3.2.2. Visible Parameters

This information can be put it in a different format, so we have to step back, okay. So if somebody comes and asks is the water contaminated, is water safe to drink? So your answer cannot be, your absolute final answer can be okay give me a month's time, I will analyze whether it contains all the one lakh chemicals that we know that are that exist in nature and then I will tell you in a month’s time, that is not acceptable, people won’t wait for that long. So you need a quick answer. What is this quick answer, quick answer can never be a detailed answer, it has to be a short answer, but it gives you partial information, whether you. So we do whenever we do such things, we need a quick answer, we need what is called as Screening.

In water quality assessment, when someone asks if water is safe to drink, we don't have the luxury of time to conduct extensive tests. Instead, we need a quick response that gives a preliminary indication of water quality, often referred to as 'Screening'. This screening is not comprehensive but offers partial insights into whether the water may be good or bad. Essentially, it's about making a fast assessment based on visible characteristics instead of waiting for detailed chemical analysis.

Imagine you're at a restaurant and the waiter brings you a glass of water. You don't have time for a laboratory test, so you quickly check if the water is clear, smells good, or seems dirty. If it looks contaminated, you wouldn’t drink it without a second thought. That initial, quick evaluation is similar to screening in water quality testing.

By just looking at it, can you screen a water sample? Keep in mind all the discussion we had in the previous slide, where we talked about chemicals and all that, but when we look at water quality itself, what do you look for? So our water quality again? When somebody gives you a water sample, so what is the first question you ask them? When somebody says please tell me if it is good water? So your question, what is your follow-up question?

When assessing water quality visually, the first indicators are its appearance. You may ask about the water's source, whether it's meant for drinking, which is the highest quality requirement. Important visible indicators include: the water’s clarity (is it clear or turbid?), color (is it colorless?), and odor (does it smell bad?). If the water is colored, turbid, or smells unpleasant, these are red flags indicating that it might not be safe to drink.

Think about choosing a fruit at the grocery store. You wouldn't pick a bruised or overly soft apple, even before tasting it. Similarly, when looking at water, its clarity and smell tell a lot about its potential safety before you even sample it.

So drinking water, what will you look for in drinking water? When somebody gives you a glass of water, when will you not drink the glass of water? If it is coloured, if it is turbid. Then smell, or we call it as odor. If you see any of these, that would make you hesitate to drink it.

For drinking water, specific visible parameters are crucial. If the water is colored, this indicates the presence of impurities, while turbidity means it’s not clear, and thus, likely contaminated. If it has an unpleasant odor, it may indicate further hidden contaminants. These factors help classify the water as potentially unsafe to drink, highlighting the need for further testing.

Picture this: You are at a friend's house, and they offer you a glass of water. You notice it's muddy and has a strange smell. Just like you'd avoid eating spoiled food, you instinctively know to avoid drinking that water, as it likely contains harmful substances.

Dissolve is in the structure of the water and I think it does not form any precipitate, it is dissolved. Clean, clear. Salt water for example, if you dissolve salt or sugar, it is dissolved. You will see a clear solution.

In water quality, it's important to distinguish between dissolved substances (those that are mixed in at the molecular level, like salt in water) and suspended solids (which float or settle in the water, like sand or dirt). Dissolved substances remain clear and do not form visible particles, while suspended substances can cloud the water and indicate pollution.

Consider how sugar dissolves in tea. When sugar is completely dissolved, you can't see it, but it affects the sweetness of the tea. In contrast, if you stir in sand, you will see it settle at the bottom—this is similar to how suspended solids act in water.

So one of the water quality parameters is we call it as total dissolved solids. See the word solids is a very it is a misnomer here, it is not an insoluble solid, it’s a solid. People have used this term, it is called as TDS and the other one is total suspended solids TSS.

Total Dissolved Solids (TDS) includes all dissolved substances in water, both organic and inorganic. Even though the term 'solids' suggests they might be undissolved, here it refers to everything that is not visible as a solid precipitate. Total Suspended Solids (TSS) are the solid particles that do not dissolve in water. Together, both parameters provide insight into water quality and help assess its safety for different uses.

Think of clear soup and a chunky soup. The clear soup may have many flavors dissolved in it, making it rich in taste (like TDS), while the chunky soup holds visible pieces like vegetables and meat that add texture (like TSS). When evaluating water quality, both aspects are essential to determine how safe or healthy the water is.

--