System of sanitation

System of sanitation in the hygienic means of maintaining proper health through the prevention of human contact with hazards of wastes by proper treatment and disposal of solid and liquid wastes.

Human use the resources of the earth and waste products are produced. These wastes are generated by domestic, commercial and industrial activities. If these wastes are not carefully disposed then there is water, soil and air pollution.

Sanitation has played a great role in maintaining a healthy life and environment for the living of human and other creatures on the earth.

System of Sanitation

1.Conservancy System

This system is also known as a dry system. In this system, various types of refuses are collected, conveyed and disposed off separately by different methods. Garbages and refuses of a town are collected in dustbins placed beside the road.

The collected garbages and refuses are conveyed by trucks to the point of disposal. All the non-combustible portion of the garbage like sand, silt, clay, etc are used for filling the low-level areas while the combustible portion of the sewage like dry leaves, waste paper, broken furniture, etc are burnt.

Human excreta are collected separately in privies or conservancy latrines and are carried by human agencies.

System of sanitation

Advantages of Conservancy System

  • It is cheaper in the initial cost.
  • Quality of sewage reaching at the treatment plant before disposal is low.

Disadvantages of Conservancy System

 

  • Burning of garbage, dry refuse, etc cause environmental degradation and pollution.
  • Decomposition of sewage causes unsanitary conditions on public health.

2. Water Carriage System

As the conservancy system produces sanitary as well as aesthetic problems. So, after a number of experiments; water carriage system is determined best.
In this system, water is the main system of disposal of the waste.

System of sanitation

Advantages of water carriage system

  • More hygienic method.
  • The unusual water supply is sufficient and no additional water is required in water carriage system.
  • This method does not depend on manual labour at any time except when the sewer gets blocked. 

Disadvantages of water carriage system

  • Not suitable for the area having less water
  • Maintenance cost is high.
  • High initial cost.

Water Distribution System

The process of distributing treated water to the consumers is called water distribution system. The distribution system includes pumps, reservoirs, valves, water meter, pipe fittings, etc. The cost of the distribution system is about 40-70 % of the total of the entire scheme.

The aim of a good water distribution system is to supply water to all the consumers whenever required in sufficient quantity with required pressure without any leakage.

1.Requirements of good water distribution system

  • The system should be economical to maintain and operate.
  • Sufficient water should reach to all consumers.
  • It should be able to draw enough water during an emergency like fire fighting.
  • The system should be watertight and leakage should be least as possible.
  • Any types of contamination of water should not occur during the distribution.
  • It should not be laid below the sewer lines as far as possible.
  • The system should have required pressure that it conveys water adequate but the pressure should not be high causing the bursting of pipes and fittings.
  • The distribution layout should be such that it should supply water even during repair and maintenance time.

2.Methods of water supply of Water Distribution System

There are two types of supplying water.

i. Continuous system

ii. Intermittent system

  1. Continuous system
    This is the best method in which the water is supplied to the community during all 24 hours of a day.

    In this system, a sufficient amount of water is always available for consumers to use and also for an emergency like a fire fighting. Due to the continuous circulation; water remains fresh but the losses will be more if there are leakages in the system.
  2. Intermittent System
    If adequate water is not available, the whole community is divided into several zones and water is supplied in each zone for a fixed time in a day or alternate days. The water flows in the consumer’s tap at certain intervals. So, it is called intermittent system.

3.Methods of Water Distribution System

For efficient distribution, it is required that water should reach to every consumer with the required rate of flow. Therefore the same pressure in the pipelines is necessary which should force the water to reach every place. The distribution systems can be classified as follows:

a. Gravity System

When the distribution reservoir is located at a higher elevation than the target community; then water can be supplied with the gravity flow. This method is much suitable when the source is the river or impounded reservoir at sufficient height than the target community. Usually pumping water is not required at any stage of this type of distribution.

water distribution system

Advantage of gravity method

  • No energy is required to operate the system as water is conveyed by gravity.
  • No pump is required.

Disadvantage of gravity method

  • Not applicable in plain or flat terrain like terai where an elevation source of water supply is not available.
  • Water loss by leakage is comp[aritively higher as the system remains under constant pressure.

2. Pumping System

In this system, water has to be pumped and then directly send to the public. In the pumping system, a number of pumps are established and only some of them are always used. Some of the other pumps are installed for emergency causes like fire hazards, peak water demand, etc. This method is suitable if the source is not very high than the target community.

Water Distribution System

However, this system of distribution becomes very expensive for long term use. Also, if electric pumps are used, the water may be insufficient when the power fails. So most commonly diesel pumps are managed for an alternative. This method has no problem with the pressure and maintaining the head at the consumer’s tap.

Advantages

  • Water can be pumped only when required.
  • Low water loss due to leakage.

Disadvantages

  • Break down of system occurs if power fails.
  • Maintenance and operation cost is high.
  • During pumping hours, the inflow of water through leaks may cause water contamination.

3. Dual System

This method is also called a combination system of gravity and pumping system. The pump is connected to the mains as well as to an elevated reservoir.

Water Distribution System

In the beginning, when demand is small; water is stored in the elevated reservoir but when demand increases then the flow on the distribution system come from both the pumping station as well as elevated reservoir. As in this water pumps from two sources name from reservoir and pumping system. So it is called the Dual System.

Video

( Note:

Break Pressure Tank

There is a certain working pressure of pipes and this limit should not be crossed. Due to water flowing in the pipe, hydrostatic pressure is exerted on the joints and fittings of pipe. If this pressure exceeds the allowable working pressure of the pipe, it may burst.

So, to break the hydrostatic pressure, a tank is specially built which is known as a break pressure tank. In this tank, water is permitted to discharge freely in the atmosphere which reduces the hydrostatic pressure to zero. Storage tank, sedimentation tank, collection chamber, distribution chamber, etc will act as a break pressure tank. Break pressure tank are also called break pressure chamber.

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How to remove efflorescence

How to remove efflorescence ->  For the eradication(complete removal)  of efflorescence problem the source of ingress of moisture should be determined first, the cause of ingress may be due to defective DPC or absence of DPC or other causes.

causes of efflorescence- How to remove efflorescence

How to remove efflorescence

  1. The first action is to stop the source of ingress of moisture.
  2. The second step should be to remove plaster from both inside and outside and leave it to dry.
  3. Then removing the defective bad brick or filling voids with mortar then by cement slurry or cement concrete.
  4. Check the mortar joint carefully and removing loose mortar where necessary.
  5. Wash the white patches surface with the acidic water and then wash it again with clean water.
  6. Plaster both inside and outer surface with cement mortar adding waterproofing admixture.
  7. If causes are due to the absence of DPC course or due to failure of DPC; new course of DPC should have to be introduced or replace the defective DPC by the new one.

It can also be done by following;

a. Brushing

Brushing soluble salts deposited can be removed with a stiff bristle broom. Note that all brushed of materials should be totally removed by a vacuum cleaner or other means. If the result is not satisfying, scrub with clean water then lightly rinse the surface. Note that adding water may result in further deposits, repeated dry brushing as the deposit appears is probably the best treatment. Insoluble salt deposits cannot be removed by water washing although the use of high-pressure water jet is effective.

b. Using a dilute acid solution

The application of a dil. acid solution is also very effective in most cases and in some cases may be the only way. extreme care is required while handling acids. when diluting HCL acid, always add the acid to the water never the reverse.

Ensure good ventilation and also avoid the contact between the acid and the reinforcement. The concrete surface should be cleaned with only diluted acid.

The recommended proportions are 1 part HCL and 20 parts of water. The surface should be saturated always before the application of dilute acid. when applying the acid solution ensure that the surface is surface moist but without any free water is present. Then the applied solution should be allowed to react on the concrete surface for 10-15 minutes. The surface should be thoroughly rinsed and scrubbed with lots of clean water. Repeat rinsing at least twice or until an all traces of the acid solution have been removed. The process may be repeated if required to bring necessary surface finishing.

For water treatment processes- Click here

Water Treatment

Introduction

Water from any source may contain various suspended, colloidal and dissolved impurities which may be harmful or useful for drinking purpose. The removal of undesirable matters and pathogens from water is called water treatment. The degree of treatment depends upon the quality of water desired or required.

Various components are established in treatment plant with well-equipped lab for the test as per treatment required.

These are  various impurities having sizes as :

  1. Suspended Impurities      –   size larger than 10⁻³ mm
  2. Colloidal Impurities           –    size between 10⁻³ mm to 10⁻⁶ mm
  3. Dissolved Impurities         –    size smaller than 10⁻⁶ mm

Objectives of the water treatment process

  • To reduce the impurities to a certain level that does not touch harm to human health.
  • To reduce the objectionable colour, odour, turbidity and hardness.
  • To make water safe for drinking.
  • To eliminate the corrosive nature of water affecting the pipe.
  • To make it suitable for a wide variety of industrial purpose such as steam generation, drying, etc.

Methods of the water treatment process

The water treatment process includes many operations like screening, aeration and sedimentation, sedimentation with coagulation, softening, filtration, disinfection, etc. The water treatment process generally adopted depends upon the quality of raw water and quality of water derived.

1. Screening

When water derived from the surface contain large suspended as well as floating matters which may be sticks, branches, leaves, etc; the screens are fixed in the intake works or at the entrance of the treatment plant to remove the suspended as well as floating matters like branches, leaves and sticks.

water treatment

1.1 Purpose of screening

  • To remove large suspended as well as floating matter such as leaves, branches, dead animals, etc.
  • To work as a protective device for a successive treatment.
  • To increase the efficiency of the successive.

1.2 Types of Screen

a. Bar Screen

Bar screen is also called coarse screen. They have wider opening and are placed in front of the fine screen to remove large, floating and suspended materials.

b. Fine Screen

Fine screen is used to remove smaller, floating and suspending matter of size smaller than removed by the coarse screen.

2. Sedimentation

The process of the removal of suspended particles by gravitational settling is called sedimentation. The water after screening may contain various suspended impurities like silt and clay particles.

The particles whose specific gravity is greater than that of water gets settles down under the action of gravity.

Sedimentation tanks are designed to reduce the velocity of flow of water so that the suspended particles get settled under the action of gravity. Sedimentation can be achieved in two ways.

water treatment

1. Plain Sedimentation 

When the suspended particles are separated under the action of gravity only, it is called plain sedimentation.

2. Sedimentation with coagalities

Fine suspended particles and colloidal impurities are not removed by plain sedimentation. Particles of sizes 0.006 mm required 10 hours to settled in plain sedimentation.

Therefore we need certain chemicals to add in the water to remove such impurities which are not removed by plain sedimentation. These chemical are known as coagulants and the process is called sedimentation with coagulation.

Examples of coagulants are (Al₂SO₄) ₃, AlSO₄, odium aluminate, etc.

3. Aeration

It is the process of bringing water to contact to atmospheric air that contains oxygen. Aeration is one of the important operations for gas transfer in water.

water treatment

3.1 Purpose of Aeration

  • To remove taste and odour by gases due to organic decomposition.
  • To increase the dissolved oxygen.
  • To remove hydrogen sulphide that causes odour.
  • To decrease carbon dioxide in water.
  • To kill the bacteria to some extent.

3.2 Methods of Aeration

Aeration is done by following the main types of Aerators:

  1. Freefall aerators
    i. Cascade aerators
    ii. Inclined aerators
    iii. Flat tray aerators
    iv. Gravel bed aerators
  2. Spray aerators
  3. Air diffuser aerators

4.Filtration

Sedimentation and sedimentation with coagulation removes a large portion of suspended as well as colloidal particles those have specific gravity more than water. There are some particles that have a specific gravity less than or eq1ual to water which cannot be settled by the process of sedimentation.

For removing such particles and bacterias, odour and taste; another operation is needed. The process of passing water through beds of sands or gravels is known as filtration. It consists of a bed of sand supported on gravel.

filtration

4.1 Types of Filter

 

  1. Slow Sand Filter
    These are the initial type of filter introduced in 1829 in England. The rate of filtration through a slow sand filter is very slow. The rate of filtration is 100 to 200 litre per sq. m per hour.
  2. Rapid Sand Filter
    The rapid sand filter is mostly used for treatment works in municipalities. The rate of filtration work is 3000 to 6000-litre per square meter per hour.
  3. Pressure Filter
    In this filter, water passes through the sand bed under pressure. This filter is used for industrial plants.

5. Disinfection

A slow sand filter can remove up to 99% pathogens. However, this percentage is less in the rapid sand filter. So in order to neutralize the effects of remaining organisms; the water is passed through the disinfection process.

The killing of harmful bacteria with the help of chemicals or substances is called disinfection and chemical used are called disinfectant. Examples of disinfectant are hydrogen peroxide, formaldehyde, sodium hypochlorite phenol, etc.

(Note: Sterilization is the process of elimination of organisms either they are useful or harmful.)

water treatment

5.1 Purpose of disinfection

  • To kill pathogenic bacteria and organisms present in water.
  • To make people safe from water-borne diseases.
  • To reduce the chance of epidemics.

5.2 Requirement of a good disinfectant

  • The disinfection should be able to remove all pathogenic in a short time.
  • It should be cheap and easily available.
  • The water should not be toxic and objectionable after addition of disinfectant.

5.3 Methods of disinfection

5.3.1. Physical Method

  1. Boiling
    Boiling of water is an effective and safe practice for disinfection of pathogenic micro-organisms. It is not feasible for community water supply due to the high energy requirement for boiling water.
  2. Sun Light
    Pathogenic organisms can be destroyed by solar radiation. It has been found that if the water in a transparent bottle is exposed to full sunlight for about 7 hours, the water is completely disinfected.

5.3.2. Chemical Methods

Some of the chemical tests in the process of disinfection are:

  1. Chlorination
  2. Bromine treatment
  3. Iodine treatment
  4. Ozone treatment
  5. Silver treatment
  6. Potassium permanganate treatment

Among them all; chlorination is the most widely used method. SO, we are explaining only chlorination.

Chlorination is the process of addition of chlorine to kill the bacteria. Chlorination is widely adopted in all developing countries for the treatment of water in the public water supply system.

# Layout of the water treatment plant

Following are the major consideration for the layout of a treatment plant:

  • The water treatment plant should be located near the distribution area to reduce the contamination in distribution.
  • All the units are arranged in a way that minimum area is required to reduce the cost of construction.
  • All the units of plants should be located in an order of sequence flow from one unit to another by gravity.
  • There should be the availability of sufficient area for future expansion.
  • For operation and maintenance, staff should be provided with staff quarters near to the treatment plant. So that the operator can watch plants easily.