The aim of this work was to evaluate the role of three biopolymers used as coagulant–flocculant aids in the treatment of a high-load cosmetic industry wastewater (WW) located in Mexico. Discussion is based on a surface response methodology. When using guar, locust bean gum, and Opuntia mucilage, conductivity and turbidity removals as high as 20.1 and 67.8 % were found, respectively. Chemical oxygen demand (COD) removals as high as 38.6 % were observed. The maximum removal efficiency was found for mucilage, with 21.1 mg COD/mg polymer. At the end of the process, pH was in the range of 5.8–7.3 for an initial wastewater pH value of 5.6. The production of sludge was very dependent on the WW organic load. An analysis of some metal content in the sludges is presented. From the response surface analysis, it was observed that the parameter which strongly affected the removal of COD, turbidity, oil and greases (O&G), and the amount of sludge including their metal contents was the polymer dose. Only in the case of O&G removal was a combination of dose–wastewater organic load responsible for the removals. The values of R ² for the correlation process were between 0.5451 (O&G) and 0.7989 (COD). The p values for the different expressions were between 0.1985 (COD) and 0.7195 (O&G). The values of adequate precisior (AP) indicate how feasible it is to use the surface response analysis (AP > 4). Most of the analysis indicated that AP > 4, except in the case of the O&G removal analysis where AP = 2.9.

Thirty-nine plants naturally found in Brazilian Caatinga semiarid biome were screened using an in vitro fermentability testing focused in apparent organic matter digestibility (aOMD), gas, methane (CH₄), and short-chain fatty acid (SCFA) production. Three independent in vitro runs were carried out and plants were classified by CH₄ concentration as proportion of gas and per unit of apparent digested organic matter (aDOM). According to its CH₄ concentration on produced gas (mL/L), the plants were classified as low (> 110), medium (from 60 to 110), and high (< 60) anti-methanogenic potential. From evaluated plants, 3, 24, and 12 were classified as high, medium, and low anti-methanogenic potential. High anti-methanogenic potential plants Cnidoscolus phillacanthus (CnPh), Chloroleucon foliolosum (ChFo), and Anadenanthera macrocarpa (AnMa) produced 21.3, 34.3, and 35.9 mL CH₄/L of gas. Methane concentration for Myracrodruon urundeuva (MyUr) was 61.1 mL/L and classified as medium potential. However, CH₄ production per unit of aDOM was similar between MyUr and AnMa (3.35 and 2.68 mL/g, respectively). Molar proportions of acetate and propionate in SCFA produced by ChFo fermentation were 0.02 and 0.78 mmol/mol. Acetate to propionate ratios were 0.79, 0.03, 1.39, and 1.36 for CnPh, ChFo, AnMa, and MyUr, respectively. Greater aOMD were observed for Opuntia sp. and Calotropis procera (632 and 601 g/kg, respectively), which were classified as medium mitigating potential plants. AnMa, ChFo, CnPh, and MyUr are promising anti-methanogenic plants for ruminants. Selecting forages to feed ruminants in Caatinga is a potential strategy for enteric CH₄ emission reduction, and our in vitro results can support future research by indicating species to be evaluated in in vivo studies integrating mixed diets with performance, digestibility, and CH₄ production, yield, and intensity. Graphical abstract ᅟ