JNTU B.Tech III ENVIRONMENTAL ENGINEERING Previous Question Paper (August/September - 2021 - R18)

Surface water and groundwater quality differ significantly due to their exposure to environmental factors and geological interactions. Surface water, such as rivers and lakes, is highly susceptible to contamination from atmospheric deposition, surface runoff, and human activities, leading to higher levels of suspended solids, turbidity, and microbial pathogens. It typically has lower mineral content but fluctuates rapidly in quality based on seasonal changes and pollution events.

In contrast, groundwater is generally clearer and more consistent in quality because it undergoes natural filtration through soil and rock layers, which removes suspended particles and many pathogens. However, groundwater often contains higher concentrations of dissolved minerals, such as calcium, magnesium, iron, and manganese, acquired through prolonged contact with aquifer materials. While groundwater is less prone to immediate surface pollution, it is vulnerable to long-term contamination from leaching of chemicals, pesticides, and industrial wastes, which are often difficult to remediate once introduced into the aquifer.

Drinking water standards for Fluorides and Nitrates are defined to protect public health from specific toxicological risks associated with their consumption.

Fluoride: The acceptable limit is 1.0 mg/L, with a permissible limit of 1.5 mg/L in the absence of an alternate source. Fluoride is significant because low concentrations (around 0.5–1.0 mg/L) help prevent dental caries by strengthening tooth enamel. However, excessive intake exceeding 1.5 mg/L leads to dental fluorosis (mottling of teeth) and, at higher levels, skeletal fluorosis, which causes severe bone deformities and joint pain.

Nitrates: The acceptable limit is 45 mg/L (as NO3). Nitrates are significant primarily due to their role in causing methemoglobinemia, or 'blue baby syndrome,' in infants. In the digestive system, nitrates are reduced to nitrites, which bind to hemoglobin in the blood to form methemoglobin, reducing the blood's oxygen-carrying capacity. High nitrate levels in water are typically indicative of contamination from sewage, agricultural fertilizers, or animal waste.