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.

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) measuring a flow velocity of the mixture flow and automatically adjusting the mixture flow to maintain stable mixture levels in the blending vessel and filter equalization tank.   
     
     
         2 . The method of  claim 1  further comprising
 measuring pH levels of the prefiltered flow and automatically adding CO 2  to the pretreated flow based on the measured pH levels to maintain a measured pH level between 6.5 and 7.4. 
 
     
     
         3 . The method of  claim 1  further comprising
 measuring an ambient light level near the photobioreactor and exposing the photobioreactor to supplemental light if the ambient light level is below 80 PAR. 
 
     
     
         4 . The method of  claim 3  wherein exposing the photobioreactor to supplemental light comprises activating red LED lights. 
     
     
         5 . The method of  claim 3  further comprising
 terminating exposure of the photobioreactor to the supplemental light if the measured ambient light level remains above 400 PAR for 20 minutes. 
 
     
     
         6 . The method of  claim 1  further comprising
 aggregating and storing measured system operational data and performing an historical trend analysis. 
 
     
     
         7 . The method of  claim 6  wherein the system operational data comprises effluent flows, pH levels, and discharge levels. 
     
     
         8 . 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) automatically entering a backwash mode by opening and closing valves to create a backwash flow through a microalgae separation filter, and when the backwash mode is completed returning the valves to normal operating states.   
     
     
         9 . 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) switching into a recirculation mode, wherein the switching comprises stopping the separation of microalgae from the mixture flow, recirculating the mixture flow to the blending vessel, and stopping the conditioned flow from entering the blending vessel.   
     
     
         10 . The method of  claim 9  further comprising
 switching into recirculation mode when a sensed quality of the mixture flow departs from a predetermined range.