 2007.  The purpose of combining the two graphs is for those consumers who are interested in reducing either or both sodium and phosphorus.

Interpretation
On soils and for vegetation where sodium is an issue, choose a product that has a very short blue bar. Ideally, because the average household does seven loads of washing per week and discharges its wastewater over an equivalent area of about 200 square metres (calculations from experience in designing on-site wastewater systems consistent with AS/NZS 1547:2000), any salt loading over 22 g/wash is more than one tonne of sodium chloride equivalent (common salt) per hectare per year. Since greywater systems typically have smaller irrigation areas, irrigation from the washing machine over 100 m2  for a sodium load of 11 g/wash is equivalent to 1 tonne common salt per hectare. At this rate, many plants will be adversely affected by sodium and some soils will start to lose their structural stability.  See the calculation at the bottom of the page labelled SODIUM.

Whether your situation is one that requires minimisation of phosphorus will depend upon whether you discharge your wastewater to land application areas to promote plant growth, or whether you discharge to sewer that eventually finds its way into river systems.  Phosphorus is an essential plant nutrient and if you don't put it on with wastewater, then it will have to be put on from other sources or you are just mining whatever natural fertility may be there.  The length of the red bar shows the concentration of phosphorus in milligrams per litre (mg/L).  The shorter the bar, the lower the concentration.  Some products have very little phosphorus.

It is unfortunate that in many municipal treatment works, sewage is treated with chemicals to remove the phosphorus and then the phosphorus laden sediment is buried in landfills. As phosphorus is a non-renewable resource, burying this sludge is environmental ignorance.

Sodium and Phosphorus in "wash" only volume of water

 

 

 

Suggested area of garden or lawn
Based upon simple calculations of sodium loads to soil, a rule-of-thumb could be that for each gram of sodium per wash at least 10 m2 of lawn or garden area is required to discharge the water from the wash cycle of either a top loader or a front loader.  For the front loaders, an area of at least 500 m2 would be required.  For most urban blocks, such land areas are not available.

Discharging the washing machine's "wash" water through a small garden hose over perhaps 10 m2 of garden is likely to be extremely detrimental to both plants and the soil.