After reading this article you will learn about:- 1. Standards for Drinking Water 2. Water Quality Requirement 3. Sampling.
Standards for Drinking Water:
The U.S. Public Health Service has laid down the following standards for drinking water:
ADVERTISEMENTS:
(a) Physical characteristics:
The drinking water should be free from such impurities which would cause offensive taste, smell and sense of sight. Following physical limits should not be exceeded otherwise water will become unfit for drinking.
(b) Chemical characteristics:
The concentration of metals and other chemical substances in potable water should not be exceeded by the amount given in the following table.
(c) Bacteriological Standards:
ADVERTISEMENTS:
(i) Water entering the distribution system:
Coliform count in any sample of 100 ml should be zero. A sample of the water entering the distribution system that does not conform to this standard calls for an immediate investigation into both the efficiency of the purification process and the method of sampling.
(ii) Water in the distribution:
ADVERTISEMENTS:
Water in distribution system shall satisfy all the three criteria indicated below:
(A) E-coli count in 100 ml sample should be zero.
(B) Coliform organisms not more than 10 per 100 ml shall be present in any sample.
(C) Coliform organisms should not be detectable in 100 ml of any two consecutive samples or more than 50% of the samples collected for the year.
ADVERTISEMENTS:
The appearance of higher numbers in any sample should necessitate the investigation and removal of the source of pollution.
(iii) Individual or small community supplies:
E-coli-count should be zero in sample of 100 ml and coliform organisms should not be more than 3 per 100 ml.
(d) Virological standard:
0.5 mg/1 of free chlorine residual for one hour is considered sufficient to inactivate virus, even in water that was originally polluted.
This free chlorine residual is to be insisted in all disinfected supplies in areas suspected of endemicity of infections hepatitis to take care of the safety of the supply from virus point of view which incidentally takes care of the safety from the bacteriological point of view as well. For other areas 0.2 mg/1 of free chlorine residual for half an hour should be insisted.
Water Quality Requirement:
2.1. Inland Surface Waters for use as Raw Water for Public Water Supply and for Bathing GHATS — Inland surface waters for these uses shall satisfy the tolerance limits prescribed in Table 3 when tested according to the methods indicated in col 4, 5, 6 and 7 of the table.
Note:
1. For requirement for mercury, see 0-6 ISI booklet.
2. ‘Methods of sampling and test for microbiological examination of water used in industry. Methods of sampling and test (physical and chemical) for water used in industry,
3. Methods of sampling and test for industrial effluents. Part I.
4. Methods of sampling and test for industrial effluents. Part III.
In the inland surface waters for bathing GHATS, no visible floating matter of sewage or industrial waste origin, and no unpleasant odour shall be present
Inland Surface Waters for Fish Culture:
Inland surface waters for fish culture shall satisfy the tolerance limits given in Table 4 when tested according to methods indicated in col 4, 5 and 6 of the table.
Test for Freedom from Toxic Substances:
When tested for 96 hours as prescribed in IS: 6582-1971, not more than 10 percent of test animals shall die and not less than 90 percent of test animals shall be found in apparently healthy state.
Table 4:
Tolerance limits for inland surface waters for fish culture (Clauses 2.2 and 4.1)
Note:
For requirement for suspended solids, sec 0.7.
Methods of sampling and test (Physical and chemical) for water used in industry
Methods of sampling and test for industrial effluents, Part I
Inland Surface Waters for Irrigation:
Inland surface waters for irrigation shall satisfy the tolerance limits prescribed in Table 5 when tested according to the methods indicated in col 4 and 5 of the table.
3. Sampling:
For Coliform Test:
Representative samples for coliform test shall be drawn as prescribed in IS: 1622-1964.
Note:
In agricultural practice, it is usual to express concentration of ions in terms of milli-equivalents per litre (meq/1) instead of milligrams per litre.
The following conversion factors shall be used to convert values from one system to the other:
For Other Tests:
Representative samples for the other tests given in this standard shall be drawn as prescribed in 2 of IS: 3025-1964 at a point from where the water is to be taken for the purpose in view.
Tests:
Tests shall be carried out as prescribed in IS: 1622-19641, IS: 3025- 1964, IS: 2488 (Part I)-1966$, IS: 2488 (Part II)-1968 §, 
The growth responses have established that the test alga are much sensitive to bio-reactive state of hexavalent chromium. The < 95 percent I14 algistatic response of algal species in the control test water is similar to that indigenous sensitive species to recent discharges of heavy metals.
There is a gradual loss in biomass of U. fimbriata as the concentration of chromium increases up to 0.15 ppm and further increase causes failure in growth while there is observed a dramatic enhancement in biomass of C. glomerata and S. tenue up to the same concentration and further addition of heavy metal results in subsequent loss at higher concentrations.
a. Subject to relaxation or tightening by local authority.
b. Relaxable to 750 by the local authority.
c. These requirements shall apply only when after treatment, the sewage is disposed of on land for irrigation.
d. These requirement shall apply only when after treatment, the sewage is disposed of on land for irrigation.
Limits for pesticides in wastewater (to be discharged into surface waters) and in drinking water:
The ISI Standards for discharge of industrial effluents are given in Tables 7 and 8. It can be seen from Table 8 that insecticides should be absent in a wastewater discharged into inland surface waters.
However, Ettinger et al. (19) have suggested some values for maximum reasonable stream allowances for a number of pesticides where maximum value has been indicated for methoxychlor (20 ppb) and minimum for endrin (0.1 ppb).
The ISI Standards for wastewaters to be discharged into marine coastal areas are, however, more liberal than that for the inland surface water. The organophosphorus and chlorinated hydrocarbons limits are 1000 µ/l, and 20 µg/l, respectively.
The ISI Standards do not have any limit for pesticides in water and wastewater used for irrigation. There is no toxic effect of pesticides on crops irrigated with pesticide containing water. Moreover, pesticide content in irrigation waters is variable depending upon land and crop management particles. In view of this, no limits could be set up for pesticide in irrigation water and wastewater.
The recommended limits for pesticides in drinking water are given in Table 9. It can be seen that the limit for chlorinated hydrocarbons except methoxychlor is very low, for chlorophenoxy herbicides is medium and for carbamate and organophosphorus is highest. Even then, organophosphorus and carbamate should not exceed 100µg/l.
Guidance for industries for ambient and emission standards:
For the guidance of industries, it is essential to differentiate between ambient air quality standards and emission standards. The ambient standards are goals set on the basis of the criteria reports and are noted as concentrations not to be exceeded more than a specified number of times in a certain time period. Emission standards are amounts which may not be exceeded by any emission source.
California and federal standards for ambient air quality are noted in table 1. These federal standards were set after passage of the 1970 amendments and in response to requirements of that law. The new source performance standards of U.S.A. 1971 are giver in Table 2.
What still remains to be done after the goals for ambient air quality are set? Table 3 summarizes this situation. The ambient standards are set by federal action and it is the states which must implement plans to meet these standards. We have described in order to meet the federal ambient standards (at least in regions with major sources of pollution), states must set up emission standards.
These standards define who can emit what and possibly even when the emissions will be allowed. In order to set emission standards and of particular interest to engineers, is the need for a diffusion model, including chemical reactions, for the air quality control region. Such a model must be able to take known sources of pollution and to determine the ambient levels of each pollutant.
Meteorology, topography and chemical reaction kinetics must be incorporated into the model. The ultimate simulation will require information about the winds, the solar radiation input the temperature as a function of altitude, and the different moving and stationary sources of pollution.
This will be combined with the equations which govern motion through the atmosphere and the equations for chemical reactions and kinetics. The model will provide an output of pollution concentrations as a function of position and time. No one has yet formulated a complete model but more and more complete computer programs are being developed.
