Activated Sludge: Bulking and Foaming Control
Control methods, based on the specific type s of filaments causing the problem, follow. In this second part, physical and chemical filament control and the causes of activated sludge foaming and its control are presented. There are many cross-references in the text which will lead the reader to the background of the problem, and to show its connection to similar problems and their solutions. Thiothrix I and II , Beggiatoa spp. Inappropriate selector use may made the problem worse for example, where bulking is caused by low DO, nutrient deficiency or waste septicity.
Activated Sludge: Bulking and Foaming Control
Selector design is empirical at this time. The best approach is to try several selector sizes, using a larger basin or channel with movable baffles or exit gates. In systems treating mixed domestic and industrial wastes, only TIN and ortho-phosphorus should be used to calculate nutrient availability. We provide complimentary e-inspection copies of primary textbooks to instructors considering our books for course adoption. If the selector is too large, the substrate concentration achieved may not be high enough to encourage these special floc-formers and discourage filaments. Naturally, the practical pieces of information required for solving practical operational problems are more stressed.
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If the selector is too large, the substrate concentration achieved may not be high enough to encourage these special floc-formers and discourage filaments. If too small, insufficient time may be available for substrate uptake and storage. Also, a selector that is too small may cause the floc-formers to shunt carbonaceous substrate to exocellular polymer which can increase the SVI of the sludge "slime bulking" and pose problems in waste sludge dewatering.
The best approach is to try several selector sizes, using a larger basin or channel with movable baffles or exit gates.
Use of a variable wastewater bypass around the selector can achieve the same objective and allow the operator some control over the selector. Inappropriate selector use may made the problem worse for example, where bulking is caused by low DO, nutrient deficiency or waste septicity. Influent wastewater septicity is usually indicated by odors H2S or "rotten egg" smell and a dark color to the wastewater, caused by precipitated ferric sulfide.
Septic wastes contain elevated amounts of sulfides and low molecular weight organic acids such as acetic and butyric acids , both of which encourage the growth of certain filaments see Table 1. Observation of these filaments with intracellular sulfur granules is a tip-off of a septicity problem.
Septicity is more common in systems in warmer climates and in those with large wastewater collection systems that have lift stations and force mains. Waste septicity can be treated by preaeration which releases odors , by chemical oxidation chlorine, hydrogen peroxide or potassium permanganate , by chemical precipitation ferric chloride , or use of sodium nitrate in the collection system as an "oxygen source".
Septicity can originate within plant processes. Common sources of septicity include equalization basins, primary and secondary clarifiers, and return streams from sludge processing. These can be tested for sulfide or organic acid concentration to determine whether they are a significant source of septicity.
Sulfide can be tested for using one of the simple sulfide test kits available commercially such as by HACH. Organic acids can be tested for using distillation and titration as per Standard Methods the same test as for digesters. Nitrogen and phosphorus can be growth limiting if not present in sufficient amounts in influent wastewater, a problem with industrial wastes and not domestic wastes. In general, a BOD5: P weight ratio in the wastewater of Other nutrients such as iron or sulfur have been reported as limiting to activated sludge, but this is not common.
Signs of nutrient deficiency include: One check for nutrient deficiency is to be sure that at least 1. In systems treating mixed domestic and industrial wastes, only TIN and ortho-phosphorus should be used to calculate nutrient availability. Organically combined nitrogen and phosphorus Kjeldahl nitrogen and total phosphorus may not be hydrolyzed fast enough by the microorganisms in the activated sludge to keep pace with BOD use.
The aeration basin pH should be maintained in the range 6. The aeration basin pH can be adjusted using caustic, lime or magnesium hydroxide. Control methods for filamentous bulking are based on, first, confirmation that the problem is indeed caused by filaments some are not and, second, identification of the causative filament s. This information leads to specific remedies that can be used, appropriate for the filament s involved.
In this second part, physical and chemical filament control and the causes of activated sludge foaming and its control are presented. There exist several methods of chemical addition to enhance activated sludge settling. Most used are synthetic, high molecular weight, cationic polymers alone or in combination with an anionic polymer that serve to overcome the physical effects of filaments on sludge settling.
These are usually added to the MLSS as it leaves the aeration basin or to the secondary clarifier centerwell. A polymer supply company should be consulted for selection of a polymer. Jar testing should be performed at your plant to determine the type of polymer needed and its dosage, which are quite plant specific.
These produce a voluminous precipitate that sweeps down the activated sludge, improving settling. Sludge production may be significantly increased if these are used.
The weighting action of inert biological solids has also been used to aid sludge settling in activated sludge modifications such as the Hatfield or Kraus processes that recirculate anaerobic digester contents through the aeration basin.
Clay and fiber addition have been used by some industries e. Two toxicants, chlorine and hydrogen peroxide, have been used successfully to control filaments.
Chlorine is the most widely used as it is relatively inexpensive and available on-site at most plants, and only this will be discussed here. The goal of chlorination is to expose the activated sludge to sufficient chlorine to damage filaments extending from the floc surface while leaving organisms within the floc largely untouched.
Bulking and Foaming Control. Add to Wish List. Toggle navigation Additional Book Information. Description Table of Contents. Features Major guide to control of bulking and foaming in sludge. Practical control measures combine both microbiological and engineering approaches.
Based on over 25 years of research and direct practical experience from lab-scale to full-scale operations. Summary Filamentous bulking and foaming are the most frequent operational problems in activated sludge plants. This recent book provides a comprehensive, concise guide to the microbiological and technical aspects of bulking and foaming control.
Iamges: bulking and foaming
All articles with unsourced statements Articles with unsourced statements from March All stub articles. Lee and Shun Dar Lin Description Table of Contents.
The result of over 25 years of research, the book stresses practical control measures based on kinetic and metabolic selection theories, as well as on case histories.
Chlorine dose is measured conveniently on the basis of sludge inventory in bulking and foaming trenbolone kullan?m? overall chlorine mass dose. Popular passages Page - Davidson, Bulking and foaming This information leads to specific remedies, appropriate for the filament s involved. Offline Computer — Download Bookshelf software to your desktop so you can view your eBooks with or without Internet access. Shop for Books on Google Play Browse the world's largest eBookstore and start reading today on the web, tablet, phone, or ereader.
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