Method and apparatus for separating biologically digestible materials from an influent stream
A system comprising method and apparatus for separating biologically-digestible materials from an influent sewage stream. The system may comprise a primary clarification tank to capture sixty percent or more of the total solids from an influent stream; a sludge classifying press (SCP) to isolate and concentrate biologically digestible materials from sludge formed in the primary clarification tank, releasing valuable organics, such as are found in corn kernels, by fracturing the protective casings; a grit capture mechanism in a chamber within the primary clarification tank and isolated from the bulk of the sludge containing biologically-degradable materials; a grit trap to remove grit from the sludge prior to classifying the sludge with the SCP; apparatus for adding thickener to the sludge after classification and prior to digestion; and automation of one or more elements of the process for separating and digesting the biologically digestible materials in an influent stream.
1. A method for producing sludge from an influent stream of mixed biologically-digestible and non-biologically-digestible materials, comprising the steps of:
a) collecting said materials in a primary clarifier comprising a settling tank and an influent feed system;
b) first settling materials to the bottom of said clarifier to form a first sludge;
c) second settling materials to the bottom of said influent feed system to form a second sludge;
d) removing said first sludge from said settling tank;
e) classifying said first sludge to remove solids greater in size than a predetermined classification size to form a first classified sludge;
f) feeding said first classified sludge to a digester;
g) removing said second sludge from said influent feed system; and
h) separating grits and particulates from said second sludge to form a substantially grit-free second sludge.
2. A method in accordance with claim 1 further comprising the steps of:
a) classifying said substantially grit-free second sludge by removing solids greater in size than a predetermined classification size to form a second classified sludge; and
b) feeding said second classified sludge to said digester.
3. A method in accordance with claim 2 wherein said classifying step further comprises a step selected from the group of steps consisting of compressing and sheering said substantially grit-free sludge to release biologically-digestible materials from solids greater in size than said classification size.
4. A method in accordance with claim 3 wherein said classification size is 1.6 mm.
5. A method in accordance with claim 2 comprising the further step of adding flocculants to at least one of said first and second classified sludges.
6. A method in accordance with claim 2 comprising the further step of thickening said classified sludge prior to feeding said classified sludge to said digester.
7. A method in accordance with claim 2 further comprising the step of thickening said classified sludge to increase the total solids content of said second classified sludge to at least 5% total solids.
8. A method in accordance with claim 1 wherein a rate at which said substantially grit-free sludge is classified is based upon measurement of at least one characteristic of said classified sludge.
9. A method in accordance with claim 1 wherein said adding step is carried out at a rate based upon a measurement of at least one characteristic of said classified sludge.
10. A method in accordance with claim 9 wherein said characteristic is selected from the group consisting of solids content, UVAS, and turbidity.
11. A method in accordance with claim 1 wherein said feeding step is carried out at a rate based upon measurement of at least one characteristic of bio-gases produced by digestion of said classified sludge.