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ONSHORE ENVIRONMENTAL DRILLING

   
V.R.A. Kidwai, Executive Engineer, Central Ground Water Board, Div.IV, Chennai-90 –Environmental drilling involves the specialized applications of geotechnical and water well methods to monitor the quality of ground water and assist in the control and remediation of ground water pollution.  Specially environmental drilling and sampling methods are carried out in a number of areas such as.

Monitoring and testing for sites such as landfills or lagoons that have a potential for pollution.

V.R.A. Kidwai, Executive Engineer,
Monitoring and testing of environmentally sensitive sites such as protected lands or public water supply well fields.

Sampling and wells construction for recovery of remediation of polluted water and identification of product (oil, petro, etc) or human artifacts (fill, trash, archaeological)
 

Introduction:

Once upon a time, the river water, sea water, pond water and lake water did not pollute due to non availability of chemical industries and fertilizer factories. But now a days mankind needs sophisticated life. As such chemical industries are coming up and most of the pollutions are created by power plant, textile tanneries and automobile industries in which lot of cars are manufactured without notice and awareness of pollution. In cars, lorry etc lot of unburned gases (soot) due to incomplete burning of fuel in Engine. In order to avoid unburned gases, one heating coil system which recently invented by the Engineering students of Anna University, Chennai is being utilized in Auto industries.
 tubewell
 
This coil can be assembled in front of silencer due to which the unburned gases completely burn out and nothing harm to human breathing system.

Since the lot of chemical industries coming up, the chemical and contamination water is being polluted.  Most probably surface water, river and reservoir are being affected that have to be identified by remote sensing, electrical logging and geological  sounding test.  In Tamil Nadu, the river water, surface water completely polluted due to which the human livelihood are disturbed.  On the other hand the air is being polluted by power plants and automobile, which are giving CO2.  In this situation, immediately remedial measures are needed in order to improve situation.  In this juncture, CGWB’s roll is very important to give pure water to people.

RO Membrane system can be utilized in chemical industries for recycling chemical sewerage water for re use so that consumption of water will be minimized. 
 
Aquifer can be located by geophysical methods by taking advantage of the contrast in geophysical properties between water bearings and non water bearing formation. In many surface methods, observations are made to obtain information on the variation of the physical field along a horizontal profile (profiling) or in the vertical section at a given location (ground). The variation in the physical field from the normal field (anomaly) is interpreted in terms of sub surface in homogeneities, which may include variation in lithology quantity and quality of water. In selecting the geophysical method, picking up the critical and distinctive physical method for evaluation is of prime importance. Geophysical surveys may be carried out from the Air, the surface or by lowering instruments in bore holes.
 
On one hand the acute water shortage in the world, on the other side water is being polluted and contaminated by chemical industries, textile industries, etc.   Previously small scale industrial who do not adopt RO systems spoiling the rivers, bore wells etc.   Now a days RO system have been introduced and being adopted widely in Chemical industries.   The affected area has to be find out by Remote sensing Geophysical/sounding test or electrical logging method.   We have to estimate how much has been depth spoiled by chemical pollution by this method.  Accordingly, cement ceiling can be done in between zones in tube well and long cement ceiling in between annular area has to be done in order to avoid chemical pollution.
 

Again electrical logging is required to ascertain or confirm whether chemical pollution completely controlled or not.  After completion of careful investigation the well may be declared for potable drinking water.

Due to contaminated water and chemical polluted water, the river bond, adjoined dug wells and filter point of the irrigation have been affected.  First of all affected areas have to be identified by survey.  It has to be found out how much area and depth have been affected, accordingly rehabilitation measure can be initiated.

The following wells may be constructed in the pollution affected areas in order to overcomechemical/sewage pollution.  Most probably, the chemical pollution has been occurred in loose formation where soils are not compact whereas hard rock formation, it will not enter.   Only we have to rehabilitate tube wells by cement ceiling wherever is needed.

As far as bore wells are concerned over burden long casing is needed to arrest chemical pollution, if required cement ceiling can be done in annular area so that the leakage will not be there in future.   After construction this bore well/tube well should be developed until pure water comes. 
 
Before construction of bore well/tube wells, the chemical polluted area can be measured in the adjoined river/reservoir so as to ascertain the actual requirement of overburden drilling to casing.  Accordingly, we can construct the bore in order to arrest chemical/sewage pollution.

Geotechnical

Geotechnical drilling is carried out to determine soil and in some cases gathered information about the nature of position of the water table from particular sites.   Drilling is conducted to assess potential constructions sites and to confirm conditions.   In addition, geotechnical work can overlap with environmental drilling on sites where there is a potential for environmental hazards. Geophysical survey may be conducted from Air/satellite surface or by lowering instruments in the bore wells.  The main objectives of the geophysical survey are to provide the following information. 

   
arrow Depth thickness of weathered or fractured zones and depth to massive basement rocks, delineation of solution cavities in hard rock
   
arrow Depth of water table
   
arrow Structural and stat graphic condition controlling ground water occurrence
   
arrow Distribution of configuration of salt water/fresh water interface salt water encroachment, pollution and contamination 
 
The occurrence and widespread migration of chemical in the underground environment may ultimately become the most serious threat to ground water quality.  The presence of even tiny amounts of widely used volatile organic chemicals.  Such as trichloroethylene is extremely serious unfortunately many of these substances are not absorbed in the soil particles and thus can travel great distances in the surface environment.
 
Heat pump technology taps geo-thermal vents:  

Making ground source heat a cost effective alternative to fossil fuels has long been a dream for many countries.  A newly developed heat pump technology has made this dream a reality in Slovenia and Serbia. 

 
Fern show how to remove arsenic in Soil:
 
Isolating a gene that allow a type of fern to tolerate high level of arsenic Purdue university researchers hope to use the funding to create plaints than can clean up soils and waters contaminants by the toxic metal. 
 
Definition of Environmental Drilling
 

The drilling which is needed in Chemical sewage polluted area where construction of tube well/bore well is needed according to the environmental condition.

Environmental Drilling classified as follows:
Construction of Model Tube well (Alluvium) in chemical polluted area
Construction of Model Bore Well in Chemical polluted area (Hard Rock terrain).

By logging of pilot hole in Alluvium area, we can identify how long the chemical pollution have been occurred and effected in pilot hole drilling.   Accordingly, the assembly recommendation will be given.   Suppose, the bottom zone lightly affected by chemical pollution and top of the well heavily affected by chemical pollution.   So it should be separated by cement ceiling after gravel shrouding.  Apart from cement ceiling thick clay can be shrouded upto ground level in between annular area.  The thick clay acting as like as wall in which chemical waste water will not enter.   Bottom of the well can be diluted by injection of pure water after development well process completed.   Pure water injection method is not only increase water level but also reduce chemical pollution by dilution of pure water.

After construction of tube well, big gravel can be shrouded in annular area of tube well upto ½ meter depth so that rain wter can be taped in order to dilute chemical elements in tube well.   In horizontal direction, the chemical pollution will not after the well due to clay ceiling.  At the same time, it will be purified in vertical direction by rain water collection through gravel cap.  After some years, the whole well will be cleaned by diluting pure water (i.e. rain water).

Due to soil conservation and changing the chemical pollution can be arrested.  For example in Coastal area Mumbai, one phenomenon has taken place during recent cyclonic effect, the salt water becomes pure under water due to soil change in coastal belt.

On one hand the recent Tsunami has destructed environmental condition on the other hand some advantages has taken place Coastal area waste has completely cleaned.

In the adjoining place, the soil has been changed due to which the direction of hydrology also changed resulting in water levels are increased.

 
Rainfall impacts of climate warming to persist
 

Impacts of manmade green-house warming on rainfall would endure long after temperatures fell, a study suggests.

The U.K. met of his scientists constructed a hypothetical future in which carbon-di-oxide levels rise and then fall, and modeled what might happen to rainfall.

Their computer stimulation showed temperature falling decades after CO2’s declined, with changed rainfall going on for several more decades after that.

 
Hypothetical Future:
 

The hypothetical future saw concentrations of carbon-di-oxide in the atmosphere rising to four times pre-industrial levels over 70 years, then returning to the base line over a similar period.

“This is an idealized situation”, said Vicky pope, head of climate advice at the Met office.

“On the other hand, we could reach atmospheric concentrations of green house gasses equivalent to a quadrupling of CO2 by the end of the century.

“So if we allow emissions to increase to the end of the century and then decrease them rapidly, this is the kind of thing you’d expect to see”, she told BBC news.

The computer stimulation also suggested that if green house gas levels remained elevated for an extended period, the rainfall changes would then endure for longer after emissions began to decline.

Stimulation showed temperature falling decades after CO2’s decline.

Canada and Russia would receive more rain and snow.

 
‘Basic physics’
 
Rainfall changes arrives largely through increased temperature in the ocean.
 
Evaporation
 

More water evaporates into the atmosphere. Overall, this means the world would receive more rain-but computer stimulations suggest the impacts would be very unevenly distributed.

High latitude countries such as Canada and Russia would receive more rain and snow, whereas other regions such as the amazon basin, Australia and parts of sub Saharan Africa would receive substantially less.

 
Manmade greenhouse effect
 

As the oceans have huge capacity to store heat, releasing the heat relating to a temporary quadrupling of the manmade greenhouse effect would take many decades.

The Met office computer model is known to project more drying of the amazon than most others.

“Details of exactly where the impacts fall would be different in different models because they don’t agree in details”, said Dr. Pope.

“But the mechanism is the same in all models, because its basic physics. As models improve, we will be able to get more confident on this”.

 
Studying by isotopic methods
 
Isotopic methods are widely used for the study of groundwater contamination.  This study is designed to provide a basic understanding how isotope techniques are involved in the ground water pollution studies.   Isotope techniques in hydrology are largely based on the tracer concept.   The general objective is to directly trace the movement of water molecules in any part of the hydrological cycle and derive information on the transport processes and how such processes are affected by other factors.
 
Introduction
 
Isotopes are atoms of the same element that differ in terms of their mass.   For example, Hydrogen with an atomic No. of ‘1’ has there isotopes- 1H1, 1H2, 1H3 with mass numbers of 1,2 and 3 respectively.   In many case studies carried out in India, isotopic methods have been demonstrated as highly powerful tool in understanding and solving surface water and ground water related pollution and pollutant transport problems.   Isotope hydrogeochemical and biological data can be used for the development of numerical models for further prediction of contaminant transport in the porous media.
 
Application of isotope techniques in conjunction with hydrogeochemical and numerical and numerical modeling techniques can be used to identify the sources, pollutants and the biogeochemical processes related to fate and transport of pollutants in the subsurface.  Isotope techniques mainly employ environmental stable and radioactive isotopes.
 
Artificially produced isotopes are also used as tracers for study of some specific environmental issues.   From pollution view point the naturally available stable isotopes are of importance to know the source and origin of pollutants include 2H, 18O, 13C, 15N, 34S, 37Cl & 4B.   Naturally available radioactive isotopes such as 3H and 14C are used for estimating the residence time of pollutants in the system.   Apart from these artificial isotopes, 82Br, 131I, 60Co, 198Au etc., can also be used to trace the flow path and rate of pollutant movement.
 
 Groundwater Contamination is not only a local or regional problem, but it is a global issue.  There is a growing concern on potable water all around the globe, mainly due to over exploitation of available resources and lack of proper management.   Estimates suggest that nearly 1.5 billion people lack safe drinking water worldwide and that at least 5 million deaths per year can be attributed to water born diseases.
 

Most of the population in the Indian sub-continent relies on groundwater for drinking, agriculture and industrial use.  Rapid growth of population coupled with ever-increasing demand for water has imposed severe stress on available freshwater resources, both in quantity and quality.  Moreover, in recent years, serious pollution problems have been created due to disposal of untreated domestic and industrial wastes, agricultural activities such as use of fertilizers and pesticides etc.

Stable Isotopes & Role of Isotopic Methods in investigating Groundwater Pollution

 
Sulphur – 34 (34S)
 

Sulphur is one of the common pollutants in groundwater.  By means of standard chemical method one can indicate the presence and its concentration in groundwater.  Chemical method says little about the origin of sulphate.  But the measurement of the δ34S and δ18O of sulphate can elucidate the source of sulphate.

Sulphate of different origin in water comprises, dissolved evaporates, which show δ14S values from + 15 to + 35%o (per thousand) and δ18O values between + 9%o to – 15%o.  From dissolution of secondary sulphate, which originate from the oxidation of metallic sulfide, which show lower δ34S and δ18O.  In most of the cases, the concentrations of sulphates from this origin are much less than that from dissolution of gypsum.   The sulphate which,



comes from the leaching of artificial fertilizers, shows a δ34S near zero and δ18O about + 16%o.

In precipitation, especially in the industrial areas, acid rain containing high sulphate show large variations in δ34S values, which sometimes can be linked to the origin of sulphur.  In most of the seawater, δ34S-isotope content is about + 20%.   Some method, such as bacterial reduction of sulphate can change the original isotopic composition of sulphate.   This process reduces the sulphate concentration and significantly enriches the remaining sulphate in heavy isotopes.   Therefore, sulphur – 34-isotope can be used to understand the source and origin of sulphate in contaminated groundwater.  Shivanna et al., (1903, 1998 & 2000) used sulphur isotope successfully along with other environmental isotopes to study the source and origin of arsenic in groundwater of West Bengal, source of groundwater salinity in Mahanadi delta and Bengal basin. 

In Czech Republic, δ34S and δ18O have been used to study the infiltration of ash born pollutants into groundwater.  Ashes produced by power stations contain a lot of harmful ingredients, seep into groundwater and contaminate it.   The ashes contain sulphur compounds from combusted coal, which are oxidized to sulphate and get into water.  Even though, sulphate does not belong to the most dangerous compound, that can be easily monitored, its presence enables us to observe the infiltration of contaminating substances into groundwater.

 
Nitrogen – 15 (15N)
 

In normal groundwater, nitrate concentration is typically below 2.0 mg/L and concentrations significantly above this are generally regarded as anthropogenic source.  In arid and semi-arid regions, however, some occurrence of high nitrate in groundwater has been recorded which are difficult to explain by conventional methods.   Attempts have been made to detect the origin of nitrate pollution of aquifers through the use of the natural abundance of 15N isotope.

Common sources of nitrate in nature are

Direct leaching of fertilizers
Increased oxidation of soil organic nitrogen because of cultivation.
Oxidation of animal wastes.

Measuring nitrogen isotope ratio of nitrate from different sources and soil environments allow comparison of this ratio with the nitrogen isotope ratios of nitrate in ground water. This technique has been showed to be an effective method for identifying sources of nitrate that may be contaminating an aquifer.

The δ15N of nitrate in soils cultivated without fertilizers ranged from +2.0 to +8.0%o.whereas the δ15N of nitrate resulting from decomposition of animal waste material ranged from +10.0 to +22.0%o. The isotope composition of fertilizer is near to 0.0%o, owing to the synthesis of nitrogen from air. In organic fertilizer, the 15N value is in the range of -2.0 to +2.0%o.

A case study of semi rural Manakau area in New Zealand was conducted by Aggarwal, et al., to see if nitrate isotope could the used to detect the sources nitrate contamination. Nitrogen isotope coupled with oxygen isotope measurements demonstrate that the nitrogen is not sourced from fertilizers but from some contribution of septic tank and animal waste.

Charles et al., (1993), studied the nitrate pollution in ground water of Cretaceous Edwards aquifers in Texas, USA, using nitrogen isotopes. The results showed that, nitrate in ground water of Edward’s aquifer and the iron shore formation originates from two different sources. The 15N of ground water nitrate from Grand Cayman Island clearly indicate that animal wastes are the predominant source for the nitrate. The  δ15N of nitrate in ground water from Edward’s aquifer is similar to the δ15N of nitrate in river water recharge. There were no isotopic evidences of nitrate from septic tanks polluting the ground water.

 
Carbon-13(13C)
 

In ground water, at a pH near neutrality, most of the dissolved inorganic carbon is in the form of bicarbonate. Carbon comes from the atmospheric CO2 and form local biogenic CO2 with a possible component from the dissolution of carbonates which are generally of ancient marine origin. From these interactions, and due to the supplementary effect of isotope fractions between various inorganic dissolved species, a old range of δ13C values can be expected, from about +1 to -22%o. In ground water pollution studies, dissolved carbon of suspected organic origin can be traced through a δ13C study and environmental radioactive 14C can be used to characterize old or fossil carbon.

In the town of Viry-Cgatillon, southeast of Paris, cellars were flooded after heavy rains. A possible origin of water from the nearby phreatic aquifer of the river seine was discarded due to piezometric reason, and leakage from a nearly aqueduct feeding Paris from the Brie was proposed with an alternative hypothesis that the water arose from local springs.

Water chemistry, δ18O and 3H measurements were unable to trace the origin of the flood. However, the delta δ13C of the cellar water matched with the value observed in the aqueduct water, whereas the local springs, in a much less calcareous terrain, gave value of δ13C ~-17%o. subsequent inspection of the aqueduct have shown a very important leak polluting the local area.

 
Chlorine-37(37Cl)
 

The usefulness of stable chlorine isotopes in ground water in pollution studies(ground water salinisation), is becoming important. In crystalline environments a variety of isotopic signatures in ground water may be possible. The degree to which primary processes such as the volatilization of chloride during magmatic events, are the induction of the surface water (sea water) during hydrothermal processes, may occur, can significantly affect both the rock and residual fluid chloride isotopic signature. Later intrusion of sea water, evaporated surface water, leading/weathering of rock would act to change or mix these signatures.

The occurrence of chlorine and the δ37Cl signatures in rocks summarized as follows:

In amphiboles, vein fillings and associated oceanic basalt, the δ37Cl values range from +0.74 to +4.04(SMOC). These values of more enriched that Cl isotopic ratio form associated fluid inclusions. For volatile condensates, the δ37Cl value is -4.88%o and in evaporates and oxidation minerals +5.96%o.

Frape, et al.,(1995)., used stable chlorine isotope technique to identify the source of Cl in ground water of Canadian and FennosCanadian shield. Analysis of δ37Cl values of shield ground water show several different sources of chlorine in these environments and variety of common process which may invoke to account for the observed trends. In Canadian Shield ground water have dominantly negative δ37Cl isotopic signature compared to SMOC and FennosCanadian ground water. FennosCanadian ground weather from a wide range of geological and geographical locations, are dominated by positive isotopic signature and a range of values from -0.06 to 1.97%o. Similar to result of major ions and deuterium and oxygen – 18 of individual study site on each shield have distinct δ37Cl signature.

 
Deuterium(2H) and Oxygen-18(18O)
 
Use of environmental stable isotopic composition of natural water and their variation during condensation evaporation and exchange process have revolutionized the science of tracer hydrology. Analysis of deuterium and oxygen -18 in ground water and their interoperation along with geochemical and hydro geological data leads to valuable information such as the source and origin of recharge, pollutants, to the aquifer (s), source of salinity, etc.
 
Boron -11(11B)
 

Boron is biologically an essential element but it is toxic to many plants at high concentrations. Many crops (Citus and Miritace family) are sensitive to high boron levels in irrigation water. High boron levels in drinking water are also toxic to humans, affecting fertility and pregnancy.

WHO guideline value of boron for drinking water is 0.3 mg/L. in addition to concentration determination, boron isotopes have been increasingly used in hydrological studies during the last decade. The wide range in isotopic composition of the boron sources in water resources, both natural and anthropogenic as well as reactivity of boron with aquifer matrix make boron a useful natural isotopic tracer for delineating source of pollutants in ground water system.

Boron is present in aqueous solutions as B(OH) 4- ion, and dissociated boric acid B(OH)3, polyborate ions and borates. The distribution of these species controlled by the pH, salinity and specification concentration. Boron has two stable isotopes; 11B(79.8%) and 10B(20.2%), which occur in natural abundance ratio of approximately 4:1. Variation of the ratio of these two isotopes is expressed as δ11B.

Boron can be used as a tracer in ground water because of its high solubility is aqueous solution, natural abundance, and the lack of effects by evaporation volatilization and oxidation-deductions. Since boron concentrations in ground water are generally low(0.05mg/L and contaminant sources of usually enriched in boron seawater:4.6mg/L, domestic waste water:1mg/L, Fly ash:14mg/L).  The large isotopic variation of the potential sources can be used to trace the origin of the contaminants and to reconstruct the mixing and flow paths. The main end members with distinguishable isotopic signals are:

Seawater intrusion and entrapped marine origin brines with δ11B values of 39% and B/CL ratio 8x10-4.
Non marine brines entrapped in non flushed areas in aquifers and aquitards with δ11B value s of 0%o and B/CL ratio> 8x10-4.
Hydrothermal fluids in hydrolic connections with fresh water aquifers show δ11B values of 0%o and high B/CL ratio (more than seawater values).

Concentration by domestic water and other anthropogenic sources (fertilizers, feticides and landfills) in which anthropogenic boron is derived from Na-borates with δ11B values of 0%o to 10% and high B/CL ratios contaminants by fertilizers originating from calcium- borate with low δ11B values has -13%o and high B/CL ratios.

 Vengosh,et al.,(1998),applied boron isotope techniques to investigate the ground water salinisation mechanism in postal aquifer poster of Israel, Cornea river in north western Italy and Salinus valley California. In addition, the boron isotopic composition of synthetic boron compounds used for detergents and fertilizers where investigated. The results revealed different contaminant sources; underlying saline water of marine origin in saline plumes in the Mediterrainean coastal aquifer of Israel (δ11B =31.7%o to 49.9%o, B/CL ratio 1.5x10-3), mixing of fresh and sea water (25%o B/CL ratio: ~ 7x10-3); in Salinas valley, California, and a hydrothermal contribution in ground water from Ornia river, Italy.

 
Case studies in India
 

Isotope methods have been widely used in ground water pollutions in India. In hydrological investigations, stable isotopes of water namely, 2H & 18O have been used to identify the source, origin and recharge process of ground water. 13C,15N,34S,37CL and 11B are used to understand the source of various chemical pollutants and the existing environmental condition in the subsurface. Environmental tritium has been used for age dating of modern water.14C isotope helps to determine the age of ground water on time: scales ranking from modern to 40,000 a before present. Age dating helps to estimate the chronologies of ground water contamination.

Environmental isotopes have been used to understand the salinisation process in aquifers. Result show that the present day sea water intrusion is responsible for salinity in postal aquifer of West Bengal and Orissa are due to entrapment of old sea water during the Holocene(~ 8000 years) and late Pleistocene(~ 24000 years) periods. Another study carried out in the metropolitan area of Chennai city shows that the source of ground water salinity in this area is due to dissolution of aquifer material as well as entrapped sea water and changes of present day seawater intrusion in remote.

Environmental isotopes techniques have also been applied to study the arsenic and fluoride contamination in ground water of west Bengal and Karnataka. Isotope data includes that the surface water, shallow and deep ground water are free from arsenic and intermediate zone( 20 to 100m) is contaminated with arsenic. The elevated arsenic concentration in ground water of west Bengal is released from the sediment under anoxic condition in the aquifer. Thus, the study helped in understanding the source and mobilization of arsenic in ground water. The findings based on isotope data in Bagalkot district of Karnataka show that the source of fluoride in ground water is geogenic as well as manmade and it is mostly due to leaching of fluoride from weathered granite, gneisses and pegmatities and partly from waste produced from the rock polishing industries located in the vicinity of Ilkal town.

Isotopes have been successfully used to identify the source of pollution in ground water of Raipur city, M.P.study shows that the leachate from waste disposal sites, landfills and dairy forms are contaminating the shallow aquifer. However, deep aquifers are free from contamination.  

 
 
 

Electrocatalytic CO2 Conversion to Oxalate by a Copper Complex

Global warming concern has dramatically increased interest in using CO2 as a feedstock for preparation of value-added compounds, thereby helping to reduce its atmospheric concentration. Here, we describe a dinuclear copper(I) complex that is oxidized in air by CO2 rather than O2; the product is a tetranuclear copper(II) complex containing two bridging CO2-derived oxalate groups. Treatment of the copper(II) oxalate complex in acetonitrile with a soluble lithium salt results in quantitative precipitation of lithium oxalate. The copper(II) complex can then be nearly quantitatively electrochemically reduced at a relatively accessible potential, regenerating the initial dinuclear copper(I) compound. Preliminary results demonstrate six turnovers (producing 12 equivalents of oxalate) during 7 hours of catalysis at an applied potential of –0.03 volts versus the normal hydrogen electrode.

WASTE WATER TREATMENT

The composition of municipal waste water varies from place to place.  Sometimes industrial wastes also mix with sewerage.  The type of treatment of wastewater thus depends upon its characteristics and the desired quality of water after treatment.  The wastewater treatment plants are generally primary, secondary or for advanced treatment.

The purpose of waste water treatment is to remove/reduce organic and inorganic substances, nutrients, toxic substances, kill pathogenic organisms, etc., so that the quality of discharged in some water body, on land or agricultural field.   Treatment of water thus aims at reduction of BOD, COD, eutrophication, etc., of receiving water bodies and prevention of bio-magnification of toxic substances in food chain and prevention of disease due to pathogenic organisms present in the waste water.

Primary treatment:  It is physical process for removal of debris, large particles with the help of screen.  The wastewater after screening is passed through grit chamber where sand, grit and other solids settle down.  The water is then passed through the sedimentation tank or clarifier where most of the suspended solids settle down due to gravity.  For better removal of suspended solids, sometimes chemically treated polymers are used.  About 35% BOD and 60% of suspended solids are removed during primary treatment.

Secondary treatment:  It is a biological process which involves microorganisms.  It removes up to 90% of the BOD and 90% of suspended solids. Bio degradable oxygen demanding wastes are stabilized. Following are the various approaches adopted in secondary treatment.

Tricking filters: these consist of a bed of crushed stones/pebbles covered with slime which consists of mainly of aerobic bacteria, algae, fungi, protozoa, worms and insect larvae. Sewage is degraded by the aerobic bacteria when it passes through the bed and is collected at the bottom of the filter. Some of the treated sewage may be re-circulated along the influent. It helps in better removal of organic matter and also keeps the filter moist when the flow rate over the filter is slow.

Activated sludge process: the effluent from the primary clarifier goes to aeration. Aeration tank also receives microorganisms from the secondary settling tank known as activated sludge. Oxygen is pumped into aeration tank for maintaining aerobic condition. After few hours of agitation, the waste water goes into secondary settling tank where solid settle at the bottom. The sludge is produced, dewatered and disposed off. This can be used for landfills or disposed off in a ocean or used in croplands, pastures, etc.

Rotating Biological Contactor (RBC):  It consists of circular plastic discs which are arranged on a rotating shaft.  Circular discs have microorganisms grown on them.  The discs are contained in a wastewater holding tank.   About 40% area of the discs is submerged in the tank.  The discs rotate in and out of water as the RBC rotates.  The microorganisms present on the discs absorb organic matter when they are in water and obtain the required oxygen when the discs are out of water.   Thus a high degree of organic matter removal is achieved. 

Advanced Sewage Treatment:  After the primary and secondary treatment many undesirable substances still remain in the effluent.   Advanced water treatment involves the removal of such substances.  The treatment, therefore, involves specific steps depending upon the type of substances to be removed.  The materials to be removed in such treatment may include nitrates and phosphates (which cause eutrophication of receiving waters), colour, bacteria, viruses, pesticides, toxic metals, etc.  Chlorination of water is generally done to kill harmful bacteria and some viruses.  However, chlorine can produce cancer-causing chlorinated hydrocarbons by reacting with organic matter.  Other, but costly methods of disinfection are the use of ultraviolet light and ozone treatment.  The sludge produced after such treatment is used as a fertilizer in the fields.  However, there are chances of toxic metals and other untreated substances to build up in the food chain or leach to the groundwater.

 
Conclusion and Remedies:
 
arrow Every small scale chemical factories /industries /leather processing system invariably should have RO system.
   
arrow The waste chemical water should go through pipeline so that the adjoined area will not be affected.
   
arrow The chemical recycling product should be used in other industries without creating waste.
   
arrow The available ground water resources should not be contaminated in future.
   
arrow In order to measure CO2, CHOs (Carbon Monoxide) one satellite has to be launched in the space by Tamil Nadu Scientists. 
   
arrow As per latest report, the Sulphur die oxide and Nitrogen di oxide has been controlled in Tamil Nadu when compared to other State, the air pollution is less. Quick/fast growth trees has to be planted in order to avoid plantation.
   
arrow Recycling of waste has to be utilized in industries/agriculture without creating further waste.
   
arrow No tree should be destroyed for future generation.
   
arrow Reduce sophisticated weapons in future.
   
arrow Any chemical content can be diluted by pure water.  For long term use without pollution, big gravel can be shrouded in annular area of well by digging ½ m depth so that the rain water will inject through Artifice Cap in order to dilute chemical substance in annular area of well upto bottom.   This kind of well design is required in order to avoid chemical pollution.
   
arrow Pure water injection method is not only increasing water level but also reducing chemical pollution.
   
arrow Pottasium permanganate, potash Alam (AL+3) bleaching powder can be utilized in order to purification well water for further utilization.
   
arrow In hard rock terrain, chemical pollution will not occur due to impact of rock.
   
arrow Rain water harvesting is essential due to acute water shortage but also required to dilution of chemical pollution. 
   
arrow Recycling of waste materials Is needed without creating further chemical pollution.
   
arrow If you go deeper aquifer in coastal area, saline water will enter into well due to over exploitation.
   
arrow Present condition of bore well/tube well can be identified by remote sending technology/remote sensing radar.
   
arrow “Elcross Camera” by which remote water resource can be identified.
   

Heat pump technology taps geo-thermal vents:   

Making a gene that allow a type of fern to tolerate high level of arsenic.  PURDUE University researchers hope to use the finding to create plants that can clean up soils and water contamination by the toxic metal.

Artificial fuel:

Produced from artificial cell which absorbs CO2 by solar system by which environmental pollution can be completely controlled.  It will happen in future after completion of research.

“GLOBAL WARMING IS A GLOBAL PROBLEM.
GLOBAL PROBLEMS NEED GLOBAL SOLUTION”

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