b'Chapter 4Out of Sight, Out of Mind:We cannotush our troubles away. What goes A Wastewater Primerdown the drain eventually re-enters our food H uman wastes carry chain.viruses, bacteria, antibiotics, andnutrients and must be disposed of with care. These bacteria are not suited to survive for long outside the human body; however, the viruses and nutrients can persist. If not carefully disposed of, wastes can contaminate drinking water. The nutrients contained in wastewater, especially nitrogen, can also aff ect the quality of drinking water and cause a serious decline in coastal marine habitat, wiping out eelgrass and shellfi sh beds. Toxic materials, including prescriptions,should never be disposed of in your septic system. They may seep into the groundwater, contaminating drinking water and the food chain.Wastewater Treatment:A Brief HistoryFind out what treatment theHistorically, the goal of treatment is to remove the disease-causing pathogens wastewater fromand dissolve the solids enough to be able to dispose of the wastewater in the soil. your householdHuman beings have a long history of disposing of their wastes into the ground. receives before it re-enters theThis method isolated wastes and allowed natural chemical and biologicalenvironment. processes to break down solids and destroy the pathogens. But this only worked as long as the population remained small. The addition of clean water to carry the waste out of the dwelling and into cesspools was a natural next step. However, the water also leached nutrients, viruses, and to a lesser extent, bacteria away from the cesspool, and toward the water sources.Modern wastewater systems contain two components: the tank and the soil absorption fi eld. The septic tank was a step forward from the cesspool because it provided a watertight tank to store the solid wastes and release the liquid slowly to infi ltrate into the ground. Separating the solids from the liquids is called primary treatment. It helped prolong the life of the soil absorption system by removing grease and solids that once clogged the soil around cesspools. Page 25bluepages.indd 25 8/26/2009 1:50:22 PM'