Wastewater treatment system

Abstract

A system for treating a wastewater stream produces an effluent having an acceptable level of turbidity. A PID controller is operatively coupled to at least one turbidity meter for monitoring turbidity of the effluent stream. A plurality of chemical treatment additive pumps are provided for adding a plurality of treatment chemicals to the wastewater stream in real time under supervision of the controller, and responsive to monitored turbidity.

1 . A method for treating a wastewater stream to produce an effluent stream, the method comprising:
 supplying, by a pump, a chemical additive to the wastewater stream at a variable flow rate;   continuously measuring, by a sensor disposed within the wastewater stream, clarity of the wastewater stream;   continuously measuring, by a flow meter disposed within the wastewater stream, flow of the wastewater stream;   varying, by a controller, the variable flow rate of the chemical additive based on clarity measurements generated by the sensor and flow measurements generated by the flow meter; and   maintaining the clarity of the effluent stream within a specified range by continually injecting, by the pump, the chemical additive into the wastewater stream in real time in response to adjustments specified by the controller.   
     
     
         2 . The method of  claim 1 , wherein the controller is selected from:
 a programmable logic controller (PLC); and   a proportional-integral-derivative (PID) controller.   
     
     
         3 . The method of  claim 1 , wherein the sensor is selected from:
 a biological oxygen demand (BOD) sensor;   a chemical oxygen demand (COD) sensor;   a conductivity sensor;   a potential of hydrogen (pH) sensor;   a total suspended solids (TSS) sensor; and   a turbidity sensor.   
     
     
         4 . The method of  claim 1 , further comprising:
 supplying, by a coagulant pump, a coagulant to the wastewater stream at a first variable flow rate; and   supplying, by a polymer pump, a polymer to the wastewater stream at a second variable flow rate.   
     
     
         5 . The method of  claim 1 , further comprising:
 continuously measuring, by a second sensor disposed within the effluent stream, clarity of the effluent stream.   
     
     
         6 . The method of  claim 5 , further comprising:
 operatively coupling an output of the second sensor representative of effluent clarity to an input of the controller,   wherein the controller is configured to change the chemical dosing in response to determining that the output exceeds a specified threshold.   
     
     
         7 . The method of  claim 1 , wherein the sensor is disposed downstream of a plurality of flocculent tubes. 
     
     
         8 . The method of  claim 1 , wherein the sensor is a pH sensor in fluid communication with the wastewater stream having an output representative of pH of the wastewater stream that is operatively coupled to an input of the controller. 
     
     
         9 . The method of  claim 8 , further comprising:
 supplying, by a pH additive delivery pump, an acidic solution or an alkaline solution to the wastewater stream based on the output of the pH sensor.   
     
     
         10 . The method of  claim 1 , wherein the sensor is connected to an automatic cleaning system that includes
 a clean water source, and   a chemical addition system on a timer that interfaces with the controller.   
     
     
         11 . The method of  claim 1 , further comprising:
 setting the controller to meet a performance objective, a costing objective, or a combination of performance and costing objectives.   
     
     
         12 . The method of  claim 11 , wherein the controller is set to ensure an acceptable level of chemical over-shooting where compliance is required. 
     
     
         13 . The method of  claim 11 , wherein the controller is set to minimize chemical over-shooting where cost efficiency is required. 
     
     
         14 . A method for treating a wastewater stream to produce an effluent stream, the method comprising:
 producing a flow rate value by continually measuring flow rate of the wastewater stream;   producing a clarity value by continually measuring clarity of the wastewater stream by sampling directly from the wastewater stream;   determining an appropriate chemical additive flow rate needed to achieve a specified effluent quality level based on the flow rate value and the clarity value;   outputting a chemical additive flow rate signal to a pump that specifies an amount of chemical additive to be injected into the wastewater stream;   continually monitoring the flow rate value and the clarity value in real time to determine whether an adjustment to the amount of chemical additive is needed to maintain clarity of the effluent stream at a substantially steady level after reaching the specified effluent quality level; and   causing the pump to inject the amount of chemical additive into the wastewater stream.   
     
     
         15 . The method of  claim 14 , further comprising:
 producing a second clarity value by continually measuring clarity of the effluent stream by sampling directly from the effluent stream.   
     
     
         16 . The method of  claim 15 , wherein a first sensor produces the clarity value and a second sensor produces the second clarity value. 
     
     
         17 . The method of  claim 16 , wherein a controller determines the appropriate chemical additive flow rate needed to achieve the specified effluent quality level. 
     
     
         18 . The method of  claim 17 , wherein an output of the second sensor representative of effluent clarity is operatively coupled to an input of the controller, and wherein the controller adjusts the amount of chemical additive in response to determining the output exceeds a specified threshold. 
     
     
         19 . A system for treating a wastewater stream to produce an effluent stream, the system comprising:
 a pump configured to inject a chemical additive into the wastewater stream at a variable flow rate;   a sensor, disposed within the wastewater stream, configured to continuously measure clarity of the wastewater stream;   a flow meter, disposed within the wastewater stream, configured to continuously measure flow rate of the wastewater stream; and   a controller configured to
 determine an appropriate chemical additive flow rate needed to achieve a specified effluent quality level based on the clarity and the flow rate, 
 output a chemical additive flow rate signal to the pump that specifies an amount of chemical additive to be injected into the wastewater stream, and 
 monitor the clarity and the flow rate in real time to determine whether an adjustment to the amount of chemical additive is needed to maintain clarity of the effluent stream at a substantially steady level after reaching the specified effluent quality level. 
   
     
     
         20 . The system of  claim 19 , wherein the controller is selected from:
 a programmable logic controller (PLC); and   a proportional-integral-derivative (PID) controller.   
     
     
         21 . The system of  claim 19 , wherein the pump is one of a plurality of pumps that are operatively coupled to the controller, and wherein each pump of the plurality of pumps is associated with a different chemical additive. 
     
     
         22 . The system of  claim 21 , wherein the controller is configured to output a distinct flow rate signal to each pump of the plurality of pumps, and wherein each distinct flow rate signal is adjusted in real time based on the clarity and the flow rate.