Table 6.2 Clogging types, causes, diagnosis and methods for management Clogging Minimisation mechanism and prevention and C Renovation technique u water or frequently deep systems) Basin scraping • Air deposited in Improve Photography entrainment, • • pipes pretreatment (basins) and gas binding Analyse • Treatment • down-hole TV Adjust water • byproducts camera survey source-water temperature (eg alum) pH or cation and specific Algal growth in • gases concentration basins Avoid or • remove dissolved oxygen in Filtration of source water suspended Backwash • solids more frequently TSS, turbidity, • Redox reactions • MFI, particle Incompatibility size • Pumping • between source distribution of Waiting for gas water, • source water groundwater to and and aquifer soil/aquifer materials Bypass • Improving Presence of • filter • well design reactive clays testing (swelling/disper Changes • sion) in specific capacity (wells) Avoid • Chemical cascading Pumping • precipitation, Gas trap Surging • • ion exchange Jetting Degas source • • water Basin drying or • • Prevent • reactions • (eg N2 falling production) water analyses Presence Improve • (especially • of gas in pretreatment of redox source source water, conditions and water especially mineral • removal of saturation suspended indices) solids SEM analysis reactions • of backwash Prevent light • water (algal Pumping or soil and growth) • aquifer Backwash Wire • • • wells or dry samples brushing (scrapes of out basins in Acid • well face for more source treatment
Table 6.2 Clogging types, causes, diagnosis and methods for management Clogging mechanism Minimisation and prevention Renovation technique and Air entrainment, gas binding Filtration of suspended solids Chemical precipitation, ion exchange • falling water • Presence of gas in source water • reactions • in source water or deposited in pipes • Treatment byproducts (eg alum) • Algal growth in basins • Redox reactions • Incompatibility between source water, groundwater and aquifer materials • Presence of reactive clays (swelling/disper sion) • Avoid cascading • Gas trap • Degas source water • Prevent reactions (eg N2 production) • Improve pretreatment of source water, especially removal of suspended solids • Prevent light (algal growth) • Backwash wells or dry out basins more frequently • Improve pretreatment • Adjust source-water pH or cation concentration • Avoid or remove dissolved oxygen in source water • Backwash more frequently • Pumping • Waiting for gas to • Improving well design • Pumping • Surging • Jetting • Basin drying or • Pumping • Wire brushing • Acid treatment • Basin scraping • Analyse water temperature and specific gases • TSS, turbidity, MFI, particle size distribution of source water and soil/aquifer • Bypass filter testing • Changes in specific capacity (wells) • analyses (especially redox conditions and mineral saturation indices) • SEM analysis of backwash water or soil and aquifer samples (scrapes of well face for deep systems) • Photography (basins) and down-hole TV camera survey C u
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