Method and apparatus for wastewater treatment using screens
AssigneeD.C. Water & Sewer Authority
InventorsSudhir N. Murthy, Eugenio Giraldo, Norman D. Dockett, Walter F. Bailey
Life of this patent
Estimating the term…
Abstract
An apparatus and method for selecting and retaining solids in an activated sludge process for the improving wastewater treatment using screens. The screens can be used to separate and retain solids based on size or compressibility. The screens are used to separate and select for slow growing organisms, faster settling organisms, or materials added to absorb, treat or remove constituents in the activated sludge process.
Claims23
A system for treating wastewater, said system comprising:
- a bioreactor for treating the wastewater according to an activated sludge process;
- and
- a classifying screen for selectively screening material from mixed liquor or sludge, wherein the selection occurs based on resistance to compression or shear, where a fraction of the mixed liquor or sludge that is more resistant to compression or shear is retained, such that the fraction of the mixed liquor or sludge that is more resistant to compression or shear does not pass through the classifying screen, while a fraction of the mixed liquor or sludge that is less resistant to compression or shear passes through the classifying screen;
- and
- wherein the screening apparatus is configured to transmit the fraction of the mixed liquor or sludge that is more resistant to compression or shear, which fraction does not pass through the classifying screen and is thereby retained by the classifying screen, from the classifying screen to a portion of the bioreactor that is upstream from the classifying screen.
A method for separating two or more solids fractions from mixed liquor, to maintain two or more solids residence times, the method comprising:
- providing the mixed liquor;
- providing classifying screens within said mixed liquor;
- preferentially selecting said fractions with a solids retention time higher than a desired threshold using said classifying screens;
- and
- maintaining said fractions with a lower solids retention time by pass through or by using any other solid liquid separator;
- wherein the solids retention times of the selected solids can be adjusted and requires a swapping of classifying screens size and/or solid-liquid separator for the higher and/or lower solids retention times respectively.
A method for separating two or more solids fractions from mixed liquor, to maintain two or more solids residence times, the method comprising:
- providing the mixed liquor;
- providing classifying screens within said mixed liquor;
- preferentially selecting said fractions with a solids retention time higher than a desired threshold using said classifying screens;
- and
- maintaining said fractions with a lower solids retention time using any other solid liquid separator;
- wherein the preferential selection occurs based on resistance to compression or shear, where a fraction that is more resistant to compression or shear is retained.
Dependencies are inferred from the claim text.