sewage pumping

Abstract

A method of flushing a wet well operating under a constant level pumping regime in a sewage system in which the wet well level is monitored and controlled along with the pump operation in response to a predicted period of reduced inflow. The method operates such that in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level. Independent claims are included to a control unit, a pumping station and a sewage system, which are respectively operable under the claimed method.

1 . A method of flushing a wet well operating under a constant level pumping regime in a sewage system, the method comprising the steps of:
 monitoring and controlling the wet well level and the pump operation in response to a predicted period of reduced inflow, such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level.   
   
   
       2 . A method as claimed in  claim 1  wherein the flushing method is initiated at a specific local time. 
   
   
       3 . A method as claimed in  claim 2  wherein the specific time is identified by monitoring inflow to identify periodic variations either directly or by comparison of the outputs of wet well level and pump speed monitors 
   
   
       4 . (canceled) 
   
   
       5 . A method as claimed in  claim 3  wherein the variations are identified by use of a processor or by and operator. 
   
   
       6 . (canceled) 
   
   
       7 . A method as claimed in  claim 1  wherein the flush method is initiated: once or more during each predicted period of reduced flow; once or more during alternate periods of reduced flow or any other specified fraction of periods of reduced flow; during a specified number of predicted reduced flow periods during a predetermined monitoring period; or at any other suitable frequency. 
   
   
       8 . A method as claimed in  claim 1  wherein the flushing method is initiated once during every twenty four period. 
   
   
       9 . A method as claimed in  claim 1  wherein the flush method is initiated in response to a user control; in response to a wet well level exceeding a preset level or in response to an indication that there is an increased risk of pump blockage. 
   
   
       10 . A method as claimed in  claim 1  wherein the wet well level is allowed to rise to the flush level over a rise period ahead of the predicted period of reduced inflow and the pump is controlled to allow the wet well level to either: rise substantially steadily over the whole of the rise period; or rise more rapidly during some parts of the rise period than others. 
   
   
       11 . (canceled) 
   
   
       12 . (canceled) 
   
   
       13 . A method as claimed in  claim 10  wherein the wet well level rises more slowly at the start and end of the rise period than in the middle section of the rise period. 
   
   
       14 . A method as claimed in  claim 10  wherein control of the wet well level is achieved by reducing the speed of the pump over the rise period or by stopping the pump completely for the rise period. 
   
   
       15 . A method as claimed in  claim 10  wherein the speed reduction is by a specified fraction of the normal speed and wherein the fraction is calculated with reference to a prediction of the inflow rate over this period. 
   
   
       16 . (canceled) 
   
   
       17 . (canceled) 
   
   
       18 . (canceled) 
   
   
       19 . A method as claimed in  claim 1  wherein the wet well level is reduced from the flush level to the normal level over a flush period wherein the flush period is substantially shorter than the rise period. 
   
   
       20 . A method as claimed in  claim 19  wherein the pump operates at a speed equal to or in excess of the required flow rate for self cleaning during the flush period. 
   
   
       21 . (canceled) 
   
   
       22 . A method as claimed in  claim 19  wherein the pump operates at a constant speed or at a variable speed during the flush period. 
   
   
       23 . (canceled) 
   
   
       24 . A method as claimed in  claim 10  wherein the flush period is initiated directly after the rise period; or there is a hold period between the end of the rise period and the initiation of the flush period, during which the hold period the wet well level is maintained at the flush level. 
   
   
       25 - 37 . (canceled) 
   
   
       38 . A method as claimed in  claim 1  wherein the sewage system comprises more than one pump and wherein at least some of the variations in wet well level are achieved by controlling the number of operational pumps in addition to or in place of controlling the operating speed of the pumps. 
   
   
       39 . A method as claimed in  claim 38  wherein an additional pump or pumps start operating after a predetermined time interval has elapsed since the initiation of the flush period and stop when the wet well level drops below a predetermined level. 
   
   
       40 . A method of operating a wet well using a pumping regime which comprises a plurality of modes, including: a flushing mode wherein a flushing mode comprises the steps of monitoring and controlling the wet well level and the pump operation in response to a predicted period of reduced inflow, such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level; and a default mode wherein the pumping regime is operable to control the pump operation in response to the wet well level so as to maintain the wet well level at or within a predetermined range of a desired normal level. 
   
   
       41 . A control unit for a sewage pumping station comprising:
 wet well monitoring means for monitoring the wet well level;   pump operation monitoring means for monitoring the pump operation;   a processor operable to receive input from the wet well monitoring means and pump operation means, to determine that a period of reduced inflow is predicted and to output control signals to the pump such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level.   
   
   
       42 . A control unit as claimed in  claim 41  wherein the control unit is operable in accordance with a method comprising the steps of: monitoring and controlling the wet well level and the pump operation in response to a predicted period of reduced inflow, such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level. 
   
   
       43 . A sewage pumping station incorporating a control unit comprising:
 wet well monitoring means for monitoring the wet well level;   pump operation monitoring means for monitoring the pump operation;   a processor operable to receive input from the wet well monitoring means and pump operation means, to determine that a period of reduced inflow is predicted and to output control signals to the pump such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level.   
   
   
       44 . A sewage system incorporating one or more pumping stations incorporating a control unit comprising:
 wet well monitoring means for monitoring the wet well level;   pump operation monitoring means for monitoring the pump operation;   a processor operable to receive input from the wet well monitoring means and pump operation means, to determine that a period of reduced inflow is predicted and to output control signals to the pump such that: in advance of the predicted period of reduced inflow, the wet well level is allowed to rise to a flush level; and during the predicted period of reduced inflow, the wet well level is reduced from the flush level to a normal level   wherein if the system has multiple pumping stations within it the flushing cycles of these pumping stations are coordinated to achieve maximum efficiencies of flow transfer.