Groundwater Degradation and Remediation in the Nile Delta Aquifer

Abstract

Groundwater quality is increasingly being threatened by agricultural, urban, and industrial wastes, which leach or are injected into underlying aquifers. Groundwater pollution can occur from on-site sanitation systems, landfills, effluent from wastewater treatment plants, leaking sewers, petroleum stations, or from over-application of fertilizers in agriculture. Pollution can also occur from naturally occurring contaminants, such as arsenic or fluoride. Aquifer vulnerability to pollution is mainly related to the use of excess fertilizers, due to the growing industrial activities; sewage effluent disposal; and landfill leaching, gasoline plumes, and nuclear wastes. Contaminants found in groundwater cover a broad range of physical, inorganic chemical, organic chemical, bacteriological, and radioactive parameters. Different mechanisms influence the transport of pollutants (e.g., diffusion, adsorption, precipitation, decay, in the groundwater). Movement of water and dispersion within the aquifer spreads the pollutant over a wider area. Once the groundwater is contaminated, its quality cannot be restored by stopping the pollutants at the source. Groundwater monitoring networks are constructed to perform site monitoring, ambient groundwater quality monitoring, and to collect data to develop groundwater aquifers, or initiate site remediation. The locations and depths of monitoring wells are the most important aspects of a monitoring network. Groundwater contaminants are subjected to dispersion and diffusion. The water quality index (WQI) is one of the most effective tools to communicate information on the quality of water to the concerned citizens and policy makers. Mathematical modeling techniques have been successfully utilized for simulating groundwater movement and solute transport mechanism. Hydrochemical and isotope tracer methods have been successfully used to assess pollution sources and concentrations in groundwater problems. Selection of the appropriate remedial technology is based on site-specific factors and often takes into account cleanup goals based on predicted potential risk to human health and the environment. Contaminated site remediation is generally difficult, time consuming, and expensive. Groundwater remediation is the cleanup of contaminated groundwater to levels that are in compliance with regulatory limits set by the Environmental Protection Agency (EPA). Recently, many activities have had an impact on eutrophication, contamination status, ecological value, and the environmental condition of the Nile Delta region. This chapter aims to identify problems, knowledge gaps, and needs that are deemed important to improving groundwater monitoring, modeling, and remediation in the Nile Delta.