Valorization of treated wastewater from the soaking of baby alpaca skin fur.

Baby alpaca fur industry generates considerable wastewater during the soaking process, which contains high levels of total suspended solids (TSSs), proteins, and salts, among other components. The valorization of wastewater after precipitation, coagulation-flocculation, and aeration treatments was evaluated for use in irrigation water, fertigation, groundwater recharge, concrete construction, and disposal. The precipitation treatment sludge and the coagulation-flocculation treatment were evaluated as a protein source, soil quality improvement, and disposal. The treatment system included evaluations of nine pH levels, seven coagulant doses, and seven aeration times. The contents of TSSs, chemical oxygen demand (COD), total Kjeldalh nitrogen (TKN), ammonia nitrogen (N-NH3), and oils and fats (O&G), among other parameters, were determined in the treated and untreated wastewater. Before entering the treatment system, the physicochemical characterization of the wastewater showed a high concentration of parameters related to organic matter and dust, such as O&G, five-day biological oxygen demand (BOD5), COD, TSSs, TKN, and N-NH3. The optimal removal parameters were pH 12 for the chemical precipitation of proteins, a dose of 480 mg/L FeCl3 as a coagulant for TSSs removal, and 150 min of aeration; removal efficiencies of 99.02 %, 77.49 %, 79.93 %, and 64.62 % for TSSs, Cod, TKN, and N-NH3, respectively, were obtained. The wastewater after treatment can be used for groundwater recharge and concrete construction, and the wastewater with 2 % dilution can be used for irrigation water and fertigation. The sludge after precipitation is rich in protein and can be used as a protein source or soil quality improver.

Stabilization of residual mercury from gold mining as metacinnabar and cinnabar in ball mills on a pilot scale.

Waste liquid mercury generated as a by-product of the Merrill-Crowe process in gold mining and recovered from mercury-containing waste must be stabilized for secure storage or disposal. This study developed a procedure for mercury stabilization. A ball mill with a 0.5 m3 capacity and a rotational speed of 43 rpm was used to stabilize the residual mercury with sulfur. The treatments were conducted for 30, 60, and 90 min at mercury: sulfur molar ratios of 1.0, 0.8, and 0.67. The ball loading ratio was 7.0 with residual mercury, and the temperature was below 40 °C. The treatment efficiency was evaluated by measuring the concentrations of mercury and other metals using the Toxicity Characteristic Leaching Procedure (TCLP), examining the stabilized residual mercury by X-ray diffraction, and conducting bioassays on Daphnia magna and Lactuca sativa. Principal component analysis (PCA) was performed on the aforementioned variables. The 90-min treatment, with a mercury-to-sulfur molar ratio of 0.67, stabilized mercury mainly as cinnabar compared with the other treatments and presented leachate mercury values below the detection limit <0.003. The leachate from the treatments also showed values of 21.28-38.44 toxic units, classified as very toxic, and generated toxicity, particularly for D. magna, because of the presence of other metals such as Al, Ba, B, Ca, Cu, Cr, Fe, Mn, Ni, and Zn. The variability of the residues in the PCA analysis was explained by the treatment effect and the presence of other metals in the residual mercury. The stabilized residual mercury obtained was classified as non-hazardous and could be stored or disposed of as ordinary waste in a security landfill.

The predictive model of hydrobiological diversity in the Asana-Tumilaca basin, Peru based on water physicochemical parameters and sediment metal content.

The hydrobiological diversity in the basin depends on biotic and abiotic factors. A predictive model of hydrobiological diversity for periphyton and macrobenthos was developed through multiple linear regression analysis (MLRA) based on the physicochemical parameters of water (PPW) and metal content in sediments (MCS) from eight monitoring stations in the Asana-Tumilaca Basin during the dry and wet seasons. The electrical conductivity presented values between 47.9 and 3617 µS/cm, showing the highest value in the Capillune River due to the influence of geothermal waters. According to Piper's diagram, the water in the basin had a composition of calcium sulfate and calcium bicarbonate-sulfate. According to the Wilcox diagram, the water was found to be between good and very good quality, except for in the Capillune River. The Shannon-Wiener diversity indices (H') were 2.62 and 2.88 for periphyton, and 2.10 and 2.44 for macrobenthos, indicating moderate diversity; for the Pielou's evenness index (J'), they were 0.68 and 0.70 for periphyton, and 0.68 and 0.59 for macrobenthos, indicating similar equity, in the dry and wet seasons, respectively, for both indices. In the model there were three cases, where the first two cases only worked with PPW or MCS, and case 3 worked with PPW and MCS. For case 3, the predicted values for H' and J' of periphyton and macrobenthos concerning those observed presented correlation coefficients of 0.7437 and 0.6523 for periphyton and 0.9321 and 0.8570 for macrobenthos, respectively, which were better than those of cases 1 and 2. In addition, principal component analysis revealed that the As, Pb, and Zn contents in the sediments negatively influenced the diversity, uniformity, and richness of the macrobenthos. In contrast, Cu and Cr had positive impacts because of the adaptation processes.