Skip to main content
ARS Home » Plains Area » Las Cruces, New Mexico » Cotton Ginning Research » Research » Publications at this Location » Publication #417532
Research Project: Improving the Production and Processing of Western and Long-Staple Cotton and Companion Crops to Enhance Quality, Value, and Sustainability

Location: Cotton Ginning Research

Title: Development and application of a polycationic soybean protein-based flocculant for enhanced flocculation and dewatering of dairy manure

Author
item AMALY, NOHA - University Of California, Davis
item HARRISON, SCOTT - Figure 8 Environmental
item Tumuluru, Jaya Shankar
item SUN, GANG - University Of California, Davis
item PANDEY, PRAMOD - University Of California, Davis

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2024
Publication Date: 1/6/2025
Citation: Amaly, N., Harrison, S., Tumuluru, J., Sun, G., Pandey, P.K. 2025. Development and application of a polycationic soybean protein-based flocculant for enhanced flocculation and dewatering of dairy manure. Water Research. 371. Article 144050. https://doi.org/10.1016/j.chemosphere.2024.144050.
DOI: https://doi.org/10.1016/j.chemosphere.2024.144050

Interpretive Summary: Water recycling is gaining significance as water scarcity increases worldwide due to finite water resources. In the present study two waste water resources one from dairy manure and other from walnut hulling plants were studied for recycling application. The major challenge of recycling is the suspended solid and dewatering the sludge. A soya protein-based flocculant has been developed and tested for flocculation and dewatering of activated sludge. The soya protein-based flocculant displayed strong flocculation capabilities (96%), effectively reducing the filtration resistance of sludge by 55% and decreasing filter cake moisture content by 10%. The charge neutralization, bridging performance, and strong affinity to extracellular polymeric substances in protein contents in the sludge strongly facilitated both aggregation and dewaterability performance of soy protein-based flocculant.

Technical Abstract: In agricultural and waste management systems, dairy manure wastewater is often recycled for irrigation. However, a key challenge lies in handling suspended solids (SS) and effectively dewatering sludge. To address this, an innovative polycationic soybean protein-based flocculant (SPI+) was developed and applied to enhance flocculation and sludge dewatering efficiency. The polycationic protein chains of SPI+ were synthesized by grafting 2-(methacryloyloxy)ethyl trimethylammonium chloride (META) monomers onto soybean protein isolate (SPI) chains using an energy-efficient thiol-ene photografting method. This approach achieved a grafting ratio of 85%, endowing the SPI+ with a stable and strong positive zeta-potential (+30 mV) across a range of pH conditions. The SPI + exhibited exceptional flocculation performance, achieving a 96% flocculation efficiency, reducing sludge filtration resistance by 55%, and lowering filter cake moisture content by 10%. The SPI + flocculation and dewatering performance is comparable with synthetic-based commercial flocculant. This remarkable performance of SPI+ is attributed to its ability to effectively neutralize charges, form robust inter-particle bridges, and interact strongly with extracellular polymeric substances (EPS), particularly their protein components, within the sludge matrix. These properties significantly enhance both sludge aggregation and dewaterability. The underlying mechanisms of flocculation and dewatering were further elucidated using confocal imaging, surface morphology analysis of flocs, and quantification of EPS protein and polysaccharide content, providing valuable insights into its functional efficacy.