Event Title

Silicate Cycling in Wastewater Diatoms

Mentor 1

John Berges

Mentor 2

Erica Young

Location

Union Wisconsin Room

Start Date

24-4-2015 10:30 AM

End Date

24-4-2015 11:45 AM

Description

Algae are recognized as good sources of material for biofuel including cellulose (for ethanol production) and lipids (useful for biodiesel synthesis). In the course of a previous project aimed at growing the green alga Cladophora spp., in secondarily-treated wastewaters to remove nutrients, it was recognized that the Cladophora (rich in cellulose) accumulated large amounts of epiphytic diatoms (rich in lipids). Thus, algae grown in wastewater potentially represent superior material for biofuel. However, diatoms require the nutrient silicate in addition to nitrogen and phosphorus found in wastewater, and silicate concentrations, fluxes, and cycling have never been studied under such conditions. A mathematical model (we previously developed for benthic lake environments) based on a system of ordinary differential equations to predict the proportional growth and decay of silicate pools within a closed system, was re-parameterized for wastewater conditions and solved (using MATLAB). The pilot treatment system (at the Jones Island Wastewater Treatment Plant Milwaukee, WI), consisted of troughs (4 troughs, each approximately 0.5 x 3.0 x 1.5 m) in which secondary-treated domestic wastewater flowed over naturally-growing alga. Weekly measurements were made of the pools of silicate (i.e. dissolved and particulate biogenic silicate) by measuring water flowing into and out of troughs, and the material in the troughs. Inflow of dissolved silicate ranged from 12-111 uM, outflow of dissolved silicate ranged from 12-98 uM, inflow of particulate biogenic silicate ranged from 0.11-7.4 uM, and outflow particulate biogenic silicate ranged from 0.1-28 uM. Biomass of silica in the Cladophora/diatom assemblage- averaged 229 uM Si/g dry mass. First attempts at parameterizing the model used the proportional relationship between inflow and outflow concentrations, but large fluctuations in biomass invalidated steady-state assumptions. Currently, we are re-structuring the models into an open system and re-tuning parameter values. Ultimately our goal is to make predictions about rates of silicate cycling under different flow rates and nutrient concentrations in order to determine the optimal conditions, or algal biomass and thus-lipid and cellulose production.

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Apr 24th, 10:30 AM Apr 24th, 11:45 AM

Silicate Cycling in Wastewater Diatoms

Union Wisconsin Room

Algae are recognized as good sources of material for biofuel including cellulose (for ethanol production) and lipids (useful for biodiesel synthesis). In the course of a previous project aimed at growing the green alga Cladophora spp., in secondarily-treated wastewaters to remove nutrients, it was recognized that the Cladophora (rich in cellulose) accumulated large amounts of epiphytic diatoms (rich in lipids). Thus, algae grown in wastewater potentially represent superior material for biofuel. However, diatoms require the nutrient silicate in addition to nitrogen and phosphorus found in wastewater, and silicate concentrations, fluxes, and cycling have never been studied under such conditions. A mathematical model (we previously developed for benthic lake environments) based on a system of ordinary differential equations to predict the proportional growth and decay of silicate pools within a closed system, was re-parameterized for wastewater conditions and solved (using MATLAB). The pilot treatment system (at the Jones Island Wastewater Treatment Plant Milwaukee, WI), consisted of troughs (4 troughs, each approximately 0.5 x 3.0 x 1.5 m) in which secondary-treated domestic wastewater flowed over naturally-growing alga. Weekly measurements were made of the pools of silicate (i.e. dissolved and particulate biogenic silicate) by measuring water flowing into and out of troughs, and the material in the troughs. Inflow of dissolved silicate ranged from 12-111 uM, outflow of dissolved silicate ranged from 12-98 uM, inflow of particulate biogenic silicate ranged from 0.11-7.4 uM, and outflow particulate biogenic silicate ranged from 0.1-28 uM. Biomass of silica in the Cladophora/diatom assemblage- averaged 229 uM Si/g dry mass. First attempts at parameterizing the model used the proportional relationship between inflow and outflow concentrations, but large fluctuations in biomass invalidated steady-state assumptions. Currently, we are re-structuring the models into an open system and re-tuning parameter values. Ultimately our goal is to make predictions about rates of silicate cycling under different flow rates and nutrient concentrations in order to determine the optimal conditions, or algal biomass and thus-lipid and cellulose production.