Utilization of semi-continuous algae culture for the treatment of recycled dairy lagoon wash water

Authors: SCHWARTZ, GREGORY - California Polytechnic State University; Ibekwe, Abasiofiok - Mark; LUNDQUIST, TRYGVE - California Polytechnic State University; MURINDA, SHELTON - California Polytechnic State University; MURRY, MARCIA - California Polytechnic State University

Submitted to: Current Biochemical Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2020
Publication Date: 6/22/2021
Citation: Schwartz, G., Ibekwe, A.M., Lundquist, T., Murinda, S., Murry, M.A. 2021. Utilization of semi-continuous algae culture for the treatment of recycled dairy lagoon wash water. Current Biochemical Engineering. 7(1):72-82. https://doi.org/10.2174/2212711907666210622153521.
DOI: https://doi.org/10.2174/2212711907666210622153521

Interpretive Summary: There is a critical and urgent need to control manure-derived greenhouse gases and nutrient pollution from concentrated animal feeding operations (CAFOs) while reclaiming water and nutrients, and at the same time allow competitive animal production in a global market. However, technologies and methods to reclaim nutrients from wastewater, with minimal environmental impact, have not kept pace with CAFO development. In this study, we used a leading candidate technology for accelerated manure nutrient recycling — algae-based animal feeds bioconversion ponds that may play a significant role in the conversion of manure nu¬trients to animal feed where land area for traditional crops or for manure disposal is limited. The algae ponds were paddle-wheeled, mixed raceways that simulate standard 30-cm deep algae production ponds. The main objectives of this study were to quantify dilution rate requirements for successful algae production in ponds fed dairy lagoon wash water effluent (DLE), and to evaluate seasonal nutrient removal rates, of N and P, for algal ponds fed DLE as the primary nutrient source. This study demonstrates that algal/bacterial nutrient reduction of diluted dairy wash water can be achieved even when used as a sole nutrient source. During this long term, outdoor, semi-continuous culture study, it was found that HRAPs can remove a significant fraction of the N (20-74%) and P present in dairy wash water. The best results were obtained with the wastewater making up less than 8% of the daily liquid input, about a 12:1 or higher dilution. Nutrient uptake rates were greatly impacted by season, with colder seasons limiting the nutrient removal. Seasonal shifts of microalgal species were observed. This information will be of interest to water utility agencies, US-Department of Agriculture (USDA), US-Environmental Protection Agency (USEPA), US-Department of Energy (DOE), the World Health Organization(WHO), and the dairy industry.

Technical Abstract: Utilization of animal wastes in algal culture has proven to be challenging. The utilization of “free” nutrients has drawn many researchers and industry to developing business models that call for the use of these free nutrients which comes at a cost. Some of these costs include reduced productivity, increased contamination, lower value target markets, and lower treatment capabilities (for wastewater treatment applications). This paper evaluates the impact of dairy lagoon effluent on productivity and wastewater treatment ability. Screened dairy lagoon wash water was fed to four three square meter outdoor open paddlewheel algal cultivation reactors. The units were operated semi-continuously for one and a half years. Seasonal productivity and nutrient uptake rates, for nitrogen (N) and phosphorous (N), were measured against wastewater dilution requirements. Seasonal algal species dominance was also recorded. Wastewater was added at two levels, and the lower level was supplemented with synthetic fertilizer. Seasonal N uptake rates ranged from 0.5 to 1.2 grams of N uptake per square meter per day while P uptake ranged from 0.17 to 0.3 grams of P per square meter per day depending on season and hydraulic residence time (HRT). N removal efficiency ranged at 40 to 70% for semicontinuous operation, depending on HRT, season, and dilution of influent wastewater which was made up from 1.5% to 13% of the daily water exchange. Algal reactors tended to be N limited due to the inability to add enough dairy wastewater to mitigate the high turbidity and dark color. Treatments with lower levels of added dairy wastewater tended to show higher nutrient removal. Algal culture from dairy wash water could benefit from a pretreatment step to reduce turbidity and color, thereby promoting algal growth and productivity.