water Article Water Quality Changes during the Initial Operating Phase of Riverbank Filtration Sites in Upper Egypt Rifaat Abdel Wahaab 1,2, Ahmed Salah 1 and Thomas Grischek 3,* 1 Holding Company for Water and Waste Water, 1200 Corniche El Nile, Rod-El-Farag, 12622 Cairo, Egypt; [email protected] (R.A.W.); [email protected] (A.S.) 2 Environmental Science Division, National Research Centre, 12622 Cairo, Egypt 3 Division of Water Sciences, University of Applied Sciences Dresden, 01069 Dresden, Germany * Correspondence: [email protected]; Tel.: +49-351-4623350 Received: 15 May 2019; Accepted: 13 June 2019; Published: 15 June 2019 Abstract: To meet the increasing water demand and to provide safe drinking water in Egypt, the Holding Company for Water and Wastewater (HCWW) and its affiliated companies have started a program to develop riverbank filtration (RBF) sites in all Egyptian governorates. The paper gives an overview of water quality changes as a result of RBF, during the initial phase of operation at three sites in Upper Egypt, between 2015 and 2018. Significant changes were observed for chloride, sulfate, iron, manganese, ammonium, and in the bacterial counts. After the initiation of pumping from the RBF wells, it took 2 to 8 months until stable water quality was observed for the hydrochemical parameters and 2 to 14 months for the microbiological parameters. The results showed that RBF wells should be operated continuously, to maintain the advantage of lower Fe and Mn concentrations achieved by the wash-out effect in the aquifer zone, between the river bank and the RBF wells. Keywords: riverbank filtration; water quality; bank filtrate portion; iron; manganese; microorganisms; system costs 1. Introduction Egypt’s freshwater consumption is growing ten times faster than its freshwater production [1], and the current ballooning demographics show no sign of abating any time soon. The total population of Egypt increased from 22 million in 1950 to around 88 million in 2015 [2]. This rapid increase in population growth will continue for decades to come and it is likely to increase to between 120–150 million, by 2050. A high population growth rate would exaggerate the problems associated with water allocation. Egypt is not only facing problems with an increase in water demand but also with pollution of the River Nile water through industrial, agricultural and municipal inflows. In Egypt, large amounts of untreated or poorly treated sewage are discharged into surface waters [3]. Along the River Nile, there are a total of 56 large drains that discharge water and transfer pollutants from industrial and settlement areas, and 72 drains that discharge water mainly from agricultural areas. The exports from agricultural areas and domestic wastes are considered to be the main sources of water pollutants in the River Nile [4]. The water quality of the River Nile mainly depends on the water quality in the Lake Nasser reservoir and the volume of water released from it. Despite the overall water quality of the River Nile being suitable for drinking water production using conventional treatment, accidental (oil) spills and flash floods occur frequently, which affect the operations of water treatment plants [5]. Additionally, from December to January, irrigation canals are put under maintenance (winter closure) and the water released from the Aswan dam is reduced, such that less dilution of sewage inputs occur, and some large water treatment plants suffer from higher siltation at the intake points. During this Water 2019, 11, 1258; doi:10.3390/w11061258 www.mdpi.com/journal/water Water 2019, 11, x FOR PEER REVIEW 2 of 18 Water 2019, 11, 1258 2 of 18 dilution of sewage inputs occur, and some large water treatment plants suffer from higher siltation at the intake points. During this period, several small surface water abstraction units suffer from the period,lower river several water small level surface and use water that abstraction time for maintenance, units suffer fromresulting the lower in a decrease river water in drinking level and water use thatsupply time [6]. for maintenance, resulting in a decrease in drinking water supply [6]. EgyptEgypt relies relies on on the the River River Nile Nile for 95% for of95% its freshwaterof its freshwater needs for needs irrigation, for irrigation, drinking, anddrinking, industrial and purposes.industrial Egypt’spurposes. aquifers, Egypt’s which aquifers, contain which large contain amounts large of amounts fossil water of fossil that experienceswater that experiences little to no replenishment,little to no replenishment, cannot be abstracted cannot be easily.abstracted Additionally, easily. Additionally, while desalination while desalination of seawater of isseawater slowly pickingis slowly up inpicking the country, up in itthe still country, represents it astill very represents negligible a amount very negligible of freshwater amount production of freshwater overall, andproduction comes with overall, its ownand setcomes of environmentalwith its own set issues. of environmental New strategies issues. have New to be strategies developed have by to the be governoratesdeveloped by to the overcome governorates the water to overcome shortage. the One water strategy shortage. is to One opt strategy for riverbank is to opt filtration for riverbank (RBF), whichfiltration has (RBF), been used which for has over been 150 used years for in over Germany 150 years and otherin Germany European and countries, other European to produce countries, large quantitiesto produce of large drinking quantities and industrial of drinking water and with industrial low cost water and highwith quality,low cost even and duringhigh quality, floods even and droughtsduring floods [7]. and droughts [7]. RiverbankRiverbank filtrationfiltration is is the the abstractionabstraction ofof waterwater fromfrom aquifersaquifers thatthat areare hydraulicallyhydraulically connectedconnected to to thethe river, river, through through pumping pumping wells wells adjacent adjacent to theto riverthe river [8]. The[8]. pumpingThe pumping lowers lowers the groundwater the groundwater table, suchtable, that such the that river the water river infiltrates water infiltrates into the into aquifer. the aquifer. The bank The filtrate bank percolates filtrate percolates through through the aquifer the sedimentsaquifer sediments towards towards the production the production wells, where wells, it wh mixesere withit mixes groundwater. with groundwater. Figure1 showsFigure an1 shows RBF cross-sectionan RBF cross-section with typical with conditions typical conditions from Upper from Egypt. Upper Favorable Egypt. Favorable conditions conditions include a good include hydraulic a good connectionhydraulic betweenconnection the between river and the aquifer,river and erosive the aquifer, river flow erosive conditions river to flow prevent conditions riverbed to clogging, prevent suriverbedfficient aquiferclogging, thickness sufficient (> 10aquifer m) and thickness hydraulic (>10 conductivity m) and hydraulic (K > 1 conductivity10 4 m/s), and (K > a 1 low × 10 natural−4 m/s), × − (pre-RBF)and a low gradient natural (pre-RBF) of groundwater gradient flow of groundwater towards the riverflow [towards8–10]. Such the river favorable [8–10]. hydrogeological Such favorable conditionshydrogeological for RBF conditions have been for identified RBF have for been Upper identified Egypt [ 11for]. Upper Egypt [11]. FigureFigure 1. 1.A A generalized generalized riverbank riverbank filtration filtration (RBF) (RBF) cross-section cross-section with with typical typical conditions conditions for Upper for EgyptUpper ©EgyptGrischek, ©Grischek, HTW Dresden. HTW Dresden. TheThe technology technology in in itself itself is is quite quite simple, simple, is cheaperis cheaper than than conventional conventional water water treatment treatment systems, systems, and requiresand requires little maintenance. little maintenance. Identifying Identifying the right locationthe right for location an RBF sitefor is an a key RBF issue. site Therefore,is a key waterissue. qualityTherefore, tests water of river quality and groundwater tests of river need and togroundwater be conducted need at each to be specific conducted site, andat each the compositionspecific site, ofand the the riverbed composition and thickness of the riverbed and hydraulic and thickness conductivity and hydraulic of the adjacent conductivity aquifer of need the adjacent to be examined aquifer toneed assess to be the examined viability ofto aassess site. Ifthe an viability RBF scheme of a si iste. properly If an RBF designed, scheme the is properly subsurface designed, passage the of surfacesubsurface water passage through of the surface riverbed wa andter through aquifer material the riverbed provides and several aquifer natural material treatment provides processes, several includingnatural treatment filtration, processes, biodegradation, including adsorption, filtration, chemicalbiodegradation, precipitation, adsorption, and improvementchemical precipitation, of water qualityand improvement through redox of water processes quality [12 ].through redox processes [12]. AccordingAccording to to [ 13[13],], four four stages stages of of site site investigation investigation should should be be followed: followed: 1.1. InitialInitial sitesite assessment,assessment, includingincluding visualvisual reconnaissancereconnaissance byby sitesite visits,visits, documentationdocumentation ofof verbalverbal andand archivedarchived information,information,