Drinking water
- Drinking water used should be safe for the consumption and acceptable.
- Safety implies, water is
- Free from impurities of all kinds that can be harmful for human health.
- Acceptable implies, water is
- Conforms to the taste consumers
- Must not be disagreeable to the consumers
- Physical quality
- Turbidity: indicates pollution; water should be free of turbidity
- Color: colored water is neither acceptable not suitable
- Taste & odor: should be agreeable
- Temperature: cool water is palatable and acceptable
- Chemical quality
- Water should not contain
- undesirable metals, like iron, zinc, copper etc
- Undesirable salts: chlorides, fluorides
- Undesirable gases like ammonia, methane, hydrogen sulphide
- Bacteriological quality
- Water may contain two types of bacteria
- Naturally occurring-
- these are usually non pathogenic
- Presence of these is of no public health significance.
- e.g.. Natural water bacteria, natural soil bacteria
- Fecal contamination –
- there origin is from intestinal tract of humans.
- They include pathogenic organisms and commensal organisms
- Presence of pathogenic organisms indicates public health significance
- Water intended for consumption should be free of all types of organisms.
Water purification on small scale
- It can be done in one of the following 3 ways -Boiling; Chemical disinfection; Filtering
- Boiling
- To be effective, the water must be brought to a rolling boil for at least 10 – 20 minutes.
- It kills all micro-organisms and make water sterile.
- It also reduces temporary hardness of water.
- But it offers no residual protection.
- Chemical disinfection
- Bleaching powder
- When freshly prepared, it contains 33% of available chlorine; but chlorine will be lost on storage and exposure to light, air and moisture
- 1000 L of water requires ≈ 2.5g of fresh bleaching powder.
- High test hypochlorite (HTH)
- If contains 60-70% of available chlorine and is stable.
- 1000 L of water requires 1g of HTH
- Potassium permanganate (KMnO4)
- Though powerful substance, it kills only cholera bacteria leaving viruses alive. it also imparts color to water making it unacceptable.
- Iodine:
- Though only 2 drops of 2% solution sufficient per liter of water, it is very costly and physiologically active. So not used frequently.
- Filtration
- Ceramic filters are used, like Pasteur Chamberland, Berkefeld and Katadyn filter.
- Essential past of filter is candle made of either porcelain infusorial earth.
- Some are coated with silver lining, which improves bacteria killing power
- However, many viruses escape through the pores of the filter.
- Filter candles are liable to be logged with impurities so they need regular cleaning by scrubbing with a hard brush in running water.
Disinfection of well
- First the volume of water in well is measured by repeated trial and error method to find depth of water and diameter (d) of well and using the formula [{pd2h*1000}/4]
- Then using Horrock’s apparatus, bleaching powder required is calculated.
- Then bleaching powder is mixed in a bucket of water in multiples of 100g. This is allowed to stand for one hour. Then precipitate is discarded and supernatant liquid is mixed well with the water in the well.
- Disinfection should preferably done daily, or at least alternate day
Collection and disposal of refuse
- What is refuse?
- Refuse may be defined as solid or semisolid waste matter produced in the normal course of human activities.
- Quantity of refuse produced depends on different countries, seasons, lifestyles, activities of people.
- Source of refuse:
- Garbage arising out of food catering, like vegetable peeling, fruits, food remnants
- Street refuse including decomposable and non-decomposable materials
- Composition of refuse
- Decomposable
- Includes organic material, of human or animal origin
- Food items, vegetable peelings, dead animals etc
- Non-decomposable
- Combustible: leaves, twigs, paper, etc
- Non-combustible: grit, ash, dust, pebbles, metal pieces etc
Refuse disposal
- Insanitary method of refuse disposal
- Hog feeding
- Pigs are excellent scavengers
- Though it is insanitary, it is cheap means in communities where refuse is disposed indiscriminately
- It contributes to soil & water pollution
- It can be source of hog-related zoonotic diseases
- Dumping
- Refuse is dumped openly in periurban areas.
- It is a source of breeding ground for flies, rodents
- Winds can scatter refuse and its bad odor over surrounding areas.
If water bodies lie closely, it can cause water pollution
- Sanitary method of refuse disposal
- Composting
- It is an integrated method of refuse disposal
- World over, there are some differences in methods of composting
- In India, refuse is composted with night soil, hence this offers convenient method of disposal of night soil & refuse.
- Sanitary landfill/ controlled tipping
- Most hygienic practice
- Refuse is first dried and condensed.
- Then it is laid with intervening earth partition to prevent nuisance due to fl breeding, rat harborage, offensive odors.
Excreta disposal
- Proper facilities for excreta disposal is very important at fair/ festivals
- Types of latrines
- Service types: they require manual servicing
- they are insanitary; hence cause environmental pollution
- Non-service types: they have in built or in situ disposal arrangements.
- They are sanitary; hence do not propagate diseases
Requirements of sanitary latrines
- Engineering requirement
- Site should be high and dry
- Area should not be too distant to prohibit its use not too close to well/ kitchen leading contamination
- Should be on a impervious floor, and away from soil to prevent hatching of hookworm eggs.
- Design should be suiting both adults and children
- Water seal and flush facility is desired.
- if latrine is done by excavating, then the pit should be suitably supported with bamboo rings etc
- It should be inaccessible to flies
Human requirement
- It should be accessible, acceptable, affordable and provide enough privacy
- It should conform to the defecation posture, cultural practices
- If need be, it should be installed separately for males and females.
- If people are used to open air defecation, they may resent using latrines, esp. if there is odor etc. it may be overcome by providing roofless superstructure.
Hygienic requirement
- Human excreta constitute primary source of diseases propagated by fecal oral route
- Disease may be transmitted directly through contamination of water or indirectly thorough food contaminated by infected fingers, flies, soil or water.
- Sanitary latrine
- Prevents soil and water pollution
- Prevents diseases originating from fecal oral route
- Prevents access to flies, hogs, dogs etc.
- Health education to the community is required to ensure utilization of the latrines so constructed.
Accommodation of pilgrims
- Accommodation should be provided such that there should not be overcrowding
- Overcrowding often leads to easy transmission of respiratory and/or skin infections.
- An adult person should have at least 70-90 ft2 while children b/w 1-10 years should have 50 ft2. space provided should never be <50 ft2
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