Method for wastewater treatment with resource recovery and reduced residual solids generation

1. A process for treating wastewater comprising the steps of:

wasting volume fraction of organic cell mass form an aerobic membrane bioreactor to an anaerobic digester system; and

maintaining a solids retention time (SRT) in the bioreactor that is (1) greater than a time needed to achieve growth of organisms suitable for converting carbonaceous biochemical oxygen demand (CBOD) into cell mass and (2) less than a time at which substantial decay of the organisms occurs;

wherein the step of wasting from the aerobic membrane bioreactor to the anaerobic digester system is intermittent or discontinuous.

2. A process for treating wastewater comprising the steps of:

wasting a volume fraction of organic cell mass from an aerobic membrane bioreactor to an anaerobic digester system; and

maintaining a solids retention time (SRT) in the bioreactor that is (1) greater than a time needed to achieve growth of organisms suitable for converting carbonaceous biochemical oxygen demand (CBOD) into cell mass and (2) less than a time at which substantial decay of the organisms occurs;

further comprising the step of filtering activated sludge from the aerobic membrane bioreactor in a membrane separator external to the membrane bioreactor.

3. A process for treating wastewater comprising the steps of:

wasting a volume fraction of organic cell mas from an aerobic membrane bioreactor to an anaerobic digester system; and

maintaining a solids retention time(SRT) in the bioreactor that is (1) greater than a time needed to achieve growth of organisms suitable for converting carbonaceous biochemical oxygen demand (CBOD) into cell mass and (2) less than a time a which substantial decay of the organisms occurs;

further comprising the steps of removing and recovering phosphorus from the wastewater.

4. A process for treating wastewater comprising the steps of: wasting a volume fraction of organic cell mass from an aerobic membrane bioreactor to an anaerobic digester system; and

maintaining a solids retention time (SRT) in the bioreactor that is (1) greater than a time needed to achieve growth of organisms suitable for converting carbonaceous biochemical oxygen demand (CBOD) into cell mass and (2) less than a time at which substantial decay of the organisms occurs;

further comprising the steps of removing and recovering ammonia from the wastewater.

5. A process for treating wastewater comprising the steps of:

wasting a volume fraction of organic cell mass from an aerobic membrane bioreactor to an anaerobic digester systems; and

maintaining a solids retention time (SRT) in the bioreactor that is (1) greater than a time needed to achieve growth of organisms suitable for converting carbonaceous biochemical oxygen demand (CBOD) into cell mass and (2) less than a time at which substantial decay of the organisms occur;

further comprising pretreating the wastewater prior to being introduced into the membrane bioreactor.

6. The process of claim 1 , 2 , 3 , 4 , or 5 , wherein the step of maintaining the SRT includes controlling the SRT in a range between about 1 to about 3 days.

7. The process of claim 1 , 2 , 3 , 4 , or 5 , further comprising the step of controlling a minimum dissolved oxygen concentration in the aerobic membrane bioreactor of at least about 0.5 mg/l.

8. The process of claim 1 , 2 , 3 , 4 , or 5 , wherein the step of maintaining a SRT includes maintaining the SRT to minimize ammonia oxidation in the aerobic membrane bioreactor.

9. The process of claim 1 , 2 , 3 , 4 , or 5 , further comprising the step of operating the aerobic membrane bioreactor at a volatile suspended solids concentration (VSS) of least about 7 g/l and a corresponding total suspended solids (TSS) concentration of at least about 8 g/l.

10. The process of claim 1 , 2 , 3 , 4 , or 5 , further comprising the step of controlling a temperature of the anaerobic digester system in a range of between about 30 to about 35° C.

11. The process of claim 2 , 3 , 4 , or 5 , wherein the step of wasting from the aerobic membrane bioreactor to the anaerobic digester system is continuous.

12. The process of claim 1 , 2 , 3 , 4 , or 5 , wherein the step of wasting is directly from the aerobic membrane bioreactor to an anaerobic digester of the anaerobic digester system.

13. The process of claim 1 , 2 , 3 , 4 , or 5 , wherein the step of wasting is indirectly from the aerobic membrane bioreactor to an anaerobic digester of the anaerobic digester system.

14. The process of claim 1 , 3 , 4 , or 5 , further comprising the step of filtering activated sludge from the aerobic membrane bioreactor in a membrane separator submerged in mixed-liquor contents of the membrane bioreactor.

15. The process of claim 1 , 2 , 4 , or 5 , further comprising the steps of removing phosphorus from the wastewater.

16. The process of claim 3 further comprising the step of returning a backwash formed in the removing and recovering phosphorus steps to the membrane bioreactor.

17. The process of claim 5 further comprising pretreating the waste water with a screen or grit remover.

18. The process of claim 1 , 2 , 3 , 4 , or 5 , further comprising filtering the wastewater prior to being introduced into the membrane bioreactor with a high performance primary treatment filter system.

19. The process of claim 1 , 2 , 3 , 4 , or 5 , further comprising pretreating the wastewater with a screen or grit remover and filtering the wastewater with a high performance primary treatment filter system prior to the wastewater being introduced into the membrane bioreactor.