Bioreactor system for multi-stage biological wastewater treatment
A bioreactor system for microbiological treatment of wastewater including: at least one highly-flexible substrate for providing a superficial environment conducive for supporting biomass growth, the substrate including: (a) a large plurality of threads disposed in a generally longitudinal direction and including a plurality of synthetic filaments, and (b) at least two cross-support elements disposed across and associated with the plurality of threads, so as to provide support for and loosely associate the threads, wherein openings defined by (i) adjacent threads of the threads, and (ii) adjacent cross-support elements of the elements, have an aspect ratio exceeding 50 to 1.
1. A method for microbiological treatment of domestic and/or industrial wastewater, comprising:
providing a plurality of successive zones in which are respectively disposed a plurality of flexible biomass-supporting substrates each comprising a plurality of threads and spaced apart cross-support elements associated with and supporting the threads, the cross-supports being disposed in angular relationship to a generally longitudinal direction in which the threads extend, said threads engaging the cross-supports and, within distance intervals between the cross-supports, having thread segments that are in loose association with one another,
providing in a plurality of substrates: a thread segment aspect ratio, which is a ratio of distances between adjacent cross-support elements relative to side-to-side or lateral distances between adjacent threads, that exceeds 50 to 1; and a length extension of the threads, which is a ratio expressed in percent, between the length of a section of substrate between adjacent cross-support elements and the average length of the threads forming that section, that is in the range of 80% to 98%,
causing wastewater to move through said zones in contact with the substrates thereof while maintaining in a succession of said zones on the substrates thereof a spatially segregated chain of trophic microorganisms distributed in succession in said zones on the loosely associated flexible biomass-supporting substrates of the respective zones,
generating gas currents in the wastewater in said zones, and causing said currents to move along the threads in said generally longitudinal direction, characterized by a linear velocity range bounded by an upper level that enables biomass to settle on said substrates, and bounded by a lower level that provides oxygen sufficient to meet an oxygen demand in said wastewater.
2. A multi-stage bioreactor system useful for microbiological treatment of domestic and/or industrial wastewater by biomass, comprising
a plurality of successive bioreactor portions, separated by walls, in which are respectively disposed a plurality of flexible biomass-supporting substrates comprising threads disposed in a generally longitudinal direction
cross-support elements disposed in angular relationship with and spaced apart from adjacent cross-supports by at least 20 cm. in said longitudinal direction, which cross-supports are associated with said plurality of threads, so as to support the threads by engaging the threads at the cross-supports while providing, within distance intervals between the cross-supports, loose association between laterally adjacent thread segments of said substrates,
wherein the biomass comprises a spatially segregated chain of trophic microorganisms distributed in succession in said portions on the loosely associated flexible biomass-supporting substrates of the respective portions,
wherein the thread segment aspect ratio, which is a ratio of distances between adjacent cross-support elements relative to side-to-side or lateral distances between adjacent threads, exceeds 200 to 1,
wherein the length extension of the threads, which is a ratio expressed in percent, between the length of a section of substrate between adjacent cross-support elements and the average length of the threads forming that section, is in the range of 80% to 98%,
a plurality of diffusing elements, fluidly connected with a source of oxygen-containing gas for treatment of the wastewater, positioned to generate rising gas currents in the wastewater and having sufficient gas discharge capacity to produce, with said rising currents, a controlled hydrodynamic circulation within said bioreactor characterized by a linear velocity range bounded by an upper level that enables biomass to settle on said substrates, and bounded by a lower level that provides oxygen sufficient to meet an oxygen demand in said bioreactor,
wherein said diffusing elements are further positioned with respect to said plurality of substrates such that a stream of oxygen-containing liquid flows down, through clearances between adjacent substrates, towards a bottom of said bioreactor, and takes part in said hydrodynamic circulation, and
wherein the substrate threads are positioned to cause the rising currents to pass along the threads in said generally longitudinal direction.