16Sludge digestion is usually:AAnaerobic, producing methane (biogas)BDone by filtrationCChemicalDAerobic onlyView AnswerDiscussWorkspaceReportSaveEasy
17An oxidation pond treats sewage using:AChemicals onlyBBacteria and algae in a symbiotic relationshipCUltraviolet lampsDFiltersView AnswerDiscussWorkspaceReportSaveEasy
18A soak pit is used with a septic tank to:ALet the effluent percolate into the groundBCollect rainwaterCStore sludgeDTreat drinking waterView AnswerDiscussWorkspaceReportSaveEasy