Introduction:
The pH value is a measure of the acidity or alkalinity of a solution. It is determined by the concentration of hydrogen ions (H+) in the solution. pH values range from 0 to 14, with pH 7 considered neutral, pH less than 7 considered acidic, and pH greater than 7 considered alkaline or basic.

Explanation:
Fresh sewage is a mixture of waste materials, including organic and inorganic compounds, as well as water. It is generated from households, industries, and other sources and contains a variety of substances that can affect its pH value.

Acidity of fresh sewage:
Fresh sewage typically contains a high concentration of organic acids, such as acetic acid and lactic acid, which are produced by the decomposition of organic matter. These organic acids contribute to the acidity of sewage and lower its pH value. Additionally, the presence of other acidic substances, such as sulfuric acid from industrial sources or carbonic acid from the dissolution of carbon dioxide, can further decrease the pH of sewage.

Alkalinity of fresh sewage:
On the other hand, fresh sewage can also contain alkaline substances, such as ammonia (NH3) and bicarbonate ions (HCO3-). Ammonia is produced by the breakdown of nitrogen-containing compounds in sewage, while bicarbonate ions can be present in wastewater due to the dissolution of carbon dioxide. These alkaline substances can increase the pH value of sewage.

Factors affecting pH value:
The pH value of fresh sewage can vary depending on several factors, including the characteristics of the waste materials, the presence of certain chemicals or pollutants, and the activities of microorganisms involved in the decomposition process. Changes in pH can also occur as sewage undergoes biological treatment processes, such as anaerobic digestion or aerobic treatment.

pH value of fresh sewage:
Considering the acidic nature of organic acids and the alkaline nature of substances like ammonia and bicarbonate ions, the overall pH value of fresh sewage is usually more than 7, making option 'B' the correct answer.

Conclusion:
The pH value of fresh sewage is typically more than 7 due to the presence of both acidic and alkaline substances. However, it is important to note that the pH of sewage can vary depending on various factors and may require adjustments during the wastewater treatment process to ensure proper treatment and disposal.