gaseous emission

The correct answer is **d) Rainwater Harvesting Systems**. While rainwater harvesting systems can contribute to water pollution, they are not a primary source of gaseous emissions in the context of water treatment.

The correct answer is **b) Climate change**. Methane is a potent greenhouse gas that contributes significantly to global warming.

The correct answer is **a) Activated Carbon Adsorption**. Activated carbon can effectively capture and adsorb various VOCs from the air stream.

The correct answer is **d) All of the above**. Source reduction encompasses all these approaches to minimize the overall impact of gaseous emissions.

The correct answer is **c) Increased production costs**. While controlling emissions may require investments in technology and practices, the long-term benefits outweigh the costs in terms of environmental and public health protection.

Here's a sample solution for the exercise:

**1. Two technologies for methane reduction:**

• a) Biogas Upgrading: This technology involves removing carbon dioxide (CO2) and other impurities from biogas (which is primarily methane) to produce a higher quality methane gas. This upgraded methane can then be used as a fuel source or injected into the natural gas grid.
• b) Thermal Oxidation: This method involves burning the methane-rich biogas in a controlled combustion chamber at high temperatures. The heat generated can be recovered for use in the plant or as a source of energy.

**2. Explaining the technologies:**

• Biogas Upgrading: This process typically uses membrane separation technology, where a semi-permeable membrane selectively allows methane to pass through while retaining other gases.

  • Advantages: Produces high-quality methane for use as a renewable energy source.
  • Disadvantages: Can be costly to implement, especially for larger-scale installations.

• Thermal Oxidation: This method involves passing biogas through a combustion chamber where it reacts with oxygen at high temperatures, converting methane to carbon dioxide and water.

  • Advantages: Relatively simple technology, high efficiency in reducing methane emissions.
  • Disadvantages: Requires additional energy input for combustion, potential for air pollution if not properly managed.

**3. Technology Suggestion:**

• Considering Factors: The choice depends on the specific plant's size, available energy sources, and budget constraints. Biogas upgrading might be suitable for larger plants with the capacity to utilize high-quality methane, while thermal oxidation could be more cost-effective for smaller plants.
• Recommendation: Based on the specific scenario, a feasibility study should be conducted to evaluate both technologies in detail and determine the most appropriate solution for the wastewater treatment plant.