Sludge bulking
Encyclopedia
In treatment of sewage
one process used is the activated sludge
process in which air is passed through a mixture of sewage and old sludge to allow the micro-organisms to break down the organic components of the sewage. Sludge is continually drawn off as new sewage enters the tank and this sludge must then be settled so that the supernatant can be separated to pass on to further stages of treatment.
Sludge bulking occurs when the sludge fails to separate out in the sedimentation tanks. The main cause of sludge bulking is the growth of filamentous bacteria
.
Filamentous microorganism
s grow in long strands that have much greater volume and surface area than conventional floc and are very slow to settle. Under certain growing conditions, filamentous organisms predominate. There is little robust scientific evidence that can be used to avoid sludge bulking but what there is indicates that over-loading works, having a carbohydrate rich input and having too low a recycle rate may all contribute.
To avoid sludge bulking some of the flow that enters the reactor can be by-passed, recycle ratio can be increased, lime or soda can be added to the reactor or the re-aeration rate increased.
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...
one process used is the activated sludge
Activated sludge
Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans.-Purpose:...
process in which air is passed through a mixture of sewage and old sludge to allow the micro-organisms to break down the organic components of the sewage. Sludge is continually drawn off as new sewage enters the tank and this sludge must then be settled so that the supernatant can be separated to pass on to further stages of treatment.
Sludge bulking occurs when the sludge fails to separate out in the sedimentation tanks. The main cause of sludge bulking is the growth of filamentous bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
.
Filamentous microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s grow in long strands that have much greater volume and surface area than conventional floc and are very slow to settle. Under certain growing conditions, filamentous organisms predominate. There is little robust scientific evidence that can be used to avoid sludge bulking but what there is indicates that over-loading works, having a carbohydrate rich input and having too low a recycle rate may all contribute.
To avoid sludge bulking some of the flow that enters the reactor can be by-passed, recycle ratio can be increased, lime or soda can be added to the reactor or the re-aeration rate increased.