The disclosure describes an algal system for improving water quality through the use of algae. In example embodiments, the algal system comprises an elongate device including algae enclosed therein and capable of reducing at least the levels of nitrates and phosphates in water directed through the device. The algae may be capable of also reducing E. coli bacteria, other bacteria, and viruses in the water. Preferably, the algae comprises a filamentous green algae, including without limitation, Spirogyra grevilleana algae. In one example embodiment, the algal system comprises an elongate device and an elongate cartridge that is pre-configured to treat certain chemical compounds, bacteria, and viruses, and certain other characteristics of water. The cartridge is delivered to the site where the water is to be treated and installed in the field, possibly replacing an existing cartridge. After use, algae may be processed into biofuel.
