Infiltration/inflow control for membrane bioreactor

1. A wastewater treatment system comprising:

a plurality of treatment zones including an upstream treatment zone in fluid communication with one or more downstream treatment zones;

a membrane module in fluid communication downstream of the upstream treatment zone and the one or more downstream treatment zones, the membrane module comprising a filter membrane;

a gravity-settling device in fluid communication downstream of the upstream treatment zone and upstream of the one or more downstream treatment zones;

a weir positioned between the upstream treatment zone and the gravity settling device and configured to provide a flow of liquid between the upstream treatment zone and the gravity settling device responsive to a flow of wastewater into the wastewater treatment system exceeding an average design flow rate and to block the flow of liquid between the upstream treatment zone and the gravity settling device responsive to the flow of wastewater into the wastewater treatment system not exceeding the average design flow rate;

wherein a height of the weir is automatically adjustable based on a measurement of a process variable of the wastewater treatment system.

2. The wastewater treatment system of claim 1 , further comprising one or more pumps operable in response to a liquid level in the upstream treatment zone to control a flow of liquid between the plurality of treatment zones and the filter membrane.

3. The wastewater treatment system of claim 1 , wherein a flow of liquid between the plurality of treatment zones and the filter membrane is controlled by the weir.

4. A wastewater treatment system comprising:

a plurality of treatment zones including an upstream treatment zone in fluid communication with one or more downstream treatment zones;

a membrane module in fluid communication downstream of the upstream treatment zone and the one or more downstream treatment zones, the membrane module comprising a filter membrane;

a control means configured to control a ratio between an amount of a mixed liquor from the filter membrane which is returned to the upstream treatment zone and an amount of mixed liquor from the filter membrane which is returned to the one or more downstream treatment zones;

a gravity-settling device in fluid communication downstream of the upstream treatment zone and in fluid communication upstream of the one or more downstream treatment zones; and

a flow control device positioned between the upstream treatment zone and the gravity settling device and configured to provide a flow of liquid between the upstream treatment zone and the gravity settling device responsive to a flow of wastewater into the wastewater treatment system exceeding an average design flow rate and to block the flow of liquid between the upstream treatment zone and the gravity settling device responsive to the flow of wastewater into the wastewater treatment system not exceeding the average design flow rate.

5. The wastewater treatment system of claim 4 , wherein the control means is configured to control the ratio based on a total flow of wastewater being treated by the gravity-settling device.

6. The wastewater treatment system of claim 5 , further comprising a programmable control device configured to control an amount of mixed liquor from the membrane filter which is sent to the gravity-settling using a mass balance equation to determine the ratio required to maintain a required mixed liquor suspended solids concentration in a liquid flow being transferred to the gravity-settling device.

7. The wastewater treatment system of claim 6 , wherein the mass balance equation includes variables comprising one or more of:

an average total suspended solids concentration in the mixed liquor;

a desired mixed liquor suspended solids concentration in the furthest upstream treatment zone;

a total influent wastewater flow; and

a percentage of the total influent wastewater flow being treated by the gravity settling device.

8. A wastewater treatment system comprising:

a plurality of treatment zones including an upstream treatment zone in fluid communication with one or more downstream treatment zones;

a membrane module in fluid communication downstream of the upstream treatment zone and the one or more downstream treatment zones, the membrane module comprising a filter membrane;

a gravity-settling device in fluid communication downstream of the upstream treatment zone and in fluid communication upstream of the one or more downstream treatment zones;

a flow control device positioned between the upstream treatment zone and the gravity settling device and configured to provide a flow of liquid between the upstream treatment zone and the gravity settling device responsive to a flow of wastewater into the wastewater treatment system exceeding an average design flow rate and to block the flow of liquid between the upstream treatment zone and the gravity settling device responsive to the flow of wastewater into the wastewater treatment system not exceeding the average design flow rate; and

an outflow line for returning sludge separated from a mixed liquor in the gravity settling device to one of the plurality of downstream treatment zones.

9. The wastewater treatment system of claim 8 , further comprising a pretreatment unit.

10. The wastewater treatment system of claim 8 , wherein the plurality of treatment zones comprises an aeration system.

11. The wastewater treatment system of claim 8 , further comprising an equalization tank in fluid communication with at least one of the plurality of treatment zones.

12. The wastewater treatment system of claim 8 , further comprising a reserve storage tank in fluid communication with at least one of the plurality of treatment zones.