Question 1 Metals present in municipal wastewater may still be present in treated sewage sludge; __________. cause damage to the municipal works interfere with coagulation and flocculation kill bacteria used in wastewater treatment a and c but not b all of the above Question 2 Historically, the use of chlorine bleach has made the pulp and paper industry an important source of __________ contamination. dioxin chromium polychlorinated biphenyls (PCBs) Question 3 Chlorination of drinking water is highly effective at killing __________. bacteria protozoa viruses

Question 1 Metals present in municipal wastewater may still be present in treated sewage sludge; they can cause damage to the municipal works, interfere with coagulation and flocculation, and even kill bacteria used in wastewater treatment. Therefore, the correct answer is “all of the above.”

Metals are one of the major pollutants present in municipal wastewater due to various industrial, domestic, and commercial sources. While wastewater treatment processes aim to remove these contaminants, metals can still persist in treated sewage sludge. This is a significant concern as sewage sludge is often used as a fertilizer or disposed of in landfills, which can lead to the release of metals into the environment.

Metals can cause damage to municipal works such as pipes, pumps, and other infrastructure. They can corrode the metal surfaces, leading to structural damage and degradation of the wastewater treatment plants. Additionally, metals can interfere with coagulation and flocculation processes, which are crucial for removing suspended solids and contaminants from wastewater. Interference in these processes can reduce the efficiency of wastewater treatment and result in poor quality effluent.

Furthermore, metals can also have detrimental effects on the biological processes involved in wastewater treatment. Bacteria play a vital role in the degradation of organic matter and the removal of nutrients from wastewater. Unfortunately, metals like copper, zinc, and silver can have toxic effects on these bacteria, ultimately killing them or reducing their activity. This can disrupt the overall microbial balance in wastewater treatment systems and impact treatment efficiency.

Given these facts, it is evident that metals in treated sewage sludge can cause damage to municipal works, interfere with coagulation and flocculation, and harm bacteria used in wastewater treatment. Therefore, the correct answer to question 1 is “a and c but not b.”

Question 2: Historically, the use of chlorine bleach has made the pulp and paper industry an important source of dioxin contamination.

Dioxins are a group of highly toxic and persistent organic pollutants. They can be formed as byproducts during various industrial processes, including the production of chlorine-based bleaching agents. The pulp and paper industry has historically used chlorine bleach extensively as a bleaching agent to whiten pulp and paper products.

Unfortunately, the use of chlorine bleach in the pulp and paper industry has contributed significantly to dioxin contamination. During the bleaching process, organic compounds present in the pulp react with chlorine, leading to the formation of dioxins. These dioxins can then enter the environment through the discharge of wastewater from pulp and paper mills.

Dioxins are known for their adverse effects on human health and the environment. They are classified as persistent organic pollutants (POPs) due to their long-term persistence in the environment and bioaccumulative nature. Dioxins can bioaccumulate in the food chain and pose a risk to human health when consumed through contaminated food or water.

Therefore, the correct answer to question 2 is “dioxin.”

Question 3: Chlorination of drinking water is highly effective at killing bacteria, protozoa, and viruses.

Chlorination is a widely used disinfection method for treating drinking water. It involves the addition of chlorine or chlorine-based compounds to water to destroy or inactivate pathogenic microorganisms.

Bacteria, protozoa, and viruses are the primary microorganisms of concern in drinking water as they can cause various waterborne diseases. Chlorine, when added to water, reacts with these microorganisms, leading to the destruction of their cell structure or inhibition of their metabolic processes.

Bacteria are single-celled microorganisms that can cause illnesses such as diarrhea, dysentery, and cholera. Protozoa are larger microorganisms that include parasites like Giardia and Cryptosporidium, which can cause gastrointestinal diseases. Viruses are even smaller than bacteria and can cause diseases like hepatitis, norovirus infection, and rotavirus infection.

Chlorination is highly effective at killing or inactivating these harmful microorganisms, making it an essential step in ensuring the safety of drinking water. However, it is important to note that chlorination may not be effective against all microorganisms, such as certain protozoan cysts and some viruses. In such cases, additional treatment steps may be required to ensure the complete removal or inactivation of these pathogens.

Therefore, the correct answer to question 3 is “all of the above.”