Q Bank for Civil Engineer LDCE Exam- Write Short Notes on (21)

Q.No.15. Write short notes on the following

i) Quality of drinking water

Ans:- Quality of Water - It should be ensured that the water supplied for domestic and public consumption is clear, potable, and free from pathogenic organisms, undesirable taste and odour. Water should be of reasonable temperature and free from minerals which could produce undesirable physiological effects. The physical, chemical and bacteriological standards should be as per IS 10500. ii) Chlorination of water:-

Chlorination Methods : Generally following three methods are adopted for chlorination of water using different chlorine producing agents. 

 (a) Bleaching powder solution is added to the water, the chlorine available in bleaching power is used to disinfect the water. This method is suitable only for smaller requirement of water. 

 (b) Chlorine is produced by electrolysing a solution of brine or common salt and the chlorine so produced is used for disinfection. 

 (c) Chlorine is obtained directly from the cylinders filled with pure chlorine in gaseous or liquid form. This method is generally adopted for larger size of water supply plants The residual free chlorine available one-hour after chlorination should be 0.5 mg/L.Chloroscopes to know residual chlorine and Horrocks apparatus to assess chlorine demand of water should be available with all Engineering staff in-charge of chlorination and all Health Inspectors. .

5.3 Chlorine demand When chlorine and chlorine compounds are added to a water source, it purifies the water by damaging the cell structure of bacterial pollutants, thereby destroying them. The amount of chlorine needed to do this is called the chlorine demand of the water. The chlorine demand varies with the amount of impurities in the water and therefore the chlorine demand of a water source will vary as the quality of the water varies. Chlorine and chlorine compounds are consumed by inorganic and organic matters present in water before any disinfection is achieved. For achieving proper disinfection of water by killing the pathogenic organisms, it is essential to provide sufficient time and dose of chlorine to satisfy various chemical reactions and leave adequate amount of chlorine as residual in the form of free or combined chlorine. The difference between the amount of chlorine added to water and amount of residual chlorine after a specified contact time is the chlorine demand. In other words it is the amount Cl2 that is needed to destroy bacteria and to oxidise all organic matter and ammoniacal substances present in the water. Chlorination Practices :

There are generally two practices as explained below :- 

 (i) Plain chlorination : This is applied where water is relatively less polluted and sufficient contact period of at least 30 minutes between the point of chlorination and consumer point is available. 

 (ii) Super chlorination : This is adopted in case of water being heavily polluted or where available contact period is short i.e. less than 30 minutes. In case of super chlorination, it may be necessary to go in for dechlorination to remove the excess residual chlorine.

Residual Chlorine:

Residual Chlorine is a low level of chlorine remaining in water after its initial application. This is an indicator that Chlorine Demand is satisfied. It constitutes an important safeguard against the risk of subsequent microbial contamination after treatment The provision of IRWM 2000 are as under: 

The Health Inspectors should check the presence of residual chlorine daily at various distribution points e.g. platforms, refreshment rooms, waiting halls, hospitals, schools and in the Railway colonies (preferably from farthest taps in the distribution systems), randomly and record of the same should be kept in a register. Suitable remedial measures should be taken in case of deficiency. Health Inspectors should also test the bleaching powder used once in 3-4 months for Chlorine content (must contain at least 25% of chlorine). The residual free chlorine available one-hour after chlorination should be 0.5 mg/L (Which is 0.5 PPM).

Detection of residual chlorine : Detection of residual chlorine can be done by a simple apparatus known as chloroscope using orthotolidine test (OT) and orthotolidine arsenite test (OTA). The OT is used to determine the total residual chlorine concentration and the OTA is used to determine the free and combined residual chlorine separately. When orthotolidine reagent is added to water sample containing chlorine, a greenish yellow colour develops, the intensity of which is proportional to the amount of residual chlorine available in the water sample.

The OT test is not as accurate as the presence of nitrates; iron and manganese also produce a yellow colour with orthotolidine. The test using OTA is more reliable. 

iii) Inspection of LWR Ans:- While requiring less maintenance, LWR/CWR necessitate intensive inspection at supervisory and officer’s level.The profile of the ballast section shall always be checked, especially at pedestrian/cattle crossings, curves, Approaches of level crossings, points and crossings and bridges. Cess level should be correctly maintained. Replenishment of ballast shall be completed before the Onset of summer. Inspection shall be more frequent in the afternoons during summer months. During inspections, look out shall be kept for kinks, incipient buckles and checks made on functioning of the patrols. Knowledge of staff in regard to prescribed maintenance practices shall be periodically checked and it shall be ensured that the work is done accordingly.Ultrasonic examination of rails should not be in arrears. Defective rails/welds should be replaced expeditiously. Inspections of gaps at SEJ and creep/movement at centre of LWR/CWR by Permanent Way officials would be done as per following schedule:- 

i) PWI-Incharge/PWI Sub-section:- 

a) Every fortnight during the two coldest and two hottest months of the year at about minimum and maximum temperatures alternately by PWI Incharge and PWI Sub-section. 

b) Alternately once in two months during other months of the year. 

ii) Assistant Engineer:- At least once in six months, preferably during coldest and hottest months.

RECORDS

Record of LWR/CWR, as per the proforma laid down in LWR MANUAL shall be maintained by the PWI in a permanent register called the Sectional LWR/CWR Register. The PWI shall be responsible for keeping this register up-to-date.It should also be maintained in TMS. An indication plate similar to that suggested in para 212(4) of Indian Railways Permanent Way Manual shall be fixed on the cess at each SEJ showing the date of destressing, destressing temperature td/ to and length of LWR/CWR.

(iv) HOT WEATHER PATROLLING:- 

ANS:- Period for hot weather patrolling shall be laid down by the Chief Engineer for each section and patrol charts prepared where necessary. Patrolling shall be organised by PWI accordingly. In addition, the PWI/PWM and the Gangmate shall be vigilant during summer and on hot days. Hot weather patrolling will also be introduced, when the rail temperature rises above td+25 degree Centigrade 1. Hot weather patrolling will be carried out as follows:- 

i) On single line or where only one road in a double line section is having LWR/CWR - One patrolman for 2 km. 

ii) On double line section when LWR/CWR exist on both roads - One patrolman for 1 km length of UP and DN road. The beats of each hot weather patrolman will thus be restricted to 2 km. 

2. The hot weather patrolman should always carry the following equipments:- HS Flags - Red 2 Staff for Flags 1 Detonators 10 Canne-a-boule 1

3. Duties of hot weather patrolman are as follows:- 

He will walk over his beat slowly over one rail in one direction and on the other rail in the return direction. On double lines, he will repeat this procedure alternately on UP and DN tracks. He will be vigilant and look out for kinks in the rail especially during the hottest part of the days. When a kink is observed, he shall immediately examine at least 100 sleepers ahead and in the rear of the kink for any floating condition of track. He should meticulously sound each and every sleeper, 100 sleepers on either side of the kink, to determine any floating condition. The sounding will be done by dropping a canne-a-boule on each end of the sleeper to determine the extent of void under the sleeper. Should the sounding reveal a floating condition, under which a buckle may be anticipated or the patrolman has detected actual buckling of track, he will take immediate steps to protect the affected portion by display of hand signals as per rules in force. After protecting the track, the patrolman will arrange to advise the Gangmate, PWM, PWI of his apprehension of a buckle/actual