Heavy metals occurrence in the pig farm environment and the effects on an anaerobic digestion process of pig manure

The objective of this study was to assess the levels of heavy metals in animal feed, manure, and sediment in the farm environment's field water supply and drainage system. Samples of animal feed were collected from pigs at various growth stages, as well as feces and sediment samples from the discharge system leading to the Day River. An analysis of the samples found concentrations of Cu and Zn that ranged from 61 to 2,731 and 151-4,269 mg/kg center dot TS, respectively, which was significantly higher than the acceptable Vietnamese standards for agricultural land. The ecological risk coefficient in the estuary to the open channel potential ecological index (RI) exceeded 600, indicating a high level of ecological risk in the contaminated pig farm area. Furthermore, the study assessed the impacts of Cu, Fe, Pb, and Zn on anaerobic biodegradation of pig manure, revealing that levels of these metals from 0-40 mg/L, negatively affected biogas yield, with a decrease from 4.38% to 15.30%. Moreover, the treatment efficiency of chemical oxygen demand (COD) and total solids (TS) was affected adversely with a decline from 35.57% to 43.86%. The study found that the most impactful metals on the biogas yield were Pb, Zn, and Cu in that order, respectively. Conversely, the concentration of Fe level of 12 mg center dot Fe/L demonstrated a significant increase in the biogas yield and higher efficiency of TS and COD treatment compared to non-metallic samples. However, an increase in concentration from 20 to 40 mg center dot Fe/L resulted in an adverse effect, reducing the biogas yield. Essentially, this research was conducted to aid in management control measures to regulate the input of raw materials and feed, drinking water, and sanitation procedures implemented in the pig site. This would assist in limiting the propagation of heavy metals into the immediate environment.