Advanced Biologic Water Treatment Using Algae

Abstract

An advanced water treatment method processes a continuous flow of water in a sequence of stages including pre-filtering [ 200 ] to remove solids, conditioning [ 202 ] to adjust pH, blending [ 210 ] with a recycled dense microalgae culture, and passing the resulting mixture through an enclosed, environmentally-controlled photobioreactor [ 212 ] where nutrients, PCB's, trace metals and other pollutants and regulated compounds are taken up by the algae. The flow from the PBR is separated using cross-flow filtration [ 222 ] to produce a treated water flow and a dense microalgae flow that is recycled to the blending stage [ 210 ] upstream. Thus, whereas the algae is recycled, the water entering the system is treated by flowing sequentially through the stages of the system, without any recycling or repetition of treatment stages. A pig-type cleaning system is also provided.

1 . A method for advanced water treatment, the method comprising:
 a) receiving a continuous flow of water;   b) pre-filtering the received flow of water to reduce suspended solids;   c) conditioning the pre-filtered flow of water to increase bio-availability of nutrient constituents in the pre-filtered flow;   d) blending in a blending vessel the conditioned flow with a dense live microalgae flow (RAA) to produce a mixture flow;   e) passing the mixture flow once through an enclosed tube photobioreactor (PBR) so that microalgae in the mixture flow reproduce and take up nutrients and trace metals in the mixture flow;   f) continuously separating microalgae from the mixture flow exiting the photobioreactor to produce a treated flow (permeate) and the dense live microalgae flow (RAA);   g) continuously returning the dense live microalgae flow (RAA) to the blending vessel; and   h) periodically circulating a cleaning body (pig) through the PBR, wherein the pig comprises a first component and a second component tethered to each other.   
     
     
         2 . The method of  claim 1  wherein periodically circulating the pig through the PBR comprises launching the pig from a pig by-pass tube into the PBR, circulating the pig with the mixture flow through the PBR, and retrieving the pig from the PBR into the pig by-pass tube upstream from the blending vessel. 
     
     
         3 . The method of  claim 1  wherein periodically circulating the pig through the PBR comprises detecting the arrival of the pig in the pig by-pass tube, closing a first valve in the pig by-pass tube to capture the pig, opening a second valve in the pig by-pass tube to launch the pig, and after launching the pig opening the first valve and closing the second valve. 
     
     
         4 . The method of  claim 3  wherein closing and opening the first valve and second valve is performed automatically by a monitoring and control system connected to the first valve and second valve. 
     
     
         5 . The method of  claim 3  wherein closing and opening the first valve and second valve is performed manually. 
     
     
         6 . The method of  claim 3  wherein detecting the arrival of the pig in the pig by-pass tube is performed using a proximity sensor connected to a monitoring and control system. 
     
     
         7 . The method of  claim 1  wherein the first component comprises a magnet, a radiofrequency identification (RFID) tag, radioactive tracer, or ultrasonic transmitter. 
     
     
         8 . The method of  claim 1  wherein the first component is coated with rubber, silicone, or polymer. 
     
     
         9 . The method of  claim 1  wherein the first component comprises a layer of metallic tape coated with rubber. 
     
     
         10 . The method of  claim 1  wherein the first component and second component are tethered with a flexible cable. 
     
     
         11 . The method of  claim 1  wherein the first component and second component are tethered to each other with a ball and socket joint. 
     
     
         12 . The method of  claim 1  wherein the first component has a mass greater than a mass of the second component. 
     
     
         13 . The method of  claim 1  wherein the second component comprises a brush. 
     
     
         14 . The method of  claim 1  wherein the first component has a hemispherical shaped surface and wherein the first component is tethered at a position opposite the hemispherical surface. 
     
     
         14 . The method of  claim 14  wherein the first component has a spherical shaped surface. 
     
     
         15 . The method of  claim 14  wherein the first component has a teardrop shaped surface. 
     
     
         16 . The method of  claim 14  wherein the first component has an ellipsoidal shaped surface.