1. 0.003%

2. 2/3 evapotranspires, 1/3 runs off, and 3% infiltrates into the groundwater.

3. First is agriculture, followed by industry and public/municipal

4. Define the following terms:

• zone of aeration: upper soil layer that holds both air and water
• zone of saturation: usually lower soil layer where all available pores between soil particles are filled with water
• water table: the top of the zone of saturation
• aquifer: groundwater that is economically retrievable
• recharge area: where water is added to an aquifer
• discharge area: where water is removed from an aquifer (e.g., wells, springs, rivers, etc.)
• ground water mining: removing water from an aquifer faster than it is replenished (discharge rate greater than recharge rate).

5. pollute or decrease infiltration rates

6. problems associated with overpumping groundwater

• Higher costs associated with digging deeper wells and pumping water farther up.
• Lower water quality
• Loss of habitat (loss of riparian habitat and species associated with springs, rivers, etc.)
• Subsidence: as water is removed from the ground, the soil compacts and the surface sinks which damages structures (e.g., roads, pipes, buildings, etc.) and may lead to "permanent" loss of water holding capacity for the aquifer.
• Saltwater intrusion: occurs in coastal areas when overpumping freshwater groundwater begins to suck salt water into an aquifer and saltwater gets pumped into wells.

7. Point sources of pollution are discrete, identifiable sources of pollution (e.g., pipe dumping polluted water into a stream) which are more easily monitored and enforced).
Nonpoint sources of pollution are diffuse or scattered sources (e.g., oil off roads) which are more difficult to monitor and enforce.

8. Three major types (stages) of wastewater treatment

• Primary Treatment: physical/mechanical processes
• Secondary Treatment: biological processes
• Tertiary Treatment: processes used to remove specific pollutants

9. How does the Roger Road Wastewater Treatment Plant do each of those three?

• Primary Treatment: screen, grit chamber, primary/secondary sedimentation tanks (clarifiers)
• Secondary Treatment: biotowers full of aerobic organisms and digesters filled with anaerobic organisms, and chlorine contact chambers
• Tertiary Treatment: de-chlorination

10. See answer below:

• Screen: large objects are screened out and trucked to landfill.
• Grit Chamber: heavy objects settle out, are air-lifted out, and trucked to landfill.
• Primary Sedimentation Tanks (Primary Clarifiers): lighter suspended solids settle to the bottom and grease floats on top and both are pumped to the Sludge Thickeners.
• Biotowers: colonies of aerobic (oxygen-needing) bacteria and other organisms growing on specially designed plastic media consume the organic waste from the primary effluent.
• Secondary Sedimentation Tanks (Secondary Clarifiers): suspended solids (including organisms washed out of the biotowers) settle to the bottom and grease floats on top and both are pumped to the Sludge Thickeners.
• Chlorine Contact Chambers: secondary effluent is chlorinated to kill remaining organisms.
• [Some of the effluent water is diverted here to go to the city for further treatment and use for irrigation]
• De-Chlorination (Tertiary Treatment): chlorine is removed from effluent with sodium metabisulfate and effluent is released into the Santa Cruz River directly.
• Sludge Thickeners: sludge from the sedimentation tanks is thickened by removal of some water.
• Digesters: heated tanks where the solids are broken down by anaerobic bacteria (live only without oxygen). Methane gas is produced by the bacteria and is used to power the treatment plant.
• Ina Road Centrifuge: sludge from digesters is pumped 5.3 miles to be centrifuged (removes more water) and then the sludge goes to the agricultural industry to be used to fertilize non-food crops such as cotton.
• In conclusion: solids removed by initial screens and grit chambers go to the landfill and biosolids (sludge) removed from clarifiers go to agricultural fields to fertilize non-food crops (like cotton). Some of the effluent (treated water) goes to the city for further treatment and used to water golf courses, parks, athletic fields, etc., but most of the effluent is dumped into the Santa Cruz River where it flows north toward Marana (the water evapotranspires and infiltrates into the groundwater).