Columbia subject headings:
Microorganisms--Dispersal--United States.
Water--Microbiology--United States--Costs.
Water--Purification--United States--Costs.
Harvard subject headings:
Microorganisms--Dispersal--United States.
Microorganisms--United States--Dispersal.
Water--Microbiology--United States--Costs.
Water--Purification--United States--Costs.
Princeton subject headings: