GROUNDWATER CONTAMINATION: EFFECT OF SANITATION SYSTEMS IN RURAL INDIA

Of late there is lot of awareness among rural population regarding the usage of toilets and related hygienic conditions. Government agencies and NGO’s are participating in a big way in this programme. Government of India initiated a program “Total Sanitation Campaign” (TSC) with the objective of eradicating the practice of Open Defecation by 2012. This programme has become part of Rural water supply schemes for the past 5-10 years. Water supply schemes providing safe drinking water to villages and towns had priority in earlier schemes. But now, water and sanitation schemes are being contemplated simultaneously.

The objective of these schemes is to maintain adequate sanitation and provide safe drinking water to rural population. There appears to be a lot of progress achieved in sanitation and water programmes. In spite of commendable progress achieved in these schemes, surveys have revealed that even after a massive programme of toilets construction, there appears to be little change in the overall health status of public. As per the surveys conducted in Maharashtra, from 1996-97 to 1999-2000, more than 16 lacLatrines were constructed, but still there is very little improvement in the health sector, where the number of water borne diseases do not show any significant reduction in the subsequent years.

Table 1: Status of water borne diseases in Maharashtra

Disease	1999-2000 (Attacks)	2000-2001 (Attacks0	2001-2002 (Attacks)
Gastroenteritis	65,067	32,479	67,295
Diarrhoea	10,23,194	11,46,395	11,04,841
Inf. Hepatitis	16,159	13,343	12,066
Typhoid	13,079	15,438	13,320
Cholera	348	1,043	1,326

Source: Drinking water and sanitation in Rural Maharashtra: A review of policy Initiatives By Shree Keshab Das

Despite spending crores of rupees to contain water pollution, water samples are continuously failing to meet the prescribed quality standards. Same situation and conditions exist in other states.

Probable Reasons for Poor Groundwater Quality

·         The most common water quality problem in rural water supply is bacterial contamination from septic tanks which are often used in rural areas.

·         Pollutants also move into groundwater through

·         macro pores

·         root system

·         animal burrows

·         Abandoned wells.

·         Closer the contaminant source is to the water well, more the chances of pollution.

·         Greater the distance between source of contamination and groundwater abstraction structure, the more likely that natural processes like Oxidation, Biological degradation and Absorption reduce the impacts of contamination.

·         Septic tanks that do not have sewage treatment systems.

·         Arrangements for safe disposal of solid waste, rain water, and domestic liquid are lacking in many villages.

·         Effluent (overflow and leakage) from septic tank can percolate (seep) down to the groundwater.

The risk of contamination is greater in the areas where shallow groundwater conditions exist. The Central Groundwater Board maintains National Network Observation  Well data  Water Level Information gis2.nic.in/cgwb/Gemsdata.aspx). As per this  data, it is observed that in Andhra Pradesh state, as against 693 number of observation wells (generally one observation well represents one mandal having average of around 20 villages in Andhra Pradesh; in other states, Taluks and Blocks are common where more than one observation is established to monitor the seasonal water levels), 113 number of wells recorded 0-2 meter water level below ground level during rainy season. District wise details of shallow groundwater conditions (0-2m bgl) are given below.

Table 2: Shallow Groundwater Conditions

SL.NO	Name of District	No of observation wells taken for analysis	No of wells in the range of 0-2 m water level during rainy season	Probable reasons for near Ground level  water table conditions during rainy season.
1.	Srikakulam	50	9 no obs wells	Groundwater exploitation is low,hilly area more
2.	Vizianagaram	24	10 nos	---Do----
3.	Visakhapatnam	46	3	Half of the area is tribal, other half well developed in irrigation.
4.	East Godavari	74	22	Delta area, along the River Godavari and Canal command area.
5.	West Godavari	62	15	Along the River Godavari with canal net work .
6.	Krishna	67	13	More delta area.
7	Guntur	95	13	Along River Krishna and canal net work.
8.	Prakasam	34	3	Sea coast  and valley fill areas
9.	Nellore	68	5	Sea coast  and valley fill areas
10.	Chittoor	96	1	Valley fill area
11.	Kadapa	77	1	Foot hill zone and  valley fill area
12.	Anantpur	26	2	Valley fill area.
13.	Kurnool	41	5	Eastern portion dotted with hills.valley fill area and foot hill zone.
14	Hyderabad	34	5	Near surface  water bodies.
15.	Rangareddy	95	7	------------do----------------
16.	Medak	24	4	Near surface water bodies and foot hill zone
17.	Mahabubnagar	32	8	----------------do-------------------------
18.	Nalgonda	70	5	----------------do-------------------------
19.	Nizamabad	28	5	----------------do------------------------
20.	Warangal	94	11	Eastern portion hilly.valley fill and foot hill Zones.
21.	Karimnagar	44	7	Soft rock area and hilly terrain in Manthani and Mahadevpur areas.Canal command and Foot hill zones.
22.	Khammam	50	8	Major sedimentary  rock terrain. River Godavari is flowing. Tribal area is more.valley fill , foot hill zones and along major streams.
23.	Adilabad	81	14	Tribal and hilly area more.Along the river,foot hill zone and valley fill areas.

Data based on 2008 and 2009 calendar years.

In the above data, observation wells  where the depth to water level during rainy season is 0-2m, are susceptible to groundwater contamination from septic tanks. During rainy season, there is a possibility of mixing of groundwater, drainage water and effluents from septic latrines. In such conditions, water borne diseases affect the villagers who depend on groundwater for drinking water purpose. Water-borne diseases affect the occasional guests, who visit their native villages after spending long time in cities where safe drinking water is available, and floating population. Contaminated water affects the children, old people and occasional guests more when compared to the others. Probably local residents develop immunity to accept contaminated water.

Similarly, in other states also (source: Groundwater Scenario of India 2009-2010 CGWB year book), 4% to 75% of observation wells recorded 0-2m depth to water level during rainy season. The  highest percentage in Assam and lowest percentage in Delhi. Karnataka state recorded 20% of observation wells, TamilNadu 5% observation wells, Maharashtra 31% of observation wells recorded the depth to water level from zero to 2m below ground level during rainy season. The near ground level water table  record particularly  during rainy season in Delta areas, along the major Rivers, Canal and Tank command areas, Buried pediments, Valley fill areas, Tribal and Forest areas where groundwater exploitation is low to negligible. In absence of underground drainage system, groundwater contamination is possible due to numerous types of human activities such as

1. Residential

2. Municipal

3. Commercial

4. Industrial and

5. Agricultural activities.

Water Related Diseases Due to Microbial Contamination

 Water-borne diseases are Viral, Bacterial, Protozoal and Thread worm.

 Viral diseases are infective hepatitis and polio-myclitis

 Bacterial diseases are diarrhoea, dysentery, cholera and typhoid

 Protozoa diseases are amoebiasis, giardiasis, helminthic i.e round worm and thread worm.

Mathemoglobinemia or blue baby syndrome, an illness affecting infants, can be caused by drinking water that is high in Nitrate.

Microbial drinking water quality test is very important at the Source and Point of abstraction. Household containers also spoil the water quality. Monitoring of drinking water catchment, point of abstraction and container water quality also should be carried out to find out where the contamination of groundwater took place and level of pollution at different places i.e at source, point of abstraction and in water containers.

Bacterial indicators E-coli, Thermotolerant coli presence in drinking water indicates contamination. E-coli is derived mostly from human and animal faeces. Thermotolerant coli grows at 44 degree centigrade. Faecal Streptococci is an indicator of faecal pollution, and survive longer water environment than E-coli.

Remedial measures

1.       If the groundwater contamination is very high, water supply must be abandoned as a source of                                        drinking water.

2.        In other cases, groundwater can be treated and supplied to public.

3.       Prevent the contaminated water to migrate.

4.        Pumping the water, treating it and returning it to the aquifer.

5.        Allowing the contaminant to reduce naturally following the implementation of appropriate source control.

6.       In the villages where safe drinking water is provided under Rural water supply schemes, it is essential that water pipes should not go through sewage or should not be submerged in sewage locations. Since in the villages, sewage channels are open, there is the possibility of sewage mixing with pipe water.

7.       Though it is a monumental task, we wish someday underground drainage system should come to all the rural areas which reduces the contamination of groundwater from organic particles.

8.       In rural areas, at present, Rural water supply schemes are being implemented under Water and Sanitation. The objective of the scheme is to provide safe drinking water providing Tap connections and ensure all the households construct latrines so as to avoid open defacation. But large number of villages still depend on Dugwell or Borewell with handpump for drinking water. Also, open defacation is practiced in many villages and few villages adopt septic latrines. There is big drive in the rural areas to have latrines in each house. This practice also leads to groundwater contamination.

9.       Efforts should be made to reduce the water contamination by adopting better methods of sanitation. Disposal of drainage water, sewage disposal, distance criteria maintained between sanitation and drinking water source and abstraction. Periodic monitoring of microbial groundwater quality and sanitation risk inspection data for water source (Dugwells and Borewells) questionnaire as prescribed by WHO in their water quality reports

Problems confronting in Drilling of Borewells/Tubewells in different Geological formations in India.

It is common practice to observe that only DTH rigs are operating in Hard rock areas, Direct Rotary drilling machines in unconsolidated or alluvial formations and Percussion drilling machines in the areas where boulders, gravel and karst topography(limestone solution cavities) are prevalent. Percussion drilling also can be taken up in consolidated and unconsolidated formations but the drilling rate is slow and financially not viable compared to DTH and Direct rotary drilling methods. But the problem arises when alluvial formations or unconsolidated formations encountered in predominantly dominated Hard rock areas.Similarly,several problems occur when the local boring methods are being used instead of Direct Rotary drilling method   in unconsolidated formations,particularly when the depth of Tubewells increases from 25 feet to more than 100 feet  due to increase in utility of groundwater.

Reference: http://welldrillingschool.com/courses/pdf/DrillingMethods.pdf

Common problems in Hard Rock Areas

(http://cgwb.gov.in/District_Profile/AP_districtProfiles.html)

1.    Problems due to occurrence of unconsolidated formations

The alluvial formations occur in hard areas in patches due to buried river channels, along stream courses, floodplains, palaeo-channels etc or lake beds which are encroached for building construction. As only DTH rigs are available in hard rock areas,(as  Direct Rotary drilling or local hand boring methods are not available )drilling for bore wells in this area taken up by DTH rigs have to be abruptly stopped due to collapse of unconsolidated formations and as such drilling could not be proceed beyond 12 to 15 meters. And the owners of the buildings who have no other option except to satisfy with these shallow bore wells having very limited quantity of water. But later few years, the residents of the building face water scarcity as the shallow bore well goes dry. Direct Rotary drilling rigs or combination Rigs(combination of DTH and  Rotary  drilling) are not available in these areas to take up drilling under such conditions.

     2. Problems due to occurrence of Limestone Karsts topography:

In Singanamala mandal of Anantpur district, drilling of bore well came to an abrupt end at 100 feet as the DTH rig could not proceed further as continuation of granite rock is missing. This area is transition zone for Archaean Granite Gneisses and Kadapa rock formations. In fact Limestone formation having solution cavities (Karst limestone) struck at 100 feet. In Karst topography, Percussion drilling rigs could be able to drill bore wells but such rigs are not available in this area.

    3. Distance criteria not followed in urban areas:

In urban areas like Hyderabad large number of bore wells are drilled for drinking water

purposes. Due to increase in number of Apartments, the prescribed distance criteria between two Bore wells are not being followed. With the result, certain problems cropped up in the performance of Bore wells.  Some of the important problems are -lowering of water table, reduction in discharge of bore wells, and hampering of drilling progress. In the areas where bore wells are located close to each other I:e distance between two bore wells is about 20 meters and less-when drilling is under progress for new bore well, the Air that is emanating from Air Compressor- instead of adding to the  progress of drilling, Air get leaked through adjacent bore well/Dug well and hinder the progress of new bore well. The drilling process has to be stopped at this stage and make a retreat.

4. Effect of thick clay layer on the success of Bore well:

In one of the villages of Srikakulam district, it was observed that a bore well was drilled up to 150 feet which was located in highly favorable location turned out to be a unsuccessful well. Nearby river is flowing by the Bore well location has good catchment area and weathered rock existing up to the depth of 90 feet. The reasons for failure of Bore well could not be traced out easily. After a detailed investigation of the area, it was observed that one meter thickness of Clay is overlying the weathered rock and not allowing surface water to percolate to sub surface. There is one big Lake located in the village having abundant water. It was reported by villagers that throughout year, water exists in full capacity of the lake as underlying clay material will not allow any percolation to subsurface water. There is only evaporation of lake water and no recharge to groundwater. Thick clayey material is common in hard rock areas particularly in Kadapa formations, Deccan trap areas and in Achaeans.

    5. Highly weathered formation: In few locations, highly weathered (loose soil) formations from 80 to 100 feet struck in few bore wells. Generally Rig operators lower casing pipe up to 25 to 40 feet and complete the construction of bore well. In such cases, after few days of pumping it will be noticed that discharge of bore well has decreased. The reason for reduction of discharge is collapse of bore well from 40 feet onwards till the hard rock strikes. Casing pipe should cover the entire thickness of highly weathered rock formation.

Problems confronted in unconsolidated formations:

1. About 2 decades back, in Deltaic areas, Coastal areas, along stream courses and sometimes in command areas of Water bodies, filter points and shallow Tube wells depth up to 25 to 35 feet used to be ground water abstraction structures. Of late dependence on groundwater has increased in these areas, consequently, the depth of filter points and shallow tube wells in these areas has increased to 100 feet and some places the depth is more. But in these areas, though the depth of shallow tube wells increased, the same old methods of hand boring methods are still being practiced. It is a simple way of constructing shallow tube wells in alluvial formations without lowering slotted pipes or gravel  filling as  per the subsurface geological conditions. For shallow depths, these hand boring methods were working satisfactorily due to abundant groundwater. But for the deep tube wells (above 100 feet) certain problems encountered during the operation of these tube wells drilled by local boring methods. Main problems are, low discharge, muddy water and collapse of bore well etc. When number of tube wells are increased and depth of wells increased, it is necessary to follow proven technical methods while taking up the construction of wells. But the cost of construction of Tube wells on proven technical methods is high and the Direct rotary drilling methods with mud circulation are so far employed by government agencies only. The drilling process includes delineation of subsurface litho logical data, selection of gravel packing material as per geological formations, selection of slotted pipe, blank pipe, and development of Tube well until the water become free from clay, silt and Sand. In few locations, farmers constructed the tube wells lowering the casing up to the bottom of tube well without using slotted pipe and gravel packing etc. In such cases wherever sand zones are struck, the drilling will be stopped and lower the casing up to bottom. In such cases full potential of groundwater sources could not be exploited due to inadequate application of required technical methods.

2. Inadequate knowledge while encountering saline water. The quality of groundwater problem occurs along the coastal belt and in deltaic areas. The salinity problem is very complex and there is no uniformity in the pattern of occurrence of saline water. In the coastal areas of Andhra Pradesh and Tamilnadu states generally, fresh water occurs on upper shallow zone and saline Water encounter below the fresh water. In cities like Chennai and small towns located along the coastal area, utmost care is to be taken to pump out fresh water overlying the saline water. Any overexploitation or overdraft in this area will yield saline water particularly during summer season. The situation is so delicate in Chennai city, in the western portion of the city fresh water occurs up to 70 feet below ground level and  towards east(towards Sea)in intermittent zone, fresh water is available up to 50 feet and near coast fresh water is available up to 20 to 25 feet only.  More new number of wells and more exploitation of water lead to discharge of saline water.  Thanks to the efforts of state government which made Rain water Harvesting structures compulsory in all the Apartments of Chennai city which makes the situation better, as far as the availability of fresh water is concerned.

  In rural areas of coastal area, agricultural activities and fish pond culture has increased the exploitation of fresh water which caused yielding of saline water in few locations. This has resulted severe drinking water problem along the coastal area. In such areas, local authorities supplying drinking water through tankers.

  In deltaic areas of Godavari, Krishna and Cauvery rivers, shallow tube wells are generally drilled up to 70 to 100 feet which gives high yield of potable groundwater.  In addition, along River courses, along canals, potable groundwater is available in shallow tube wells.

The situation is quite different in west Bengal where in few major stretches like Diamond Harbour-Namkhana track , Saline water occur on upper zones and fresh water in lower zones. The same situation continues up to major part of Orissa state but near Puri Town,  the position changes where fresh water occur on upper zone and saline water underlying it. In coastal Gujarat both the conditions exists, i.e some places saline water occurs on upper zones and in lower zones fresh water and in other areas, reverse positon is existing.

In the areas where groundwater quality problem exists, the drilling units should be capable of carrying out Packer tests and cement sealing tests so as to seal the saline water and tap only fresh ground water. These techniques are so far used by government agencies and ordinary farmers should be able to follow these techniques. Government agencies or NGOs involved in such activities should guide the farmers when they go for Tube wells in their areas.

The problems which encounter in hard rock areas due to occurrence of unconsolidated formations, thick clayey layers and construction of Tube wells by local boring methods are prevalent in large part of Southern India and Deccan trap areas of Maharashtra, parts of M.P and Gujarat. In remaining parts of the country also similar problems occur though extent of hard rock areas is limited. There should be some agencies which should take care of such problems by taking extra efforts as the cases reported are few in number from Taluka and district level. Or some system should be evolved to register the cases from different areas and chalk out a plan to tackle the situation.

C Satyanarayana

Retd.Dy.Chief(Hydrogeology)

REC.

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