Picos-Corrales et al. 2020 - Chitosan and bean straw bioflocculants

Picos-Corrales and colleagues compared chitosan and bean straw flour as bioflocculants for agricultural wastewater and river-water treatment in Sinaloa, Mexico. This is mitigation and water-remediation evidence: it reports removal of turbidity and metals from wastewater or river-water matrices, not occurrence concentrations in consumer products or ingredients.

Key numbers

In agricultural wastewater, the authors reported average starting conditions of about 160 NTU, pH 6.33, and 1175 mg/L total dissolved solids for the CCM mixed drainage sample; about 50 NTU, pH 7.48, and 292 mg/L TDS for La Escalera; and about 22 NTU, pH 7.63, and 1015 mg/L TDS for Elota-San Ignacio. Figure 4 reports that, in CCM water, 10 mg/L flocculant reduced turbidity substantially and that residual turbidity was about 10 NTU with 30 mg/L bean straw flour and about 6 NTU with 5 mg/L chitosan. For La Escalera and Elota-San Ignacio samples, chitosan lowered final turbidity near 5 NTU.

Table 1 reports water-quality parameters before and after flocculation. For Elota-San Ignacio wastewater, raw water had turbidity 22 NTU, TDS 1015 mg/L, pH 7.63, sulfate 90 mg/L, nitrate 6 mg/L, and Fe 0.185 mg/L. Chitosan at 15 mg/L reduced turbidity to 3 NTU and Fe to 0.080 mg/L; bean straw flour at 30 mg/L reduced turbidity to 16 NTU and left Fe at 0.182 mg/L. For CCM wastewater, raw water had turbidity 160 NTU, TDS 1175 mg/L, pH 6.33, phosphate 1.00 mg/L, sulfate 225 mg/L, nitrate 10 mg/L, and Fe 0.049 mg/L. Chitosan at 5 mg/L reduced turbidity to 6 NTU and Fe to <0.010 mg/L; bean straw flour at 30 mg/L reduced turbidity to 10 NTU and Fe to <0.010 mg/L; commercial poly(aluminum chloride) at 5 mg/L reduced turbidity to 4 NTU and Fe to 0.027 mg/L.

Table 2 reports urban river-water parameters. For Tamazula River water, raw water had turbidity 32 NTU, TDS 129 mg/L, pH 7.60, phosphate 0.45 mg/L, sulfate 30 mg/L, Fe 0.238 mg/L, and Mn 0.095 mg/L. Chitosan at 5 mg/L reduced turbidity to 3 NTU, Fe to 0.052 mg/L, and Mn to 0.010 mg/L; bean straw flour at 30 mg/L reduced turbidity to 18 NTU, Fe to 0.216 mg/L, and Mn to 0.079 mg/L. For Humaya River water, raw water had turbidity 29 NTU, TDS 80 mg/L, pH 8.39, phosphate 0.49 mg/L, sulfate 15 mg/L, Fe 0.190 mg/L, and Mn 0.080 mg/L. Chitosan at 1 mg/L reduced turbidity to 7 NTU, Fe to 0.049 mg/L, and Mn to 0.015 mg/L; bean straw flour at 30 mg/L reduced turbidity to 21 NTU, Fe to 0.200 mg/L, and Mn to 0.079 mg/L.

Figure 10 and the results text describe synthetic Mn-spiked river-water tests using Tamazula River matrix at 15 NTU with Mn concentrations of 0.120, 0.170, 0.280, 0.374, and 0.424 mg/L. The authors state that bean straw flour removed close to 40% Mn at 0.424 mg/L, while chitosan produced river water with Mn below the Mexican regulatory level of <0.15 mg/L across the tested range.

The text also reports synthetic Cu-spiked river-water tests at 1.35 and 2.75 mg/L Cu. Bean straw flour had low Cu entrapment, while chitosan removed about 50% Cu from both samples; for the 2.75 mg/L starting concentration, the authors state that chitosan could bring Cu within the Mexican limit of <2.0 mg/L.

Methods (brief)

Chitosan was a medium-molecular-weight shrimp-shell product from Sigma-Aldrich, 190-310 kDa with 75-85% deacetylation, used from a 5000 mg/L stock in 1% acetic acid. Bean straw flour came from Phaseolus vulgaris L. agricultural byproduct collected after harvest in Sinaloa, triturated, and sieved through 250 and 425 um sieves without hazardous chemical modification. The bean straw flour composition was reported as ash 9%, protein 3%, lipids 0.2%, carbohydrate 47%, crude fiber 36%, and moisture 4.8%.

Jar tests used 500 mL water samples at 25 C with 100 rpm rapid mixing for 5 min, then 60 rpm mixing for 30 min, followed by 25 min settling. The pH was not adjusted before flocculant addition. Turbidity was measured with a Hach 2100N turbidimeter; pH and TDS were measured with Thermo Scientific Orion Star meters. Heavy metals and anions were measured with a HANNA Instruments HI-83200 photometer following the instrument manual.

Implications

Certification: Do not use these values in product or ingredient occurrence pools. They are remediation performance values from wastewater and river-water treatment, with some Mn and Cu tests run on synthetic spiked river-water matrices.

Courses: Useful for supply-chain and co-packer training on bioflocculation as a pre-discharge or water-treatment lever, especially where agricultural drainage or river intake water carries turbidity plus Fe/Mn/Cu burdens.

App: Context only. The paper does not support consumer-facing product contamination estimates.

Wiki pages this source may touch

• remediation-evidence
• supply-chain-screening
• iron
• manganese
• copper
• index

Verification notes

The DOI, author list, journal, and year were taken from the ACS Omega PDF. The paper is not occurrence evidence: products and ingredients are intentionally empty, and the matrices are wastewater, river-water, and bioflocculation contexts. Table 1 has a formatting gap in the extracted text for the first ES phosphate value, so the source page preserves only clearly aligned values and avoids inferring the missing cell.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.