Chapter 14 Biological Waste Water Treatment
Chapter 14 Biological Waste Water Treatment
Main end products of the main waste water impurities in the three main process ypes employed for waste water purification Process type Impurity Aerobic Anoxic Anaerobic Organic carbon CO2+biomass CO2+biomass CO2+CHa+biomass Nitrogen NO3+biomass N2+biomass biomass Phosphorous biomass biomass biomass Heavy metals biomass biomass biomass
Process type Impurity Aerobic Anoxic Anaerobic Organic carbon CO2+biomass CO2 + biomass CO2+CH4+biomass Nitrogen NO3 - +biomass N2+biomass biomass Phosphorous biomass biomass biomass Heavy metals biomass biomass biomass Main end products of the main waste water impurities in the three main process ypes employed for waste water purification
14.1 Characterisation of the waste water (w 6)uondwnsuo -20C 300 200 5C 100 ua6fxo 0 0 10 20 30 Time(days) Oxygen consumption profiles of waste water at two different temperatures. COD=aBODz-b
COD=aBOD7 -b 14.1 Characterisation of the waste water
BOD COD
BOD COD
14.2 Aerobic processes for BOD removal 14.2.1 Microflora of aerobic processes Examples of bacteria often reported from investigations on the microflora of aerobic waste water treatment Organisms Comment Achromobacter Common water and soil bacteria Acinetobacter Utilised for phosphorous removal Alcaligenes Common water and soil bacteria.Important denitrifyer Bacillus Producer of extracellular hydrolytic enzymes Beggiatoa Filamentous bacteria stimulated by high sulphur content Corynebacterium Common water and soil bacteria Escherichia coli Introduced from faeces,together with other enteric bacteria,but not considered important in the process. Flavobacterium Common water and soil bacteria Methanogenic bacteria Obligately anaerobic methane producing bacteria.See Chapter 14.1 Microthrix Filamentous bacteria stimulated by low sludge load and high fatty acid content.May cause sludge bulking. Nitrobacter Obligate aerobe and litoautotroph which oxidises NO2-to NO3- Nitrosomonas Obligate aerobe and litoautotroph which oxidises NH3 to NO2- Nocardia Filamentous actinomycete associated with foaming in the activated sludge process Pseudomonas Important denitrifyer.Utilise a wide spectrum of carbon sources. Sphaerotilus natans Filamentous bacteria that can cause bulking of the sludge. zoogloea ramigera Producer of extracellular polysaccharides. Utilises a wide spectrum of carbon sources Believed to be important for flocculation and biofilm formation
14.2.1 Microflora of aerobic processes 14.2 Aerobic processes for BOD removal
14.2.2 The activated sludge process n Out Air Sludge Principle design of an activated sludge reactor with an aerated compartment (left) and a sludge separator(right). CoHO,Ns+O2>CO2+H2O+NH3 +biomass WH3-→NO2→NO→N2
C H O N + O → CO + H O + NH + biomass 2 2 2 3 NH3 → NO2 → NO3 → N2 − − 14.2.2 The activated sludge process
里 得 , H..co
purification =100 Si-So Si and So are the Si concentrations of pollutant in the inlet and outlet flows sludgeload FS, Fi is the rate of incoming water to a reactor volume Vreact with sludge concentration Xreact react Sludge age (days) 脉= δis the SF separation factor
Si Si So purification − =100 react react i i V X FS sludgeload = i F V x react = Si and So are the concentrations of pollutant in the inlet and outlet flows Fi is the rate of incoming water to a reactor volume Vreact with sludge concentration Xreact Sludge age (days) δ is the separation factor
女 100 0 0 Sludge age (e) Sludge load Fig 19.3 Principle dependence of the purification on the sludge age and the sludge load
14.2.3 Biofilm based processes Out Sludge Schematic design of trickling filter(above)and rotating disc reactor(below)with sludge separators
14.2.3 Biofilm based processes
