Which contaminants are targeted in biological treatment processes?

In biological treatment processes, the primary focus is on degrading organic matter and nitrogen compounds. This is because biological treatment relies on microorganisms, such as bacteria and protozoa, which thrive on organic materials as their source of energy. These microorganisms metabolize organic substances, breaking them down into simpler compounds. Additionally, nitrogen compounds, including ammonia and nitrates, are significant contributors to water pollution and can cause harmful environmental effects. Biological treatment processes often incorporate steps like nitrification and denitrification to effectively manage nitrogen levels in wastewater.

While the other options mention pollutants that may also require treatment, they are not the primary targets of biological treatment methods. Heavy metals and toxins often necessitate physical or chemical processes for removal due to their non-biodegradable nature. Pathogens may be dealt with in biological processes, but they do not represent the main goal; usually, additional measures are taken to ensure that pathogens are effectively removed. Chlorinated solvents and pesticides tend to require specialized technologies for degradation or removal, as many of these substances are resistant to biological processes. Therefore, the emphasis on organic matter and nitrogen compounds positions them as the correct focus of biological treatment in wastewater management.