Raw Sludge

Taxonomy

• Treatment
• Sludge Separation
• Sludge Treatment
• Sludge Management
• Sludge Treatment & Management

1 Answer

1. The question is not very clear. "If the weir plate is not level, or part of the weir becomes clogged with slime or debris, shortcircuiting will result because more water will pass over the low side or the clean notches of the weir. Short-circuiting will cause poor settling and uneven sludge blanket buildup." This can cause sludge to rise. Also, "Failure to remove sludge often enough will result in anaerobic conditions and gas buildup in the sludge. The sludge can become septic, releasing gas bubbles, and float to the top where it can be difficult to remove".

    

   1 Comment

   1. It would be good to have more details, like type of sedimentation tank, dimensions, is sludge coming regularly, or only during peak flows, how often is discharged from the tank, etc.

      In practice, short circuiting will be observed in number of sedimentation tanks. To determine if short circuiting exist and to what extent, tracer study should be performed. The wrong influent flow distribution in the sedimentation tank will also affect short circuiting.

      Temperature effect as well as wind  effect can be significant in sedimentation basins since it will cause density current to form, which will also influence primary sedimentation tank performance.

      Sludge may be removed from tank more completely and/or more frequently. Scrappers should be checked for proper operation and broken wooden parts should be replaced. If the sludge decomposition takes place in primary sedimentation tank, it will be buoyed to surface.

      Holding primary influent or effluent and associated solids too long generally causes not only septic conditions, but also generates low D.O. conditions. Low D.O. conditions cause the bacteria to generate specific compounds with sulfides and/or organic acids. Holding times of influent should always be kept to a minimum. Generation of septic conditions can also contribute to ashing in the clarifier, since the solids are turning anaerobic in the bottom of the clarifier and generate gases that cause clumps of solids to float to the top. This increases solids carryover.

      Sometimes, anaerobic sludge is sent to the primary clarifier via the belt press supernatant. This can also lead to an increase in septic conditions in a primary clarifier, since you are seeding the system with bacteria that like to grow in anaerobic or facultative conditions. One way to tell if the solids are being held too long in the clarifier is if there is ashing on the clarifier or gassing. Ashing occurs when little pieces of floc float up to the top of the clarifier due to trapped air bubbles in the floc. This is usually caused by the biological formation of H2S or N2 gas when the floc is held too long in the clarifier and runs out of O2.

      The return of well nitirified activated sludge to the primary sedimentation tank  may cause floating sludge when denitrification takes place.

      A fact that is often overlooked in primary sedimentation tank performance is affected by wastewater characteristics that occurs through sedimentation process. Larger, more slowly biodegradable SS settle first, leaving a more volatile fraction in the suspension that remains in primary tank effluent.