Table of Contents
Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is compacted, and then starts to rise to the surface, usually as a result of denitrification, or anaerobic biological activity that produces carbon dioxide or methane.
What causes bulking sludge?
The main cause of sludge bulking is the growth of filamentous bacteria. Filamentous microorganisms grow in long strands that have much greater volume and surface area than conventional floc and are very slow to settle.
How do you control rising sludge?
To control activated sludge, you need to “have a handle” either on aeration, sludge-wasting or return-sludge flow. Aeration-rate adjustment is probably the simplest way to go. It involves, however, more than measuring aeration-basin dissolved oxygen (DO) concentration once each day.
What is a good sludge age?
The common range for sludge age for a conventional activated sludge plant is between 3 and 15 days. For extended aeration activated sludge plants the range is between about 15 and 30 days. Generally during the winter months, higher sludge ages are required to maintain a sufficient biological mass.
What methods are used to treat sludge?
Many sludges are treated using a variety of digestion techniques, the purpose of which is to reduce the amount of organic matter and the number of disease-causing microorganisms present in the solids. The most common treatment options include anaerobic digestion, aerobic digestion, and composting.
How do you determine sludge age?
The sludge age of an activated sludge process can be calculated by dividing the pounds of suspended solids or MLSS in the aeration tanks by the pounds of suspended solids that enter the aeration tanks (Equation I.
Why sludge recirculation is done in activated sludge process?
So, one reason for sludge recirculation is to control biomass distribution. And RAS flow is critical to clarifier performance. There are a couple of methods that are implemented. And this diagram shows again a clarifier with wastewater flow plus the RAS flow coming in and the RAS flow and the effluent flow going out.
How can the operator control the activated sludge process?
Return Activated Sludge By changing the RAS rate, the operator can control the concentration of organisms in the aeration tank in response to the food supply present in the incoming wastewater. This allows him to maintain the proper F/M ratio for good system performance.
How is sludge generated?
Primary sludge is generated from chemical precipitation, sedimentation, and other primary processes, whereas secondary sludge is the activated waste biomass resulting from biological treatments. Some sewage plants also receive septage or septic tank solids from household on-site wastewater treatment systems.
How does the activated sludge appear?
Activated sludge refers to a flocculent culture of organisms developed in aeration tanks under controlled conditions, according to WEF. Activated sludge is typically brown in color. Activated sludge is also known as waste activated biosolids or waste activated solids.
How do I stop sludge bulking?
Control of low F/M bulking is by reducing the aeration basin MLSS concentration and increasing the F/M (manipulating the “M” component). Lowering the MLSS concentration may not be suitable for many plants as this may cause the loss of nitrification and increase waste sludge production.
How do I find my sludge volume index?
How to calculate the SVI? Take a sample from the aeration tank. Let the sample settle for 30 minutes before analysis begins. Analyze the sample and find out the concentration of suspended solids. Divide the wet volume of the settled sludge (represented in mL/L) by the MLSS value from the last step.
What does sludge volume index indicate?
Sludge Volume Index (SVI) is an extremely useful parameter tomeasure in a wastewater treatment process. SVI gives a more accurate picture of the sludge settling characteristics than settleability or MLSS alone. SVI can indicate changes occurring in the activated sludge treatment process.
What is the name given to the sludge removed from the bottom of a secondary clarifier?
A clarifier is generally used to remove solid particulates or suspended solids from liquid for clarification and/or thickening. Concentrated impurities, discharged from the bottom of the tank are known as sludge, while the particles that float to the surface of the liquid are called scum.
How do you reduce sludge age?
The easiest and most practical way to control sludge age is with hydraulic control by wasting a defined proportion of the reactor volume daily. In AS plants with reactor concentration control, nitrification fails first.
How many types of sludge are present?
Explanation: There are two types of sludge present, primary and secondary sludge.
How do I control my MLSS in aeration tank?
The typical control band for the concentration of MLSS in wastewater is 2,000 to 4,000 mg/L for conventional activated sludge, or up to 15,000 mg/l for membrane bioreactors. One of the easiest control procedures for activated sludge systems is the Constant Mixed Liquor Suspended Solids method.
How is solid sewage sludge process?
At the POTW, the sewage passes through a series of treatment steps that use physical, biological, and chemical processes to remove nutrients and solids, break down organic materials, and destroy pathogens (disease-causing organisms) in the water.
Can sludge be used as fertilizer?
Sewage sludge is a product of wastewater treatment. Once treated, sewage sludge is then dried and added to a landfill, applied to agricultural cropland as fertilizer, or bagged with other materials and marketed as “biosolid compost” for use in agriculture and landscaping.
How do I reduce SVI in activated sludge?
Raising the amount of MLSS (reducing waste rates) changes the density of the floc, creating a heavier sludge particle. The more dense the particle, the more likely it will settle faster. The higher milligram per liter MLSS reduces the SVI result.
What are the factors affecting sludge digestion process?
Some parameters affecting the aerobic digestion process are: (1) rate of sludge oxidation, (2) sludge temperature, (3) system oxygen requirements, (4) sludge loading rate, (5) sludge age, and (6) sludge solids characteristics.
Is Rising sludge the same as bulking sludge?
Show the differences between bulking sludge and Rising sludge. Bulking Sludge Rising Sludge It is generated in the aeration tank. It is generated in secondary clarifier. Bulking sludge is caused by filamentous micro organisms. Rising sludge is caused by Denitrification.
