Multipurpose Dams & Water

Multipurpose Dam Projects

Introduction

Multipurpose dam projects are ambitious engineering endeavours that serve multiple purposes, combining water storage, hydropower generation, flood control and irrigation capabilities. By harnessing the power of rivers and creating reservoirs, these projects play a vital role in water resource management, sustainable energy production, and supporting agricultural and industrial development.

1. Multipurpose Dam Projects

Although building a dam over a river can be a costly and controversial project, the advantages are typically significant. Dams are frequently built with a variety of goals in mind. A dam could be useful for: the generation of electricity in hydroelectric power plants flood control irrigation tourism and leisure the provision of water creation of a habitat for wetland species access by boat to otherwise inaccessible areas. The disadvantages of dam projects can include: relocating people disrupting the life cycles of fish and other aquatic organisms changing the water supply for people who are downstream of the dam reducing the soil enrichment downstream of the dam the dam may become redundant as sediment in the river sinks to the bottom of the reservoir: this is called siltation they can be very expensive to build. 2. Where to Build a Dam

Choosing the location for a dam involves careful examination of various factors. Firstly, it should be situated in a narrow river valley to keep construction costs low. Additionally, for efficient hydroelectric power generation, the dam needs to be positioned higher up in the valley to maximise water pressure and potential energy. Whenever feasible, dams should be placed away from populated regions to minimise the risk of reservoir pollution.

3. Are Dams Sustainable?

Dams are often seen as a long-term solution for generating electricity, but they can face issues over time. Sediment carried by rivers can fill up the reservoir, the dam structure can deteriorate under pressure and eventually fail, and dams can harm the environment – particularly fish populations. These challenges indicate that dams may not always be sustainable solutions. On the other hand, some argue that dams are a better alternative to fossil fuel burning since they produce electricity without greenhouse gases and pollutants, placing them on one end of the sustainability spectrum, while fossil fuels sit at the other.

Sources, Impact and Management of Water Pollution

Introduction

Frequent utilisation of water often leads to its contamination, rendering it unsuitable for further use. Consequently, it is unsurprising that the three primary purposes of water align with the three primary sources of pollution.

1. Domestic Waste

Sewage refers to the waste material that is transported away from residential and commercial structures in urban areas as well as smaller rural communities. It is carried through a network of underground pipes known as sewers and is subsequently disposed of or treated to reduce its harmful effects.

1.1 Sewage treatment

Due to its high concentration of organic matter, sewage provides a favourable environment for the growth of microbial organisms. As a result, proper disposal of sewage is necessary, typically involving its release into water bodies. However, before disposal, sewage must undergo treatment processes to mitigate its potential adverse effects.

The primary objective of sewage treatment is to decrease the biological oxygen demand (BOD) of the sewage. BOD refers to the quantity of oxygen that would be consumed if the sewage were directly discharged into a river or lake. If this oxygen is depleted from the water body, it can lead to complications for the organisms residing in it, such as fish and insect larvae. More information about these issues can be found in the subsequent section on eutrophication.

The stages in a sewage treatment plant

1 Sewage outfall: Wastewater originating from residences, and occasionally from industries, is transported to a sewage treatment facility through a network of pipes known as sewers.

2 Screening tank: The wastewater undergoes a process of extracting large objects by passing them through a coarse grid, effectively removing them from the water.

3 Primary treatment, first settling tank: The solid organic matter, predominantly human waste, is allowed to settle at the bottom of the tank. This accumulated material is referred to as sludge and undergoes treatment in the sludge digester as outlined in step 7. The clarified water rises above the tank's edges and is then transferred to the subsequent phase of the treatment process.

4 Secondary treatment, oxidation: Subsequently, the water is pumped into a tank where oxygen is introduced through bubbling. This aeration process stimulates the proliferation of bacteria and other microorganisms that facilitate the decomposition of dissolved organic matter, consequently reducing the biological oxygen demand (BOD).

5 Secondary treatment, second settling tank: After the aeration process, the water proceeds to enter the second settling tank. In this tank, the bacteria settle at the bottom, contributing to the formation of additional sludge. Meanwhile, the clarified water surpasses the tank's boundaries and is released as effluent, indicating that it has been cleaned to a significant extent.

6 The effluent is discharged into the environment, usually a river.

7 Sludge digester: Within the sludge digester, an oxygen-free environment is established to promote the growth of bacteria capable of decomposing the sludge. As a result of this breakdown process, methane gas is released, which can be utilised as a fuel source through combustion.

8 The treated sludge can be dried in sludge lagoons and used as organic fertiliser on farmland.

In certain sewage treatment plants, tertiary treatment is conducted, which can include additional filtration of the effluent or the application of chlorine. These measures result in further purification of the effluent, ensuring a higher level of cleanliness, which is essential for safeguarding the ecosystem of the receiving habitat.

1.2 Improved sanitation

An enhanced sanitation facility is characterised as a system that effectively prevents direct contact between human excreta and individuals. This can be accomplished through the implementation of various types of toilets and latrines.

• Both flush toilets and pour-flush toilets incorporate a water seal to prevent odours. In the case of a flush toilet, a holding tank supplies the flushing water, while a pour flush toilet relies on manually poured water for flushing. Regardless of the type of toilet, the waste needs to be removed by:

either connecting to a sewerage system consisting of a network of pipes that collects human faeces, urine and wastewater, which is subsequently transported away from the premises, or connection to a septic system, which consists of an underground, sealed settling tank or similar onsite treatment systems. • A pit latrine with a platform is a type of sanitation facility that consists of a covered and enclosed pit. The platform is equipped with a seat positioned over a hole, or the platform itself has a hole. The purpose of the platform is to cover the pit and prevent direct exposure to its contents, with the exception of the hole. In some cases, these latrines may have ventilation systems in place to help mitigate odours and improve air circulation.

• A composting toilet is a type of dry toilet that utilises a composting process to treat human waste. In addition to human waste, materials such as vegetable scraps, straw, grass, sawdust and ash are added to the toilet. These additional materials help in the decomposition process and aid in the conversion of the waste into compost. Over time, through microbial action and decomposition, the mixture of waste and organic materials transforms into nutrient-rich compost that can be safely used as a soil amendment or fertiliser.

1.3 Water treatment

Water that is safe and suitable for domestic use, including drinking, washing and cooking, is referred to as potable water. To ensure its potability, water undergoes a series of treatment processes. These typically include coagulation, where chemicals are added to clump together impurities, followed by filtration to remove larger particles. Finally, disinfection methods, such as chlorination or ultraviolet (UV) treatment, are employed to kill or deactivate harmful microorganisms, making the water safe to consume.

Coagulants are substances that promote the aggregation of particles present in water, causing them to clump together and settle at the bottom of the container. After coagulation, the water goes through a filtration stage, typically using sand or other porous materials, to remove finer impurities.

To eliminate any remaining disease-causing organisms or pathogens, the filtered water is treated with chlorine, which acts as a disinfectant. This process, known as chlorination, ensures that any potentially harmful microorganisms are killed or inactivated, making the water safe for consumption. Managing Water-Related Diseases

Introduction

Frequent utilisation of water often leads to its contamination, rendering it unsuitable for further use. Consequently, it is unsurprising that the three primary purposes of water align with the three primary sources of pollution.

1. Cholera and Typhoid

Water serves as an excellent habitat for numerous organisms, thanks to its ability to support plant life and facilitate photosynthesis, resulting in abundant food availability. Moreover, water offers a nourishing environment for bacteria due to its nutrient content. Inadequate sanitation can lead to the introduction of pathogenic bacteria into drinking water through sewage, and consuming untreated water containing these pathogens can result in the transmission of diseases.

The key factor in preventing the transmission of these diseases among a population is to ensure the separation of sewage and drinking water. This highlights the importance of proper sanitation practices, where sewage is efficiently transported to treatment facilities, and water is treated before being provided for drinking purposes. By implementing these measures, the risk of diseases can be significantly reduced, safeguarding the health of the population.

Paying careful attention to maintaining good hygiene practices is extremely important, along with ensuring thorough cooking of food. It is crucial to avoid using contaminated water for washing food and to wash hands after coming into contact with any faecal matter. The use of effective latrines is vital for proper sanitation. By following these guidelines, the risk of disease transmission can be minimised.

If there are any concerns regarding the safety of drinking water, one simple method to eliminate the majority of harmful organisms is by boiling it. Boiling water can effectively remove potential pathogens, providing an added layer of protection.

2. Malaria

While cholera and typhoid are considered water-borne diseases, malaria, despite being associated with water, differs significantly in nature. Cholera and typhoid are bacterial diseases that can be transmitted through contaminated water. In contrast, malaria is caused by a parasite and is primarily transmitted through the bite of infected mosquitoes, with water serving as a potential breeding ground for these mosquitoes rather than directly transmitting the disease.

Malaria is caused by a microscopic organism called Plasmodium. The connection between malaria and water arises from the fact that the mosquito, which acts as a vector for transmitting the disease to humans, requires water for breeding. Mosquitoes lay their eggs in stagnant water, where the larvae develop. By biting infected humans, mosquitoes acquire the Plasmodium parasite, and they can subsequently transmit the parasite to other humans through their bites. To understand the intricate relationship between mosquitoes, Plasmodium, and humans, a life cycle diagram is an effective tool for visualisation and comprehension.

The life cycle of malaria

Malaria is a widespread disease that affects 97 out of 193 countries globally, primarily in Africa, Asia and the Americas. These regions are home to approximately 3.2 billion people, which accounts for nearly half of the world's population. In 2015 alone, there were 214 million reported cases of malaria, resulting in approximately 438 000 deaths. The majority of these cases (89%) and deaths (91%) occurred in Sub-Saharan Africa. These statistics highlight the significant burden of malaria, particularly in certain geographic regions.

Malaria symptoms resemble those of the flu and typically include fever and chills in the initial stages. It is important to note that malaria can be a life-threatening disease. While treatment options are available, prevention is a highly preferable approach. By taking preventive measures, such as using insecticide-treated bed nets, implementing indoor spraying programs, and taking antimalarial medications in high-risk areas, the incidence and impact of malaria can be significantly reduced.

Areas where malaria transmission is a risk

Prevention and control are best achieved by avoiding bites from the mosquito.

Individuals can prevent being bitten by mosquitoes by:

• avoiding being outside between dusk and dawn in countries where malaria mosquitoes are active: the species of the Anopheles mosquito that transmits malaria only flies at night

• wearing clothing that covers most of the body and treating exposed parts of the body with mosquito-repellent products

• sleeping under a mosquito net treated with an insecticide

• spraying the inside of the accommodation with insecticide.

For governments, strategies for malaria control are focused on controlling the vector. This can be achieved by:

• spraying insecticide inside buildings, including houses

• draining wetland areas to remove mosquito-breeding sites

• introducing fish which eat the larvae and pupae of the mosquito into ponds and other bodies of water

• pouring oil onto the surface of the water where mosquitoes breed, which stops the larvae from breathing and stops the adults from laying eggs.

Eradicating malaria entails the complete elimination of the malarial parasite from the population. Merely controlling the vector, such as mosquitoes, is insufficient; therefore, efforts must be directed toward finding methods to effectively eradicate the parasite itself. This involves developing interventions and strategies that specifically target and destroy the malaria parasite, ensuring its complete removal from human populations and ultimately achieving the goal of eradicating malaria as a public health threat.

The World Health Organization (WHO) currently promotes a global malaria eradication programme, aiming to eliminate malaria from all countries worldwide. During the first half of the 20th century, malaria was successfully eradicated from Western Europe and the USA. However, the primary challenge for the 21st century lies in achieving eradication in sub-Saharan Africa, where approximately 90% of all malaria cases occur. Efforts are focused on implementing effective interventions and strategies to address the specific challenges faced in this region and work towards eliminating malaria as a major public health concern.

Regrettably, there is a concern that global warming may contribute to the favourability of malaria transmission. Recent studies have indicated the re-emergence of malaria in the highland regions of Kenya, Colombia and Ethiopia, where it had been absent for several decades. However, another study, considering the complexities of climate change beyond just temperature rise, suggested that minimal changes in malaria distribution would occur. Understanding the intricate relationship between climate change and malaria transmission is crucial for implementing appropriate interventions to mitigate the potential impact of disease spread.

During the initial 12 years of the 21st century, advancements in malaria diagnosis, treatment and prevention have contributed to a 25% reduction in malaria incidence and a 42% decline in malaria-related deaths. Despite these improvements, the complete elimination of malaria through these methods alone is unlikely. Mosquito vectors are developing resistance to insecticides, and the malaria parasite is also becoming resistant to existing drugs. Furthermore, greater attention must be directed toward individuals infected with the disease but exhibiting no symptoms. It is evident that novel approaches for malaria control are imperative to address these challenges and make further progress in combatting the disease.

Be careful not to confuse malaria with bacterial diseases, such as cholera and typhoid. Bacteria breed in the water. Malaria is caused by a parasite, which breeds in an insect, which breeds in water.

Cholera Typhoid Infective bacterium (pathogen)

Vibrio cholerae Salmonella typhi or Salmonella paratyphi, which causes a less severe illness

Time before the onset of symptoms after infection

A few hours up to 5 days

6 - 30 days Symptoms Diarrhoea and vomiting Fever, abdominal pain with a skin rash Diarrhoea and vomiting are not uncommon Consequence Can be mild but can lead to dehydration and death 3-5% of infected people remain as carriers with no symptoms If untreated, fatal complications can arise Treatment Rehydration A vaccine exists Antibiotics A vaccine exists Occurrence in 2015 172 454 cases were notified to WHO from 42 countries, including 1 304 deaths Around 21 million a year with about 161 000 deaths worldwide