The chemical formulation of a detergent involves numerous compounds that can be classified into three general categories: surfactant, builder, and miscellaneous. Miscellaneous ingredients include dyes and fragrance.
The surfactant of a detergent functions as a wetting agent. Surfactant molecules form links between dirt particles and water because of their bipolar nature. One end of the molecule is polar to interact with water, while the other end is hydrophobic (nonpolar) and interacts with dirt and oil. The most commonly used surfactants are compounds known as linear alkyl sulfonates (LAS). Typical members of this group are shown in the black-and-white structures here.
The main role played by the builder in a detergent is that of a sequestering agent, which tie up the ions causing water hardness (Ca2+ and Mg2+). In one type of dishwashing liquid, marketed as environmentally friendly, these compounds appear to be lactic acid and denatured alcohol. http://www.colgate.com/app/Palmolive/US/EN/Product-Ingredients.cwsp?product=UltraPureClear#UltraPureClear
Previous to 1965, polyphosphates were used as builders, but due to their breakdown to phosphates, which are considered a nutrient. When natural waters are enriched with nutrients, a process called eutrophication ensues. This can lead to ecological imbalances since this process normally (naturally) takes thousands of years. Human contributions as of 1972 have caused up to 70% of detergent buildup in waste waters. These molecules do not appear to be used in dishsoap, but perhaps more commonly found in laundry detergent since they are safe for use in cleaning all types of colors, fabrics, and fibers (especially synthetic).
An alternative to polyphosphates that is found in a dishsoap that is not marketed as environmentally friendly is sodium pentetate. http://www.colgate.com/app/PDP/Ajax/US/EN/dishLiquid.cwsp Its structure is shown in color here. A predecessor to this modern form is nitrilotriacetate (NTA) of the general formula N(CH2COONa)3. NTA does not degrade in anaerobic conditions and complexes heavy metals (such as cadmium or mercury). A possible result is increased transmission of these metals across the placental barrier and into a fetus, thereby increasing the likelihood of birth defects.
Recently, we switched from Tide Pods to Kirkland Signature Environmentally Friendly Laundry Detergent. A list of ingredients comparing their role between the two brands is attached at the bottom of this post. We aren't currently equipped to reclaim our laundry grey water, whereas it's much easier to capture the dish water since we don't have a dishwasher. We just wash dishes in a bin within the sink and then use the greywater to keep the garden green.
We also went through a phase of using a bucket in the shower to capture excess greywater there. We switched to environmentally friendly shampoo and conditioner (or at least all-natural) TRESemme Naturals Nourishing moisture shampoo and Avalon Organics Lavender Nourishing Conditioner. They didn't seem to harm the plants, but it didn't last long since it was so awkward having a large bucket in the shower.
It would be a large undertaking to catalog all the molecules in all of these products and prepare a comparative analysis of each ingredient's risks and benefits from a consumer and environmental standpoint. This is a long-term project for us at the Kaiser Wellness Center and we hope someday to formulate our own environmentally responsible products. Until then, we can rely on our friends who are currently manufacturing soaps and lotions under the brand CT Organics. This way the products are not only safe but locally produced.
Our experiment with simulated greywater, Palmolive Ultra Pure+Clear and its effect on Swiss Chard is cataloged here.
Works Cited:
Stoker, S. H. and Seager, S. L. Environmental Chemistry: Air and Water Pollution. Scott, Foreman and Comapany, Glenview, IL (1972), Paperback. Chapter 11: Detergents, p. 142-151.