Keywords

1 Introduction

The lack of access to clean water is a global issue that affects all countries. The strong human desire to improve living standards has inevitably resulted in water pollution, with cumulative efforts and activities establishing as heavy industrial development and incessant urbanization, leading to progressive pollution of aquatic system [1,2,3,4]. When it comes to drinking, irrigation of crops, waste disposal, transportation, recreation, irrigation of crops, and industrial production, humans are utterly dependent on renewable resources of freshwater. The quality and quantity of water that can be used to placate human necessities are already threatened in many parts of the biosphere due to rising water usage, growing population, climate change and a rising water usage, the gap between freshwater availability and demand will worsen over the next century. About 80% contamination of Indian water resources, according to estimates by WHO, is caused by inhabited refuse. Water system management issues could have a substantial impact on the supply of drinking water [5, 6]. Industrial waste is the main basis of water contamination. Wastewater from various industries is disposed of in the water without being properly treated [2]. Monitoring water quality is a vital component of environmental research and public health. It entails evaluating a range of physical, chemical, and biological factors to make sure that water is suitable for diverse uses, from supporting aquatic life to safe human consumption [7]. Temperature, turbidity, and color are some examples of the physical parameters. Aquatic creatures’ biological activity and growth are directly influenced by temperature. Water clarity, or turbidity, can influence how aquatic plants synthesize their food and also reveal the presence of microbes. Minerals and organic debris that are dissolved in the water can be identified by looking at the color of the water. pH, conductivity, dissolved oxygen, hardness, and the presence of specific ions like nitrates, phosphates, and heavy metals are examples of chemical parameters. The solubility and toxicity of substances in the water can be influenced by the pH of the water, which is a measurement of its acidity or alkalinity [8]. Water's conductivity, a metric of how well it conducts electricity, is inversely proportional to its ion concentration. The life of aquatic species depends on the presence of dissolved oxygen. The usefulness of water for home and industrial usage can be influenced by its water hardness, which is determined by the amount of calcium and magnesium ions present. Heavy metals, phosphates, and nitrates can all be signs of pollution and provide health dangers [9].

A change in the underlying sediments’ and aquifers’ chemical makeup also affects the variation in water quality. Surface sources like canals, lakes, dams, and rivers provide around one-third of the world's drinking water needs. Water is used in some way or another by an organism's chemical and physiological processes. In numerous aspects of existence, water is crucial. In order to research numerous physicochemical water characteristics including B.O.D. (biochemical oxygen demand), WQI (water quality index), D.O. (dissolved oxygen), Eutrophication, heavy metal, alkalinity, etc., water samples from rivers and lakes provide an appropriate platform. Many scientists have occasionally studied the physicochemical properties of water bodies. The physicochemical features will also aid in the continuation of eco-biological impact research, the detection of pollution sources, and the beginning of remedial action procedures for polluted water bodies [10]. Numerous scholars in India have studied the physicochemical and biological properties of reservoirs and rivers. Since a variety of physical and chemical elements can combine to affect primary production levels, which in turn affect total biomass and trophy structure across the aquatic food web, water quality must be taken into account when evaluating wetland habitat.

Gaining a deeper understanding of these factors will help us manage our water resources more effectively, reduce risks, and guarantee the well-being and security of our communities and ecosystems. The function each of these parameters plays in determining the quality of the water, the variables that affect them, and the effects of their imbalance will all be covered in more detail in the sections that follow.

2 Analysis of Water Quality

Before using water for drinking, residential, industrial, or agricultural purposes, it must first be tested. Different biological, physical, and chemical factors must be used to test water. The only factors considered when selecting water testing parameters are the envisioned use of the water and the level to which its purity and quality are required [11,12,13,14]. Different kinds of microbiological, dissolving, suspended, floating, and bacteriological pollutants are present in water. Physical tests should be conducted to evaluate the substance's odor, color, temperature, pH, TDS, turbidity, and further physical characteristics. Chemical tests should be conducted to evaluate the substance's COD, BOD, alkalinity, hardness, DO, and other characteristics [15]. Water must be verified for heavy metal trace, organic, and metal contaminants like pesticide scum in order to obtain more and more pure, high-quality water. It goes without saying that potable water must satisfy all of the required parameters during tests and contain the necessary amount of minerals [16, 17]. Only in wealthy nations are all these requirements properly checked because there are very few organic and heavy metal pesticide contaminants in water, necessitating extremely analytical equipment and skilled labor. To monitor the water quality, a variety of physical–chemical parameters must be used.

2.1 Temperature Measurement

Using a digital thermometer, the temperature is determined by dipping the thermometer in the sample and recording the result [18]. Temperature is the degree of heat or cold in an aquatic organism’s body, whether it is in water or on land. Despite having cold blood, fish experience body temperature changes in response to their environment. These changes have an impact on the fish's physiology and metabolism as well as its production. The microbiota’s rate of metabolic activity as well as their rate of respiration both increase with temperature because of the rise in oxygen demand. It also results in increased ammonia levels in water and decreased oxygen solubility. However, with prolonged ice cover, chemicals such as carbon dioxide, methane, and hydrogen sulfide can build up to dangerous levels and affect the health of fish [19].

The accumulation of dangerous gases such carbon dioxide, methane, and hydrogen sulfide under varied lengths of ice cover is shown in Figs. 1 and 2. Figure 1 shows how chemical concentrations alter as ice cover duration lengthens. As seen in the image, there is a definite positive association between the quantity of these dangerous substances and the length of the ice cover. In particular, the data points point to a significant rise in chemical concentration following a specific critical period of ice cover. This suggests that a protracted ice cover may eventually cause a buildup of these compounds to levels that are harmful to aquatic life. Figure 2, on the other hand, depicts the condition of fish populations under various chemical concentrations brought on by various ice cover durations. The graph clearly shows that fish health drastically declines when chemical concentrations increase, a scenario brought on by prolonged ice cover. The need of preventing protracted ice cover scenarios is highlighted by this research in order to protect aquatic biodiversity and fish health.

Fig. 1
2 world maps depict the land surface temperature and groundwater temperature. The countries in the world map are shaded from a light to a dark shade with a color indicator and range from less than minus 5 degrees Celsius to 40 degrees Celsius.

Decadal average (2005–2014) of global shallow groundwater and land surface temperatures [19]

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Fig. 2
2 scatterplot plots of land surface temperature versus groundwater temperature. It depicts an increasing regression line and points in a cluster plotted on it.

a Correlation between land surface and groundwater temperatures; b Comparison of estimated and measured groundwater temperatures [19]

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2.2 pH Measurement

The pH scale, which determines how acidic or alkaline a solution is, fluctuates depending on the geology, contaminants, and climate of the area. For instance, locations with granite bedrock may have more acidic water than those with carbonate bedrock. Additionally, pollutants and dissolved gases can affect pH. Although drinking water is frequently supplemented with minerals and has a pH of 7, pure water is inherently more alkaline. The World Health Organization recommends drinking water with a pH of 6.5–8.5. Beyond this range, water may provide health problems because extremely low pH can lead to corrosion and the release of metal ions from pipes, while extremely high pH can occasionally result in skin and eye irritation [20]. Due to the inclusion of minerals, bottled mineral water like Bisleri may have a pH slightly higher than 7. It's generally accepted that keeping a balanced pH in drinking water is essential for health, despite occasional claims to the contrary.

A key indicator of water quality, pH, is regulated by a variety of environmental conditions [21]. The regulation of pH is significantly influenced by dissolved materials, especially minerals and gases. For instance, the water frequently contains significant levels of calcium and magnesium in areas with limestone or dolomite bedrock, resulting in a more alkaline pH [22]. Similar to this, regions with a lot of organic matter that produces CO2 or with volcanic activity may have more acidic water because dissolved CO2 causes carbonic acid to develop [23]. Water pH is impacted by pollutants as well. Water's pH can be dramatically lowered by acid rain, which is caused by the atmospheric deposition of pollutants including sulfur dioxide and nitrogen oxides [24]. Heavy metals and other compounds that might change water pH and potentially damage aquatic life as well as degrade water quality are frequently present in industrial effluents [25]. Understanding the variables that affect water pH and keeping an eye on them are therefore essential for maintaining the highest possible level of water quality. This intricacy highlights the necessity for thorough water evaluation methods that can take these various factors into account.

2.3 DO Measurement

Determining the amount of dissolved oxygen in a river is crucial since aquatic life there depends on it and needs at least 4 ppm of DO to survive [8, 18, 26]. DO tests are carried out to confirm this. The Digital Dissolve Oxygen Meter is used to measure the DO test at the location of the sample collection. When measuring DO on-site, the results are correct, but if DO is measured later, the results will alter due to changes in the atmosphere and temperature [10, 14].

2.4 BOD Measurement

The BOD is a measurement of how much total dissolved oxygen is used by microorganisms during the biodegradation of organic materials, such as sewage or food particles. Rural ponds may have an excessive amount of phosphate, cow waste, and domestic sewage from non-point sources, which all contribute to a high organic load and a higher BOD level [27].

2.5 COD Measurement

Chemical oxygen demand, which is typically combined with biological oxygen demand, is a measure of the amount of organics in water (BOD). The COD is a measurement of the amount of organic matter in a sample that can be oxidized by a potent chemical oxidant [28,29,30,31]. The COD is frequently employed as a gauge of the organic and inorganic materials’ susceptibility to oxidation in water bodies, industrial plant effluents, and sewage discharges [32]. As a result, the COD is an accurate indicator for determining the degree of water pollution (Fig. 3). As organic and inorganic matter concentrations rise, so does the COD of water [33, 34]. According to Garg [35], the COD concentration in Ramsagar reservoir ranged from 3.600 to 17.400 mg/l.

Fig. 3
2 illustrations depict the influence of predation on sprat population stages. It depicts sprat population that decreases over time depicted in two cycles.

Community conditions resulting in cod Allee effect: influence of predation on sprat population stages [36]

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2.6 Carbon Dioxide Measurement

Unrestricted carbon dioxide, an exceedingly soluble gas in water generated by animal respiration, serves as nature's primary source of carbon. It can exist in water as dissolved or bound bicarbonate or carbonates in coral reef habitats, the earth's crust, and limestone. The pH of any system, especially those with inadequate buffering, is reduced when carbon dioxide is dissolved in water. This pH decrease can be harmful to aquatic life [37].

2.7 Alkalinity Measurement

Alkalinity, a measurement of the inclusive concentration of bases in pond water that includes dissolved calcium, magnesium, and other compounds as well as, bicarbonates, hydroxides, borates, phosphates, and carbonates, is the volume of water to engross variations in pH. Alkalinity is primarily increased by lime leaching from cement ponds or calcareous rocks, photosynthesis, sulfate reduction, and de-nitrification and it is primarily decreased or consumed by sulfide, respiration, and nitrification [38], as well as to a lesser extent by evaporation and decomposing organic matter. However, in case of insufficient alkalinity, even minor bit of acid might source a large pH change.

2.8 Nitrite-N (NO2-N) Measurement

An intermediate in the transformation of NH4+ or NH3 into NO3, nitrite, is a by-product of oxidized NH3 or NH4+. Nitrification, which is carried out by the system's naturally occurring highly chemo-autotrophic bacteria, aerobic, gram-negative, completes this process. Due to the rapid nature of the dialogue, large nitrite amounts are not frequently seen. The “brown blood illness” is a condition where high amounts of the substance do, however, result in hypoxia brought on by the hemoglobin in fish blood becoming inactive [39]. Boyd [40] asserts that less than 0.3 mg/l of nitrite is the ideal level for aquaculture. The concentration of nitrite at cage stations was greater than the standard permitted value due to the influence from fish waste and more feed, according to research [41,42,43,44,45,46,47] that found the concentration of nitrite-N lay in the range of 0.001–0.28 mg/l in cage culture systems. It has been discovered that a higher less dissolved oxygen, more ammonia, and pH can make it more poisonous.

2.9 Nitrate–N (NO3-N) Determination

Nitrate is created via the process of nitrification, which is the oxidation of NO2 to NO3 by aerobic bacteria. De-nitrification of nitrate that aquatic plants cannot directly absorb occurs in anaerobic sediments [48]. According to Garg et al. [35], the ideal nitrate content for aquaculture is between 0.2 and 10 mg/l. Sewage and other pollutants high in nitrates can also contaminate surface water. Drinking water with higher nitrate content is harmful [49]. The Environmental Protection Agency (EPA) has determined that 10.00 mg/l of nitrate is the maximum contamination level (MCL) for water to be used for drinking purpose [50]. The concentration of nitrate in receiving waters is significantly impacted by runoff from farming operations and waste disposal sites. The usage of fertilizers on farms may have contributed to receiving streams’ elevated nitrate levels through leaching and surface runoff during heavy rains [34].

2.10 Ammonia (NH3) Determination

Ammonia is a consequence of the protein metabolism that fish harvest, as well as the breakdown of bacterial of biological waste like dead planktons, food scraps, and manure. Both ionized or unionized and ammonia are referred to as “total ammonia,” yet only the unionized form (NH3) is extremely toxic [36].

2.11 TSS Measurement

Total suspended solids, also known as non-filterable solids, are those solids that are retained by a filter with 1-micron holes. By running a known volume of sewage sample through a glass fiber filter equipment and weighing the dry residue that remains, their amount may be calculated [51].

2.12 Total Dissolved Solids (TDS) Measurement

Total dissolved solids, also known as filterable solids, are those solids that are not retained by a filter with 1-micron holes. By running a known amount of sewage sample through a glass fiber filter equipment and weighing the dry residue that remains after boiling the filtrate sewage, their quantity may be calculated. TDS is made up of organic and inorganic materials that are suspended in water [52]. The taste and potability of water can be impacted by high TDS [53]. TDS levels in drinking water should be measured using a conductivity metre and should be between 500 and 1000 mg/l according to WHO. TDS levels can be managed with treatments like reverse osmosis [54].

2.13 Measurement of Turbidity

As soon as you can after the sample is taken, determine the turbidity. Before examination, gently stir all samples to achieve a representative measurement. If sample preservation is not possible, start the analysis right away. If storage is necessary, refrigerate or cool to 4 °C to reduce the amount of microbial degradation of solids. For the best outcomes, test the turbidity right away without changing the pH or temperature of the original sample. A digital turbidity meter is used to measure turbidity. This was calibrated using a standard NTU [51, 55].

2.14 Heavy Metals Measurement

Each sample of acid-digested water weighed 100 cm3 and was placed in a beaker. The beaker was then placed in a 70 °C oven to condense the water to 50 cm3. Using an atomic absorption spectrometer, the concentrations of Co, Cu, Cr, CD, Zn, PB, and Ni in each sample of water were measured (AAS: AAS: LABINDIA: AA-7000) Prior to analysis, AAS required phase of acid digestion, which was accomplished by exposing the samples to concentrated HNO3 [34]. Samples are digested using the methods endorsed by the American Public Health Association (APHA). The suggestions in the instruction manual were used to determine the instrument settings (IO).

2.15 Chlorides Measurement

Chlorides, which are often present as sodium chloride, alter the flavour of water [53]. Both pipes and vegetation may be harmed by presence of excess chlorides [56]. Titration techniques or ion chromatography are frequently used to determine the concentration of chloride [52]. A 250 mg/l limit is advised by the WHO [53]. Chloride levels can be controlled by reducing industrial effluents and recycling [54].

2.16 Biological Indicators

The presence of specific microbes, algae, and other lifeforms can reveal information about the quality of the water. E. coli is frequently tested for because its presence suggests fecal contamination [53]. Eutrophication can result from an algae bloom, which is frequently brought on by too many nutrients (such phosphates) [57]. Chemical and biological testing work together to offer a complete picture of the water quality [4, 6].

2.17 Index of Water Quality (WQI) Measurement

The WQI is premeditated in three steps. Each criterion was given a weight (Wi) in the first phase based on its relative significance to the overall quality of water intended for consumption. Nitrate has been given a maximum weight of 5 due to its significant role in determining the water quality [58]. The relative weight is computed using Eq. 1 in the second step.

$${W}_{i}=\frac{{w}_{i}}{\sum_{i=1}^{n}{w}_{i}}$$
(1)

where n is the number of parameters, relative weight is denoted by Wi, and wi represents the weight of each parameter. The parameter's calculated Wi values are provided in Table 1.

Table 1 Chemical parameters and their relative weight [59]
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In the third stage, by dividing each parameter's concentration in each water sample by the relevant standard, according to the BIS specifications, and multiplying the result by 100, a quality rating scale (qi) is obtained for each parameter (Eq. 2)

$${q}_{i}=\left(\frac{{C}_{i}-{C}_{io}}{{S}_{i}-{C}_{io}}\right)\times 100$$
(2)

where Si is the BIS-recommended standard for Indian drinking water in mg/l for each chemical parameter and Ci is the concentration of each chemical parameter in every single water sample in mg/l. The parameter's optimal value in clear water is Cio. With pH, qi is equal to (Ci − 7)/(Si − 7)100 and Cio is equal to 7. For the remaining parameters, the optimal value is 0.

Each parameter's sub-index (SI), which is utilized to calculate the WQI in accordance with Eqs. 3 and 4, is first determined in order to calculate the WQI.

$${\mathrm{SI}}_{i}={W}_{i}\times {q}_{i}$$
(3)
$$\mathrm{WQI}=\sum_{i=1}^{n}{\mathrm{SI}}_{i}$$
(4)

The ith parameter's subindex is SIi. The estimated WQI values are classified into five categories in Table 2.

Table 2 Classification of water quality based on WQI value [59]
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The five categories range from “good water” to “unfit for drinking water,” according to the computed WQI values (Table 2). The WQI has an inter-seasonal range of 28–267, with 24% of water bodies rated outstanding in the pre- and post-monsoon seasons and 18% rated excellent during the monsoon season. Approximately 62%, 58%, and 60% of water bodies are in good quality during the monsoon, pre-monsoon, and post-monsoon seasons, respectively in pre-monsoon, monsoon, and post-monsoon seasons, respectively. 14, 16, and 12% of water bodies were found to be poor water bodies in the respective seasons. The remaining 6, 2, and 4% of water bodies were very poor water bodies in aforesaid seasons. 16 and 48% of water bodies are in excellent and good water bodies throughout the monsoon and post-monsoon seasons. Limits for the physicochemical properties of lake water in India are shown in Table 3.

Table 3 Physical and chemical features of Indian lake water [60]
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3 Advantageous and Limitations of Water Quality Evaluation and Treatment Methods

Numerous evaluation and treatment techniques have been created throughout the years in the quest to monitor and manage water quality. While each of these approaches has its own advantages and drawbacks, it is important to be aware of both in order to choose the approach that will work best in a certain circumstance. The biological, chemical, and physical testing approaches that are frequently employed in water quality evaluation and treatment are examined in this section along with their benefits and limitations [61]. By doing this, we intend to provide a thorough grasp of these techniques, permitting more informed choices about the management of water quality.

3.1 Physical Testing Methods: Benefits and Limitations

Advantages:

  1. 1.

    Physical tests can frequently be performed on-site and offer fast findings.

  2. 2.

    These tests can often be carried out more easily and affordably than chemical or biological ones.

Disadvantages:

  1. 1.

    Limited Information: Physical examinations can't tell you anything about particular chemical or biological pollutants.

  2. 2.

    Subjectivity: Some physical tests, such as smell and color, can be a little subjective and may not give accurate quantitative information.

In order to obtain a thorough understanding of water quality, each of these techniques should preferably be utilized in combination.

3.2 Chemical Testing Methods: Benefits and Limitations

Advantages:

  1. 1.

    Specificity: Chemical analyses can locate particular contaminants, enabling focused responses to contamination.

  2. 2.

    Quantitative Information: These tests offer quantitative information that can be used to determine conformity with rules and specifications.

Disadvantages:

  1. 1.

    Expensive: Testing for a wide range of potential contaminants can be expensive when doing chemical analyses.

  2. 2.

    Point-in-Time Data: These tests offer a snapshot at a particular moment in time, and it's possible that they don't accurately capture changes in water quality over time.

3.3 Biological Testing Methods: Benefits and Limitations

Advantages:

  1. 1.

    Sensitive Indicators: Some species may be exceptionally sensitive to particular pollutants, making them reliable markers of harmful chemicals.

  2. 2.

    Long-term monitoring: Biological testing is helpful for long-term monitoring since it offers a snapshot of water quality across time rather than only at one particular instant.

  3. 3.

    Threats other than chemical pollutants can be found through biological testing: These include threats like temperature fluctuations, habitat damage, and more.

Disadvantages:

  1. 1.

    Requires professional expertise: Accurate identification and interpretation of biological indicators can be time-consuming and require professional expertise.

  2. 2.

    Seasonal variations make it challenging to compare results obtained at various times of the year since biological indicators can alter with the seasons.

3.4 Water Quality Index (WQI) Method: Benefits and Limitations

Advantages:

  1. 1.

    Simpleness: The WQI method's biggest benefit is the straightforward nature of the procedure. It reduces complicated water data to a single, simple number. With the use of this one number, the general public and decision-makers can be properly informed on the water quality.

  2. 2.

    Comprehensive: The WQI approach provides a comprehensive snapshot of the water quality by accounting for a wide range of characteristics. When assessing the effects of particular actions or tracking changes over time, this can be helpful.

  3. 3.

    Comparative Evaluation: WQI enables users to compare the water quality of one body of water to another or to the same body over time. This can assist in locating issue regions or water quality trends.

Disadvantages:

  1. 1.

    Lack of Specificity: Despite offering a helpful overall evaluation, the WQI does not draw attention to particular contaminants or characteristics. Even in the presence of high levels of a particular pollutant pollution, a location may still have a positive WQI if all other factors fall below permissible limits.

  2. 2.

    Equal Weight: WQI anticipates that all parameters will be given equal weight. This can be a drawback because some criteria might be worse for the environment and human health than others.

  3. 3.

    Variation in Standards: It is difficult to apply a global WQI since different countries and regions have different acceptable limitations for the criteria they utilize.

4 Physicochemical Review of Some Water Samples from India

The study of physical–chemical parameters is crucial to obtaining a precise understanding of the water quality, and it allows us to compare the results of various chemical and physical parameter values with reference values (Table 3). Here is a brief summary of some previous research studies. Pulp and paper sector effluents are one of India's most polluting industries, according to Tripathi et al. [62]. Small and large pulp and paper mills use several procedures that produce effluents with drastically varying physical–chemical characteristics due to their disparate production capacities and raw material sources. To diminish the impact of various pollutants on the environment, before being released into the drainage channel, such contaminated effluents must undergo sufficient treatment. Based on the findings presented here, it can be stated that the effluent emitted from both paper industries is extremely contaminated and exceeds the limits set by Indian regulatory agency norms. Furthermore, it is claimed that the pollutants produced at various stages of the paper manufacturing process can be reduced either by replacement of some current bleaching and pulping techniques with ECF (Elemental Chlorine Free bleaching), bio-pulping, TCF (Total Chlorine Free bleaching), bio-bleaching, and ozone bleaching or by treating the effluent with physical, biological, or chemical methods. This monitoring research of pulp and paper mill effluent collected from wood-based and agro-based sources resulted in the creation of a data bank that may be used to successfully anticipate their toxicity and implement appropriate management. Agrawal et al. [63] concluded that the water in the Bihar River can perform as a good habitat, provide educational data, and aid in understanding water features. The pH value suggests that the alkaline water in May have resulted from the high temperature, which suggests that CO2 is soluble in the water. The Bihar River's Baba Ghat's water quality metrics, including alkalinity, total hardness, chloride ion, pH, BOD, COD are all well within the acceptable range, according to the analysis. Consequently, appropriate methods should be developed. According to research by Kaur et al. [64], the majority of freshwater bodies worldwide are becoming contaminated by human waste, industrial waste, sewage, agricultural waste, and religious practices like idol immersion. The Central Pollution Control Board [65] has created a thorough set of regulations regarding the act of immersing idols in oceans, lakes, and rivers (Guidelines for Idol Immersion, CPCB 2006). These regulations outline and define the function of state pollution control boards in evaluating the water quality of aquatic bodies and categorizing them according to specific physiochemical parameters. If these recommendations are followed and put into practices, the quality of the river's water after idol immersion could significantly improve. Khan et al. [66] assert that the most crucial metric for determining the water quality is DO, which was discovered to be Nil at seven places despite being necessary for all aquatic creatures’ metabolism. Altaf and Saltanat [67] came to the conclusion that water temperature and water chemistry are the primary influences on phytoplankton dispersal, chloride, transparency, dissolved oxygen, alkalinity, TDS, and CO2. Hardness and Conductivity, on the other hand, have less of an impact on the distribution of phytoplankton groups. Rani Lake water displays low high COD, BOD, DO, hardness, turbidity, alkalinity, chloride, TDS, nitrate, and phosphate during 2008 and 2009, according to evaluations done by Mishra et al. [68]. These parameters’ values were discovered to be over the allowable limit (IS: 10500). A higher pH number implies that the water is slightly alkaline. The results unambiguously show that sewage discharge and other anthropogenic activities have caused this lake to become contaminated and entropic in character. The amount of oxygen utilized during aerobic processes of organic material degradation brought on by microorganisms is measured by biological oxygen demand. Therefore, the BOD provides details on the proportion of an organic substance in a sample of water that can be converted biologically. As a result, it is necessary to take into account how susceptible certain materials are to oxygen oxidation. The pre- during and post-immersion activities yielded the ranges of 1.4–35, 4–55, and 3.3–38 mg/L. At Site-7, the immersion period produced the highest BOD value (Majnu Ka Tila). Analysis was also done on the COD, which is frequently used to estimate indirectly how many organic chemicals are present in water. COD is a helpful indicator of water quality because the majority of its applications estimate the volume of organic contaminants present in wastewater or surface water (such as lakes and rivers). As indicated by a number of researchers [69,70,71,72,73], the value of COD in conjugation with BOD is beneficial in determining the hazardous circumstances and existence of physiologically resistant organic compounds.

5 Conclusions and Recommendations

The water quality of rivers and lakes has declined as a result of all the aforementioned effects. It provides a hint for municipal authorities to create effective management plans. The main factors influencing temperature variation are atmospheric temperature and weather. The industrial effluents that were released may have contributed to the pH decrease in Indian water bodies. This outcome is consistent with prior scientists’ reports. The decrease in water volume due to rapid evaporation at high temperatures, high loadings of organic compounds, chlorides, detergent, and other pollutants are all responsible for the increase in hardness. Low levels of DO as a result of wastewater discharge from enterprises that were discharging some biological wastes that demanded a lot of oxygen. An important factor that is frequently used to estimate the pollutant load of wastewater is biological oxygen demand. The purpose of the BOD test is to quantify the quantity of carbonaceous matter that is biochemically oxidized. Values of BOD were caused by a faster rate of organic matter decomposition with turbidity, at a higher temperature and slower water current. A test called chemical oxygen demand is used to gauge how polluting household and industrial waste is. This provides important information regarding the possibility for pollution from home sewage and industrial effluents. Many aquatic zones in India have high COD value, which shows that industrial effluents released by industrial units are mostly to blame for the pollution there. Therefore, it is crucial to check the water's purity using the several criteria listed above before utilizing it.