Certain Implications of Oxic Conditions in Alluvial Groundwater

Milan Dimkić1, Milenko Pušić2, Brankica Majkić-Dursun1, Vesna Obradović1

1 Jaroslav Černi Institute for Development of Water Resources, 80 Jaroslav Černi Str., 11226 Pinosava - Belgrade, Serbia; This e-mail address is being protected from spambots. You need JavaScript enabled to view it
2 Faculty for Mining and Geology, Department for Hydrogeology, 7 Djusina Str., 11000 Belgrade, Serbia; This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Abstract

Alluvial deposits are important bearers of groundwater, which is used for potable water supply. The bank filtration method has an important application in groundwater production. The greatest significance for the baseline quality and transformation of groundwater in these aquifers, from the river to the well, is its degree of oxicity. This paper gives an overview of the processes which define the baseline quality and transformation of groundwater quality, the conditions of oxicity and the biochemical processes of nitrification and denitrification, reduction and oxidation of iron and manganese, and reduction and oxidation of sulfur. Oxic conditions also determine the character and rate of well ageing in alluvial aquifers. Testing in wells of the Belgrade groundwater source indicates a dominant process of clogging with iron deposits. Changes in local hydraulic resistance in well screens, which appear as a result of clogging, are linked to the causes, i.e. the main indicators: the redox potential and the content of ferrous iron. Also, the conclusion is that long-term operation and design of wells in anoxic groundwater is dependant on biochemical processes. For wells in conditions of high oxicity, filtration stability and maintaining a laminar regime of groundwater filtration are important criteria.

Keywords: groundwater, alluvial aquifer, groundwater oxicity, well ageing

 

 

Introduction

Groundwater represents the largest accumulation of fresh water in the world, and accounts for over 97% of the total fresh water on planet Earth (not including glaciers and permafrost). The remaining 3% is mainly comprised of surface waters (lakes, rivers, marshes) and soil moisture. Groundwater maintains river levels in periods of low water, and a large number of ecosystems.

It is estimated that over 50% of the water supply in the world comes from groundwater, and in Europe, this figure is over 60%. In Serbia, around 70 % of the water supply comes from groundwater (Dimkić et al., 2007a) of which over 50% comes from alluvial aquifers. In Germany, based on the data from 2003 (Schmidt et al., 2003),

it is noted that the most of the potable water is supplied through bank filtration; more than 300 water works use bank filtration and roughly 50 plants are based on artificial groundwater recharge. Through the application of bank filtration and artificial recharge, water is additionally purified by filtration through the aquifer, which is a very important addition to the treatment of river water and decreases the risk of accidental pollution.

Alluvial groundwater also owes its “popularity” to its availability, i.e. its proximity to the place where it is utilized.In Figure 1, alluvial formations are not visible. Their thickness (usually less than 100m) represents an insignificant part of the Earth’s diameter. However, their significance for humans and the entire living world is considerable.