Paras R. Pujari

Assessment of the impact of on-site sanitation systems on groundwater pollution in two diverse geological settings—a case study from India

On-site sanitation has emerged as a preferred mode of sanitation in cities experiencing rapid urbanization due to the high cost involved in off-site sanitation which requires conventional sewerages. However, this practice has put severe stress on groundwater especially its quality. Under the above backdrop, a study has been undertaken to investigate the impact of on-site sanitation on quality of groundwater sources in two mega cities namely Indore and Kolkata which are situated in two different geological settings. The parameters for the studies are distance of groundwater source from place of sanitation, effect of summer and monsoon seasons, local hydro-geological conditions, and physico-chemical parameters. NO3 and fecal coliform concentrations are considered as main indexes of pollution in water. Out of many conclusions which can be made from this studies, one major conclusion is about the influence of on-site sanitation on groundwater quality is minimal in Kolkata, whereas it is significant in Indore. This difference is due to the difference in hydrogeological parameters of these two cities, Kolkata being on alluvium quaternary and Indore being on Deccan trap of Cretaceous to Paleogene age.

Impact assessment of on-site sanitation system on groundwater quality in alluvial settings: A case study from Lucknow city in North India

The present case study has been undertaken to investigate the impact of on-site sanitation on groundwater quality in alluvial settings in Lucknow City in India. The groundwater samples have been collected in the areas of Lucknow City where the on-site sanitation systems have been implemented. The groundwater samples have been analyzed for the major physicochemical parameters and fecal coliform. The results of analysis reveal that none of the groundwater samples exceeded the Bureau of Indian Standards (BIS) limits for all the parameters. Fecal coliform was not found in majority of the samples including those samples which were very close to the septic tank. The study area has a thick alluvium cover as a top layer which acts as a natural barrier for groundwater contamination from the on-site sanitation system. The t test has been performed to assess the seasonal effect on groundwater quality. The statistical t test implies that there is a significant effect of season on groundwater quality in the study area.

Impact of the disposal and re-use of fly ash on water quality: The case of the Koradi and Khaperkheda thermal power plants (Maharashtra, India)

An increasing amount of fly ash from thermal power plants is produced in India every year. Its disposal is generally done in ponds after it is mixed together in suitable proportion of water to form a slurry. Fly ash from Koradi and Khaperkheda thermal power plants (Nagpur, Maharashtra) is commonly disposed in an area characterized by the presence of many small villages where the population uses the groundwater for drinking and domestic purposes. Here, the groundwater locally exceeds the concentration limits recommended by the Bureau of Indian Standards (BIS, 2005) and by the World Health Organization (WHO, 2008) for Mg(2+), Ca(2+), NO3(-), SO4(2-), Total Dissolved Solids (TDS) and for some minor elements like As, Mo, V and U. A new geological map of the study area has been prepared to understand the possible water-rock interactions. An extensive geochemical survey of groundwater, stream water and fly ash was also carried out to clarify the possible origin of the pollutants by discriminating between geogenic and anthropogenic sources and to assess the influence of the ash ponds on water quality. The analytical results suggest that a large part of the sulfates in the groundwater of the villages of Masada, Khairi and Kawatha originate from the infiltration of industrial water from tens of factories that mix fly ash with relatively high quantities of gypsum and lime for the production of bricks. In addition, the interaction with the relatively U-rich Gondwana units, like Talchir formation, is probably the cause of the high concentration of this element. Results showed how the relatively high concentrations of Mo, As, B and F in circulating waters are linked to the leaching from fly ash, also pointing out a direct spatial correlation between the concentration of fluorides in the groundwater and their closeness to the ash ponds.

Ground penetrating radar (GPR) study to detect seepage pathways in the Ajanta Caves in India

The present study used the ground penetrating radar (GPR) tool to decipher the presence of fractures which may be possible pathways for seepage into the Ajanta Caves in India. GPR data were collected by 40- and 200-MHz antennas from Geophysical Survey Systems, Inc. (GSSI). The data were edited and processed using the RADAN 6.5 software. The processed data indicate the presence of fractures of varying orientation in the basaltic formations. The study shows high reflection zones indicative of fractures as well as strong absorbance zones which may be a homogeneous zone without any fractures.

Assessment of groundwater pollution from ash ponds using stable and unstable isotopes around the Koradi and Khaperkheda thermal power plants (Maharashtra, India).

The impact on local water resources due to fly ash produced in the Koradi and Khaperkheda thermal power plants (district of Nagpur, Maharashtra - India) and disposed in large ponds at the surface was assessed through the study of environmental variation of ratios of stable and unstable isotopes. Analyses of oxygen and hydrogen isotopes suggest scarce interaction between the water temporarily stored in the ponds and the groundwater in the study area. Data also highlight that the high salinity of groundwater measured in the polluted wells is not due to evaporation, but to subsequent infiltration of stream waters draining from the ponds to the local aquifer. (87)Sr/(86)Sr values, when associated with Sr/Ca ratios, demonstrate the dominant role of waste waters coming from tens of brick kilns surrounding the pond sulfate pollution. Uranium isotopic analyses clearly show evidence of the interaction between groundwater and aquifer rocks, and confirm again the low influence of ash ponds. A new conceptual model based on the study of the isotopes of radium is also proposed and used to estimate residence times of groundwater in the area. This model highlights that high salinity cannot be in any case attributed to a prolonged water-rock interaction, but is due to the influence of untreated waste water of domestic or brick kiln origin on the shallow and vulnerable aquifers.

A case study of On-site sanitation system on the quality of groundwater in hard rock terrain of Coimbatore city

The present case study has been undertaken to investigate the impact of On-site sanitation system on groundwater quality in the hard rock settings in Coimbatore city, India. Groundwater samples have been collected from the sites in Coimbatore city where the On-site sanitation systems are installed. The groundwater samples have been analysed for the major physico-chemical parameters and faecal coliform. Critical parameters considered in the analysis are namely nitrate, faecal coliforms and chloride. The presence of faecal coliform in bore wells indicates the contamination from On-site sanitation systems. A comparison of the present study with study carried out in the alluvial settings in India indicates that the contamination of groundwater in the hard rock areas is more as compared to the alluvial settings where On-site sanitation systems have been implemented. It is hypothesized that the secondary porosity in the hard rocks in the form of fractures leads to vulnerability of aquifer as compared to the porous sandy formations in the alluvial settings. It is desired that implementation of On-site sanitation systems in hard rock regions needs to be undertaken after detailed site specific hydrogeological studies.

Predicting impacts of climate variability on habitats of Hippophae salicifolia (D. Don) (Seabuckthorn) in Central Himalayas: Future challenges

Abstract Climate variability is the most influential driver altering the natural habitats of species leading to worldwide biodiversity loss. Understanding the climatic niche of vulnerable species and predicting its shift due to impending climate change is highly important to assess the damage. It also helps to plan and implement long term ex-situ or in-situ strategies to protect the species and its fragile habitats. Though, various important species of Himalayas are exploited for their economic and medicinal benefits, yet the impact of climate change on species have not been efficiently documented. Present study, is an attempt to understand the impact of climate vulnerability on habitat suitability of Hippophae salicifolia, a multipurpose species that grows particularly on the riparian fronts of river Ganga in Central Himalayas, using species distribution modeling. The Maximum entropy (MaxEnt) model with field observed occurrence locations of the species and CMIP5 (Couple Model Inter-comparison Project) derived bioclimatic variables were used for the study. The predictions were done on the geographic area of Central Himalayas in Uttarakhand state of India according to four IPCC RCPs (Intergovernmental Panel for Climate Change, Representative Concentration Pathways) for the future periods 2050 and 2070. Our results show that the estimated potential (threshold-1) area along the riparian fronts is around 2050 km2 for the current period. Whereas, for the future years, the suitable area is likely to be lost by 87% for all climate change scenarios making H. salicifolia highly vulnerable in it’ s actual habitats. An upward shift in the habitat of the species by 1700 m amsl (2800–4500 m amsl) is also predicted. Shift of species from its micro-habitats due to climate reflects unusual patterns and demands the vital need of applying climate adaptive management for habitat conservation. Present study presents a baseline database for broad-scale applicability of riparian front restoration for species conservation.

Impact of on-site sanitation systems on groundwater sources in a coastal aquifer in Chennai, India

On-site sanitation is the most preferred mode of sanitation due to expensive off-site sanitation. The increasing population especially in the peri-urban areas has led to increasing use of on-site sanitation systems in India. However, the habitations in the vicinity of these systems do not have centralised water supply and are dependent on groundwater sources. However, there is concern about leaching of faecal coliforms and nitrate from the septic tanks to the underlying aquifer. The present study is attempted at two sites in the coastal city of Chennai where on-site sanitation is prevailing. The sample locations (16 nos.) are selected in such a way that groundwater sources are situated in the vicinity of on-site sanitation systems. The groundwater sources are the bore wells installed by the private agencies. It is observed that parameters considered key parameters to study the impact of the on-site sanitation systems, namely Na2+, Cl−, NO3−, faecal coliform and total dissolved solids, exceed the concentration limits recommended by the Bureau of Indian Standards. The piper diagram analysis identifies that the predominant cations and anions are respectively Na+, and Cl−, SO4− and HCO3−.The Gibbs plot shows ground water quality is dominated by the evaporation process in both the seasons. The Cl/HCO3 ratio in many samples confirms the seawater intrusion in the study area. Elevated concentrations of faecal coliforms in all the samples (16 nos.) confirm the significant amount of groundwater pollution from the on-site sanitation systems. It is desired that policy planners and implementation agencies should undertake detailed scientific and hydrogeological studies of the region in order to examine the feasibility of implementing on-site sanitation systems.

2D Stabilised analytic signal method in DC pole-pole potential data interpretation

Using analytic signal method, interpretation of pole-pole secondary electric potentials due to 2D conductive/resistive prisms is presented. The estimated parameters are the location, lateral extent or width and depth to top surface of the prism. Forward modelling is attempted by 2D-Finite Difference method. The proposed stabilised analytic signal algorithm (RES2AS) uses Tikhonov’s regularization scheme and FFT routines. The algorithm is tested on three theoretical examples and field data from the campus of Roorkee University. The stability of RES2AS is also tested on synthetic error prone secondary pole-pole potential data.