Pollution from human activities, such as fertilizer and agrochemical runoff and untreated sewage, present as great a threat to the oceans as overfishing.  Fertilizer runoff can result in nutrient overload, overgrowth of algae and bacteria that eventually result in dead zones where aquatic life cannot survive.  Harmful Algal Blooms (HABs) also produce toxins that harm humans.

Conventional agriculture results in harmful runoff.  In the nearer term, to prevent dead zones, water from conventional agriculture needs to be cleaned up of nutrients and pesticides before being released into coastal waterways.  However, commercially viable systems do not exist.  Anthropocene Institutes supports research to formulate better technology solutions.


Multi-chambered bioreactor project

Agriculture intensification has resulted in increased fertilization, and correspondingly  increased nutrient runoff.  This runoff can have disastrous effects downstream, decreasing oxygen in waters, or hypoxia, that cause much life in rivers and oceans to die. Hypoxia has been observed in Elkhorn Slough, from agriculture in Salinas, CA.

Laboratory studies have tested different materials to absorb nutrients, to clean up runoff, but the efficacy of these materials can vary with climate and nutrient type. However, small scale laboratory studies need to be vetted at pilot scale on the field, to test the efficacy of materials.  With funding from the Anthropocene Institute, Ross Clark who leads the Central Coast Wetlands Group (CCWG) operating out of Moss Landing Marine Laboratories, has put in place sensors to test levels of nutrient runoff from a multi-chambered bioreactor in a pilot scale system.

The bioreactor has 24 hour access to farm runoff where numerous materials can be tested in replicates against controls to determine efficacy, controlling temperature and flow rates and offered in an open source, user friendly database available to farmers and other stakeholders to assess the efficacy of materials on nutrient remediation.

The bioreactor assessed this past year heated vs cooled wood chips vs duckweed in cleaning up nutrient runoff. Cooled wood chips had the highest nitrogen reduction rate (45%), while heated chips and duckweed showed far less efficient, 28% and 2% respectively. The testing of other materials is already underway, comparing these rates to those of wetland channels, and algae. The CCWG will populate a materials database available via the web on the uptake curves.

Presentation slides (PDF)

Final Report


Comparison of the relative efficacies of granulated activated carbon and biochar to reduce chlorpyrifos and imidacloprid loading and toxicity using laboratory bench scale experiments. 

Pesticide loads and associated toxicity can be significantly reduced using integrated vegetated treatment systems.  The major components of these systems remove moderately soluble and hydrophobic pesticides, but they systems need a strong sorbent material to remove more soluble pesticides, such as the neonicotinoid imidacloprid.  Laboratory experiments were conducted to test the sorptive capacity of granulated activated carbon and biochar for removing imidacloprid and the organophosphate pesticide chlorpyrifos in a scaled-down treatment system.  Simulated irrigation water spiked with individual pesticides was treated with a bench-top system designed to mimic a 600 L carbon installation receiving 108,000 L of flow per day for sixteen days. Both carbon types reduced chlorpyrifos (average concentration 284 ng/L) and imidacloprid (average concentration 827 ng/L) to concentrations less than 4 ng/L and 15 ng/L for chlorpyrifos and imidacloprid, respectively.  Biochar had more efficient removal for chlorpyrifos and activated carbon had more efficient removal for imidacloprid. Biochar and activated carbon both treated environmentally relevant concentrations of pesticides in a volume of water that represented a single growing cycle for four to six typical lettuce fields (~60 acres). Results indicate that these media would likely last an entire growing season, if used properly as a post-vegetation polishing step under conditions with reduced particle loads.  

Full report here


Resources

Phytoremediation database – lists plants and algae that can absorb and break down pollutants.