Which of the following compounds can negatively affect anaerobic digestion processes?

Heavy metals and sulfides can severely impact anaerobic digestion processes. In anaerobic digestion, a microbial community breaks down organic matter in the absence of oxygen to produce biogas and digestate. Heavy metals such as lead, mercury, and cadmium are toxic to many microorganisms, disrupting their metabolic processes and potentially leading to decreased biogas production. These metals can accumulate in the microbial cells, inhibiting their growth and activity.

Sulfides, particularly hydrogen sulfide (H2S), can also be detrimental. Although some level of sulfide is naturally produced during anaerobic digestion, excessively high concentrations can be toxic to the bacteria responsible for the digestion process. Hydrogen sulfide can lead to corrosion of equipment and can inhibit the growth of methanogenic organisms, which are essential for converting organic substrates into methane.

The other options include compounds that are generally beneficial or neutral in relation to the anaerobic digestion process. Organic nutrients and trace elements can support microbial activity, while nitrogen gases and carbon dioxide are often byproducts of digestion. Similarly, phosphates and chlorides do not typically hinder anaerobic digestion processes to the extent that heavy metals and sulfides do.