in hot climates requirements particularly from Generally sub-divided into No mechanical the anaerobic anaerobic ponds, facultative installations ponds ponds and maturation ponds Very simple method Sensitive to of treatment temperature variations Constructed Are an artificia Have substantial High land wetlands created for capacity for requirement Used in conjunction with waste wastewater treatment Requires relatively stabilisation systems for refining flat or gentle slopes the quality of effluent Requires specific aquatic plants Appropriate for small institutions Aerated lagoons A more intensive system of Detention time less High O&M treatment resulting in greater than in stabilization requirements removal of organics per unit ponds volume of treated wastewater Less land than in WSPs. requirement as Oxygen is supplied to wastewater compared to WSP by aerators floating or fixed in the lagoons. Oxidation An extended aeration Relatively low land High O&M ditches plant best suited to small requirement and requirements communities. suitable where land is Not effective in The aeration tank is in the form at a premium price. removing Faecal of a long continuous channel, Coli Form. oval in plan and with rotor suspended over the channel for aeration, mixed liquor propulsion and prevention of suspended particles from settling out. Sewage is evenly distributed on Durability in all Percolating/Trickling Limitation in the surface and effluent collected weather conditions filters volumetric loading through under drains that also and in the presence of Significant loss of help in aeration. corrosive effluents head Does not upset for The units are preceded by settling Nuisance due to variation of hydraulic tanks to collect the settle able flies or organic loading organic solids delivered from the Medium O&M filters. cost Any degree of Sensitive to Activated sludge Involves aeration of settled treatment is possible organic sewage mixed with return sludge process Final effluent is clear loading within an aeration tank during and odourless particularly for which time the micro-organisms Low land industrial wastes in the sewage multiply through requirement which result in assimilation of the organics in the Freedom from odour bulking of sludge nuisance High O&M influent wastewater.
in hot climates Generally sub-divided into anaerobic ponds, facultative ponds and maturation ponds requirements No mechanical installations Very simple method of treatment particularly from the anaerobic ponds Sensitive to temperature variations Constructed wetlands Are an artificia created for Used in conjunction with waste stabilisation systems for refining the quality of effluent Have substantial capacity for wastewater treatment High land requirement Requires relatively flat or gentle slopes Requires specific aquatic plants Appropriate for small institutions Aerated lagoons A more intensive system of treatment resulting in greater removal of organics per unit volume of treated wastewater than in WSPs. Oxygen is supplied to wastewater by aerators floating or fixed in the lagoons. Detention time less than in stabilization ponds Less land requirement as compared to WSP High O&M requirements Oxidation ditches An extended aeration plant best suited to small communities. The aeration tank is in the form of a long continuous channel, oval in plan and with rotor suspended over the channel for aeration, mixed liquor propulsion and prevention of suspended particles from settling out. Relatively low land requirement and suitable where land is at a premium price. High O&M requirements Not effective in removing Faecal Coli Form. Percolating/Trickling filters Sewage is evenly distributed on the surface and effluent collected through under drains that also help in aeration. The units are preceded by settling tanks to collect the settle able organic solids delivered from the filters. Durability in all weather conditions and in the presence of corrosive effluents Does not upset for variation of hydraulic or organic loading Limitation in volumetric loading Significant loss of head Nuisance due to flies Medium O&M cost Activated sludge process Involves aeration of settled sewage mixed with return sludge within an aeration tank during which time the micro-organisms in the sewage multiply through assimilation of the organics in the influent wastewater. Any degree of treatment is possible Final effluent is clear and odourless Low land requirement Freedom from odour nuisance Sensitive to organic loading particularly for industrial wastes which result in bulking of sludge High O&M
Environmental00uja0and0Thika0South.docx