All questions of Environmental Engineering for Civil Engineering (CE) Exam

Respectively, what is the non-carbonate hardness of the water sample?

To determine the non-carbonate hardness, we need to subtract the carbonate hardness (alkalinity) from the total hardness.

Non-carbonate hardness = Total hardness - Carbonate hardness
Non-carbonate hardness = 200 - 260
Non-carbonate hardness = -60 mg/L as CaCO3

This result is not possible, as the non-carbonate hardness cannot be negative. It is likely that there is an error in one of the measurements or calculations.

Testing for Leakage in Pipeline Joints
Leakage testing in pipelines is crucial to ensure the integrity and safety of the infrastructure. The two primary methods used for this are water tests and air tests.
1. Water Test
- This method involves filling the pipeline with water and pressurizing it to a specified level.
- The water acts as a medium to identify any leaks, as escaping water will indicate a failure at the joints or along the pipeline.
- Water tests are particularly effective for large pipelines and are often used in potable water systems to ensure no contamination occurs.
2. Air Test
- In this method, the pipeline is filled with air and pressurized to a designated level.
- Air tests are quicker to execute and can be used for smaller pipelines or systems where water is not suitable.
- The presence of any escaping air signals a leak, allowing for targeted repairs.
3. Benefits of Using Both Methods
- Combining both tests enhances the reliability of leakage detection.
- Water tests provide a thorough examination under conditions that simulate normal operational stress.
- Air tests serve as a preliminary check, often performed before a water test to narrow down potential leak points.
Conclusion
- Leakage testing is essential for maintaining pipeline integrity and preventing failures.
- Using both the water and air tests allows for a more comprehensive assessment of the pipeline system, ensuring it is safe and operational before being put into service.
Thus, the correct answer is indeed option 'D', as both methods are effective in identifying leaks in pipe joints and pipeline systems.

Alkalinity in Water

Alkalinity is a measure of the water's ability to neutralize acids. It is an important parameter in water quality assessment as it helps in determining the water's buffering capacity and its resistance to pH changes. Alkalinity is expressed in terms of milligrams per litre (mg/L) and is typically reported as milligrams of equivalent calcium carbonate per litre (mg/L CaCO3).

Calcium Carbonate as Equivalent

The alkalinity in water is expressed as milligrams per litre in terms of equivalent calcium carbonate (CaCO3). This means that the alkalinity concentration is reported as the amount of calcium carbonate that would be required to neutralize the acid in the water sample.

Calcium Carbonate as a Common Standard

Calcium carbonate is chosen as the common standard for expressing alkalinity because it is a common and abundant compound found in nature. It is also the primary component of many minerals, such as limestone and chalk. Calcium carbonate is chemically stable and has a well-defined stoichiometry, making it suitable for use as an equivalent standard.

Calcium Carbonate Equivalent Calculation

To determine the alkalinity in water, a titration method is commonly used. In this method, a known volume of the water sample is titrated with a standardized acid solution until the pH reaches a certain endpoint. The amount of acid required to reach the endpoint is then used to calculate the alkalinity.

The alkalinity is calculated by multiplying the volume of acid used by its normality and dividing by the volume of the water sample. To express the alkalinity in terms of milligrams per litre of calcium carbonate, the result is multiplied by the equivalent weight of calcium carbonate (50.04 mg/mmol).

Advantages of Calcium Carbonate Equivalent

Using calcium carbonate equivalent as the standard for expressing alkalinity has several advantages:

1. Standardization: Calcium carbonate provides a standardized reference point for comparing alkalinity values across different water samples.

2. Abundance: Calcium carbonate is a naturally occurring compound that is widely available, making it easy to obtain and use as a standard.

3. Chemical Stability: Calcium carbonate is chemically stable and does not readily react with other substances in water, ensuring the accuracy and reliability of alkalinity measurements.

4. Stoichiometry: Calcium carbonate has a well-defined stoichiometry, simplifying the calculations involved in determining alkalinity.

In conclusion, alkalinity in water is expressed as milligrams per litre in terms of equivalent calcium carbonate (CaCO3) due to its abundance, chemical stability, well-defined stoichiometry, and suitability as a standard for comparing alkalinity values.

Gravity Filters:

Gravity filters are a type of water treatment filters that operate under the influence of gravity alone. These filters rely on the force of gravity to allow water to pass through the filter media and remove impurities. Among the given options, both slow sand filters and rapid sand filters are examples of gravity filters.

Slow Sand Filters:

Slow sand filters are a type of gravity filter used for water treatment. They consist of a bed of fine sand through which water is passed at a slow rate. The filter media in slow sand filters is typically 0.15 to 0.35 mm in size and is often layered with different sizes of sand to promote effective filtration. The process of filtration in slow sand filters involves physical straining, biological activity, and adsorption of impurities onto the filter media. Slow sand filters are known for their high efficiency in removing pathogens, turbidity, and organic matter from water.

Rapid Sand Filters:

Rapid sand filters are another type of gravity filter commonly used in water treatment plants. They are designed to remove suspended solids and turbidity from water at a higher flow rate compared to slow sand filters. Rapid sand filters typically consist of a layer of coarse sand, followed by a layer of fine sand, and sometimes an additional layer of anthracite coal or activated carbon. The filter is operated under gravity, allowing water to pass through the filter media and collect in the bottom of the filter bed. Rapid sand filters are efficient in removing particulate matter and improving water clarity.

Pressure Filters:

Unlike slow sand filters and rapid sand filters, pressure filters do not operate under the influence of gravity alone. Pressure filters use pressure to force water through the filter media, rather than relying on the force of gravity. The pressure can be created using a pump or by placing the filter media in a pressurized vessel. Pressure filters are commonly used in applications where a higher flow rate is required or where there is limited space for a gravity filter system.

Conclusion:

In conclusion, both slow sand filters and rapid sand filters are examples of gravity filters. These filters operate under the influence of gravity alone and rely on the force of gravity to allow water to pass through the filter media. Pressure filters, on the other hand, do not operate under gravity and use pressure to force water through the filter media.

The Oxygen Sag Curve of a River and its Significance

The Oxygen Sag Curve is a graphical representation of the variation of dissolved oxygen concentration in a river with respect to the distance downstream from a point source of pollution. It is an important tool in the study of water pollution and its effects on the aquatic ecosystem.

Significance of the Oxygen Sag Curve

The Oxygen Sag Curve helps in determining the extent of pollution in a river and its impact on the aquatic ecosystem. It provides information on the concentration of dissolved oxygen in the river at different points downstream from the source of pollution.

The Oxygen Sag Curve represents the relationship between the amount of biodegradable organic matter present in the river and the concentration of dissolved oxygen. As the organic matter is decomposed by microorganisms, the demand for oxygen increases and the concentration of dissolved oxygen decreases.

What does the Oxygen Sag Curve represent?

The Oxygen Sag Curve represents the Dissolved Oxygen Deficit in the river. It is the difference between the initial dissolved oxygen concentration and the minimum dissolved oxygen concentration observed downstream from the source of pollution.

The Dissolved Oxygen Deficit is an indication of the extent of pollution and its impact on the aquatic ecosystem. It affects the survival of aquatic organisms and their ability to carry out metabolic processes such as respiration.

Conclusion

The Oxygen Sag Curve is an important tool in the study of water pollution and its effects on the aquatic ecosystem. It provides information on the concentration of dissolved oxygen in the river at different points downstream from the source of pollution and represents the Dissolved Oxygen Deficit in the river.