Photobioreactor

Abstract

A photobioreactor for growing algae comprises a tank for holding a volume of growth medium. A plurality of light sources are disposed either within the tank or externally to it in a manner to illuminate substantially uniformly the entire volume of growth medium when the tank is in operation. At least one draft tube is disposed within the tank, above the floor or bottom of the tank, and a diffuser for diffusing a gas stream is disposed near the bottom of the tank so that gas bubbles released from the diffuser rise to the surface of the liquid within the draft tube, thus causing fluid flow upward within the draft tube and downward outside of it, imparting a mixing or agitating motion to algae strains growing within the tank.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 280,847, filed Nov. 10, 2009, entitled Method for Algal Treatment of Effluent from an Anaerobic Digester and Creation of Useful Algal Biomass, which is incorporated herein for all purposes.FIELD OF THE INVENTION[0002]The present invention relates generally to wastewater treatment systems and methods, and more particularly relates to wastewater treatment systems utilizing anaerobic and aerobic microorganisms for bioremediation.BACKGROUND OF THE INVENTION[0003]The vast majority of the world's wastewater does not undergo treatment of any kind before being dumped into the nearest open water source. This has resulted in an international health crisis, where people die daily for lack of clean water. Unstable ecosystems caused by nutrient rich waste runoff are creating high rates of fish kill, ocean floor plant kill and large concentrations of pathogenic bacteria. This is a dire...

AI Technical Summary

Benefits of technology

"The present invention provides a system and method for efficient and cost-effective bioremediation of wastewater and other contaminated fluid streams. The invention includes a photobioreactor for growing high concentrations of algae, a nutrient system for supplying nutrients to the photobioreactor, and a remediation pond for receiving the effluent from the photobioreactor and further processing it. The invention also includes various components and methods for optimizing the growth of algae, such as using light pipes and multiple draft tubes. The overall system and method can effectively remove residual nitrogen, phosphorus, and CO2 from the effluent of anaerobic digestion."

Problems solved by technology

This has resulted in an international health crisis, where people die daily for lack of clean water.

Unstable ecosystems caused by nutrient rich waste runoff are creating high rates of fish kill, ocean floor plant kill and large concentrations of pathogenic bacteria.

This is a direct effect of lack of treatment or poor treatment and disposal of such waste streams.

Effects such as disastrous algae blooms in open water sources from eutrophic conditions have drastically increased in the past decade and pose unprecedented environmental problems.

These systems are expensive to build and to operate, not solely because of the high energy costs incurred in the aeration process, but also because of the manpower required to operate the expensive machinery employed in such systems.

Such mechanical / chemical treatment facilities, even those that are considered “state of the art,” have a price tag in the millions and even up to hundreds of millions of dollars, making them so expensive that many communities, in the US and other parts of the developed world, have in the past been unable to afford such sewage treatment systems.

As a result, the majority of the world's population lives with massive sewage pollution.

Because these prior art systems do not have a mechanism for controlling the algal specie(s) present, their algae cultures drift over time, often with unwanted outcomes.

These undesirable outcomes include the growth of species that cannot be easily separated from the water at the end of processing; the proliferation of species that grow well during “normal” conditions, but are unable to grow in the case of process excursions, e.g. an influx of an industrial pollutant; or the proliferation of algaie species that grow well, but do not perform all of the desired remediation.

Further, absent a mechanism for active replenishment of the algae, wash-out events (e.g. from a rainstorm) can severely dilute the algae culture density, such that the system is unacceptably slow to return to an effective culture density.

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