Natural water purification and water management by artificial groundwater recharge

Balke et al.1J Zhejiang Univ SciB 2008 9()22221Joumal of Zhejang Universily SCIENCE BISSN 1673-1581 (Print; ISSN 1862-1783 (Onlina)www.zlu.edu.cn/jzue; www.springerlink.comE-mail: jus@zju.edu.cnJZUS'Review:Natural water purification and water managementby artificial groundwater rechargeKlaus-Dieter BALKE, Yan ZHU(Instiute for Geosciences, University of Tibingen, Sigwarst. 10, D-72076 Tubingen, Germany)E-mail: klaus deter.balke@umi. tuebingen.deReccived Dec. 24, 2007; revision acepted Jan. 17, 2008Abstract: Worldwide, several regions suffer from water scarcity and contamination. The infiltration and subsurface storage ofrain and river water can reduce water stress. Atificial groundwater recharge, possibly combined with bank filration, plant puri-fication and/or the use of subsurface dams and artificial aquifers, is especially advantageous in areas where layers of gravel andsand exist below the earth's surface. Artificial infiltration of surface water into the uppermost aquifer has qualitative and quanti-tative advantages. The contamination of infiltrated river water will be reduced by natural attenuation. Clay minerals, iron hy-droxide and humic matter as well as microorganisms located in the subsurface have high decontamination capacities. By this, afinal water treatment, if necessary, becomes much easier and cheaper. The quantitative ffect concems the seasonally changingriver discharge that infuences the possibilit of water extraction for drinking water purposes. Such changes can be equalised byseasonally adapted infiltration/extraction of water in/out of the aquifer according to the river discharge and the water need. Thismethod enables a continuous water supply over the whole year. Generally, arifially recharged groundwater is better protectedagainst pollution than surface waler, and the delimitation of water protection zones makes it even more save.Key words: Artificial groundwater recharge, Natural attenuation, Water managementdoi:10.1631jzus.B0710635Document code: ACLC number: X52INTRODUCTIONARTIFICIAL GROUNDWATER RECHARGEThe growing population and an increase of in-Artificial groundwater recharge is the infiltrationdustrialisation and agricultural production in numer-of surface water into shallow aquifers to increase theous countries require more and more water of ade-quantity of water stored in the subsurface and to im-quate quality. In many regions there is a lack of sur-prove its quality by processes of natural attenuationface water and severe water contamination is to be(Balke et al, 2000). It can be practiced especially infound. Shallow groundwater resources are often ofriver valleys and sedimentary plains by infitratinginsufficient quality and over-exploited. Therefore, itriver or lake water into shallow sand and gravel layers.is of high priority to take into consideration all theThe infltration technique is chosen according to theproved water techniques that could help to reduce thehydrogeological conditions, the available groundexisting disaster.space, the water need, the composition of the infil-Artificial groundwater recharge is an approvedtrated water, and the degree of purification to bemethod that has been improved during the last dec-achieved (Schmidt, 1980; Schmidt and Balke, 1980;ades. It has been found that also the new kinds of1985). In order to improve the efficiency of naturalpolluting agents, especially organic compounds, canpurifica中国煤i-rface, arifcialbe minimized or even removed by natural purificationground煤化工ombined withprocesses in the subsurface.pre-treaTYHCN M H Gt purification,222Balke ot al. 1J Zhjiang Univ Sal B 2008 93)221-226subsurface dams and artificial aquifers (Balke et al, In this way, contaminating ions can also be fixed at2000; PreuB and Schulte-Ebbert, 2000).underground.The forming of ionic and molecular complexesNatural purification processeschanges the solubility, precipitation and sorption ofSurface water contains inorganic and organicsubstances such as heavy metals and organic com-compounds of natural origin as suspended matter andpounds.dissolved substances. In most cases, water in river andWithin the layer of filter sand and the aquifer, alake is contaminated by waste, sewage, chemicals,great variety of natural microorganisms exist, whichhydrocarbons, medicine, hormones, antibiotics, bac-are highly involved in rehabilitation processes (Balketeria, viruses, fertilizers, plant-protective agents, etc.and Griebler, 2003). Biodegradation, the decay ofand their decay products (Balke, 1990; 2003; Balke organic compounds by microorganisms, reduces theand Zhu, 2003; Remmler and Schulte- Ebbert, 2003).amount of organics, no matter they are of naturalFor drinking purposes, the contaminations in water.origin or stemming from contaminations.must be removed or destroyed by purifying processesThe community of purifying organisms mainlyas completely as possible.consists of autochthonous bacteria, protozoa anNatural punification effects within filter layersmetazoa. The group of protozoa includes flagellates,and in the subsurface are caused mainly by filtration,ciliates, amoebas, etc., and the group of metazoa in-sedimentation, precipitation, oxidation-reduction, sorp-cludes worms, nematodes, annelids and arthropods.tion-desorption, ion-exchange and biodegradation.The density of this population of organisms decreases,In plants for artificial groundwater recharge, theas well as the removal efficiency (Fig.1).water being infiltrated at first passes an artificiallyFilter bedMain processesinstalled layer of filter sand. This filter layer retainsRemoval“Tlooaing 2001; Precipitation,coarser particles by filtration.efiecen. sfeesate ! sdimentationChemical reactions between infiltrated water,.Top layerwith high activiessolid inorganic and organic substances in the sub-Sedincntaion,surface, and the groundwater flowing towards theFilter passage， mcchanical straining,extraction well may cause precipitation of sparinglywith lowcer activitiessorption. biodegrada-tionsoluble carbonates, hydroxides and sulphides-governed by pH-value and redox-potential- -withinthe filter layer and the aquifer.i Linderground passge. ) Continuation of，purificationThe oxygen content of the water is decisive for几E I rocsessoxidation processes and activities of microorganisms.The presence of reducing substances such as humicFig,1 Purification process during vrtical infitrationmatter, causing a lack of oxygen, is responsible forof water (PreuB and Schulte-Ebbert, 2000)chemical reductions. pH-value and redox-potentialinfluence these reactions, too.Allochthonous microorganisms, especiallyDissolved compounds, among them also con- pathogenous bacteria such as Salmonellae, Le-taminants, can be adsorbed especially by clay miner- gionellae, Streptococcus, Vibrio cholerae, Es-als, iron-hydroxides, amorphous silicic acid, and cherichia coli, and endangering viruses such asorganic substances. If the chemical composition ofhepatitis-A and -B, poliomyelitis, etc. that have beenthe water changes, desorption may happen.introduced into the subsurface by the seepage ofIon exchange processes take place mainly in thecontaminated water or sewage, are normally elimi-presence of organic matter and clay minerals. One nated after a certain period of time.kind of ion is exchanged against another inIn order to reduce the danger of groundwaterstoichiometric relation, e.g,contathe groundwaterrechal中国煤化工s to be poeteCa2*A^-+2Na*←Na*A-+Ca2*.by gr(:TYHCNMHGBalke et al.1J Zhejiang Univ Sci B 2008 9()22626223Techniques of artificial groundwater rechargewith mean river water discharge and mean ground-Water can be infiltrated into aquifers with the water levels (Curve a in Fig.4), as much water can behelp of basins, pipes, ditches and wells (Balke, 2004).infiltrated and naturally purified as needed by theInfiltration basins (Fig.2) positioned above an consumers. With regard to later periods with low riveraquifer with sufficient hydraulic permeability oftenwater discharge, a surplus of water can be infiltratedhave sizes ranging from 100 to 10000 m2. Theinto the aquifer. This operation during periods withthickness of the uppermost layer of filter sand rangesmean and high river water discharges increases thefrom 50 to 100 cm, and the grain size should be lessamount of stored water that is documented by a risingthan 3 mm. The water to be infiltrated passes over a groundwater level (Curve b in Fig.4).cascade in order to enrich its oxygen content, Then itpercolates the sand filter and the unsaturated zone andInfiltrationbasinfinally reaches the groundwater table. The slopes ofψinfiltration basins can be stabilized with concreteparts or designed in a natural mode.River- InflovWellBiological lawnFihter SandFig.4 Maoagement of water storage and avilaility,the lines represent the river water and the appertaininggroundwater levelsDuring periods with low river water dischargeFig.2 Cross section of an infiltration basin with cascadeand a reduced possibility to infiltrate river water, the(ORLETHZ, 1970)water stored underground by former infilration andeven a surplus can be pumped out. By this, theThe quantitative efficiency of the filter sandgroundwater level can be lowered from Phase b tolayer is influenced by the permeability of the flterPhase c (Curve c in Fig.4), according to the thicknesssand, the mode of rain fall, the growing u of algae, of the aquifer and the depth of the well. In this way itetc. The rate of filtration drops in the course of time,is possible to manage the water supply. Besides, in theand after a certain period the filter layer must becase of extreme river water contamination bycleaned or replaced.chemical accidents or ship collisions, the withdrawalA plant for artificial groundwater recharge con-from the river can be stopped temporarily until thesists of a source of surface water, a pump station, anhighly contaminated water passed away.infiltration basin and extraction wells (Fig.3).For the infiltration of smaller quantities of water,infiltration pipes, surrounded by filter sand and lo-cated 1 to 3 m below the earth's surface, can be used(Fig.5a); for bigger quantities of water, infiltrationgalleries are recommended (Fig.5b).而+ To consumersinilration basins(a)(b)Fig.3 Scheme of artificial groundwater recharge by in-fltration basins. (a) Profle; (b) Map (ORL-ETHZ, 1970)Besides the purification effects, artificial中国煤化工，groundwater recharge also enables a better waterYHC N M H G (ORL-ETHZ,management (Zhu and Balke, 2005). During periods 1970). (a) nuraoon pipes; (D) inuntration glleries224Balke ot al. 1J Zhejang Unv Sci B 2008 93):221-226In many cases, infiltration ditches, flled withExample: Waterwork Wiesbaden- Schierstein,filter sand, are applied with lengths between 10 and Germany100 m, width ofca. 1 m, and depths of4 to 6 m (Fig.6).The Waterwork Wiesbaden Schierstein, Ger-many, is an example of a plant applying artificial。lnflow、groundwater recharge by using infiltration basins,infiltration wells, infiltration pipes and extractionwells in connection with water treatment plantsGrain size(Fig.8). The raw water is extracted from the Rhine0.5~1.5 mmRiver. It passes a sedimentation basin, a cascade and6.0'mflows into infiltration basins. A certain part of thewater is pumped to a water treatment plant, treated byflocculation and filtration, and then infiltrated into1.0mFig.6 Scheme of an infltration ditch (Wolters andthe aquifer by infiltration wells and infiltration pipes.Hantke, 1982)After a subsurface passage, the artificially rechargedgroundwater is extracted from the aquifer by wells.Often infiltration wells are in use, dug wellsFinally, a rapid sand filtration and a slight addition of(Fig.7a) for sallow aquifers and dildl wells (Fig.7b) chlorine dioxide, in order to avoid a growing up offor deeper located aquifers.microorganisms in the distribution network, com-plete the water treatment.But it has to be taken into consideration thatnormally it is sufficient to use only one infiltrationand purification technique, and a final water treat-ment with chlorine dioxide (C102) can be added incases of emergency. In order to increase the effi-ciency of the system, especially in cases of increasedpollution of the surface water, it can be useful to(ab)combine artificial groundwater recharge with someFig.7 Dug well (a) and drilled well (b) for infiltrationother techniques of water treatment by natural puri-(ORL-ETHZ, 1970)fication.Calciun byroxide原Rhine watertreatment plantFeric chlorideSludgeIqC①④口⑤D9口1: Intake crib价oitrationgauieryB12: Acraion! Chlorinedioxide4: Sctling hasin13: Powdered carbon feede5: Infilration basin14: Rapid fhtration6: Flocculation15: Post-aeration.: Backwash basin8:Activated carbon filter 17: Slorn-sand filherCroundwaterMains supply9: Infilration well18: Drinking water tank中国煤化工.MH..CNMHG..Fig.8 Water course during the artificial and natural treatment(rr auts mun nt IeouauCU-OCUIct suein, Germany)Balke et al. 1J Zhejiang Univ Sci B 2008 9(3)221-226225PRE-FILTRATIONof 10 to 50 m length. The screens can be positionedbelow the river or lake. With such wells large quan-Pre-filtration is the filtration of water before thetities of water can be extracted.artificial groundwater recharge. It takes place inshallow basins with an impermeable bottom made,e.g., ofconcrete, which are flled with a layer ofgravel PLANT PURIFICATION PLANTSand sand of about 1 m thickness as filter material.Entering over a cascade, the water flows horizontallyA plant purification plant consists of shallowthrough the filter layer to a collector pipe located at thebasins that are equipped with special aquatic plants.opposite side of the basin. During the passage, the The purification of more or less polluted waterpurification processes described in Section 2 takeflowing through the basins is executed by bacteriaplace. Finally, the water is conducted to slow sand that are located at the roots of the aquatic plants andfilration basins where artificial groundwater rechargewithin the soil. Because a relatively large area ishappens by vertical seepage of the water.needed for such a treatment, a combination with arti-ficial groundwater recharge is possible but restrictedto cases with small water need.BANK FILTRATIONArtificial bank fltration (Fig.9) is the extraction SUBSURFACE DAMSof river or lake water by wells that are located near thebank of the surface water (Firch and Wichmann,In regions with dry seasons it may be advanta-2005). At adjusted pumping rates, the hydraulic gra-geous to construct a subsurface dam for the storage ofdient between the surface water level and the lowered the groundwater contained in the unconsolidatedgroundwater level at the well is directed towards therocks below an ephemeral river (Fig.10). Especiallywell. In this way, surface water is forced to flow into in narrow river valleys where loose sediments of sandthe aquifer and finally into the well. The well extracts and gravel are underlain by more or less imperviousa mixture of surface water and groundwater.bedrock in shallow depths, this method can be veryadvantageous.Subsurface damExtrnitionBerceFig.9 Scheme of bank fltrationThe portion of surface water that contributes to_Wadjithe extracted water depends on the permeability oftheriver bed and the aquifer. The quality of the extractedwater as a mixture of surface water and groundwateris especially influenced by the properties of the sur-Extraction Infilrationface water and the efficiency of natural attenuationwellduring the passage in the subsurface. The purificationSubsurface darprocesses are the same as described in Subsection 2.1.For the extraction of surface water also collector中国煤化工wells can be applied. They consist of a shaft of2 to 5MHCNM H G.; damm in diameter and horizontally installed screen strings226Balke et al.1J Zhejiang Univ SciB 2008 93);221-226The subsurface barrier can be build up withReferencesbricks or concrete. The upper crest of the dam shouldBalke, K.D， 1990. Investigation of the Groundwaterbe located about 1 m below the level of the river bed.Resources in the Irigation Area West of Ismaili/Egypt.Part , Vol. 4, ISBN 3-443-01014-8, Stuttgart (inUpstream the subsurface dam, a discharge well has toGerman).be located and, if water can be brought up from ad-Balke, K.D, 2003. Surplus or Absence of Chemical Compo-jacent areas, infiltration wells may be added.nents in Water and Its Consequences for Public Health Im:Balke, K.D, Zhu, Y. (Eds.), Water and Development.ISBN 7-116-03831-0/X17, Geology Press, Beijing,ARTIFICIAL AQUIFERSChina, p.36-42.Balke, K.D, 2004. Water Supply by Bank Filtration andArtificial Groundwater Recharge. In: Balke, K.D, Zhu,In mountainous areas artificial aquifers can beY, Prinz, D. (Eds), Water and Development I. ISBNestablished in narrow valleys of brooks and rivers.7-1 16-04217-2, Geology Press, Beijing, China, p.18-25.For this purpose, small dams of 3 to 5 m height areBalke, K.D., Griebler, C, 2003. Groundwater Use andbuilt up in the valley for retaining sediment which isGroundwater Protection. In: Griebler, C, Mosslacher, F.transported by the river during flood periods. After(Eds.), Groundwater Ecology. Facultas UTB, ISBNthe open space upwards the dam is filed up with sand3-8252-2111-3, Wien, p.495 (m German).and gravel, the water stored in the pore space of thisBalke, K.D, Zhu, Y, 2003. Sources of Water Pollution. In:Balke, K.D., Zhu, Y. (Eds.), Water and Development.sediment can be used. Compared with an open waterISBN 7-116-03831-0/X.17， Geology Press, Bejingreservoir, the storage capacity is reduced to 20%~China, p.3-9.30% of the whole space. But on the other hand,Balke, K.D, Beims, U, Heers, F.W, Hoelting, B., Hom-evaporation is reduced and water can be stored for arighausen, R, Matthess, G, 2000. Groundwater Exploi-longer period. Discharge pipes with valves installedtation. Hydrogeological Textbook. Vol. 4, Berlin-Stuttgart,in the dam at different levels, allow the withdrawal ofp.740 (in German).water in a controlled way and adjusted to the need.Firch, M., Wichmann, K., 2005. Infuence of Limiting Factorsupon the Purification Capacity of an Optimized Bank Fil-tration. Final Report of the Project B5 of theBMBF-Research Project Export-Oriented Research andCONCLUSIONDevelopment in the Field of Water Supply and Sewage.Part 1: Drinking Water. Technical University Ham-Artificial groundwater recharge is practiced forburg-Harburg (in German).many purposes: drinking water production, im-ORL-ETHZ (Swiss TechnicalUniversity，Zuerich,provement of raw water quality, storage of fresh wa-Switzerland), 1970. Guideline for Artificial Groundwaterter, aquifer recovery, infitration of storm water run-Recharge. Zuerich, p.516023 (in German).off, preservation of natural wetland, disposal ofPreuB, G, Schulte-Ebbert, U, 2000. Artificial GroundwaterRecharge and Bankfitration. Im: Rehm, HJ, Reed, Gtreated sewage effluents, formation of hydraulic bar-(Eds.), Biotechnology. Vol. 11c, Wiley-VCH, Weinheim,riers against sea water intrusion.p.425-444.Atificial groundwater recharge is a successfulRemmler, F, Schulte _Ebbert, U, 2003. Development of um-method in order to purify surface water and to im-derstanding the process of self-purification of groundwater.prove the water management. The great variability ofVom Wasser, 101:77-90 (in Cerman).infiltration, extraction and purification methods al-Schmidt, H., 1980. Groundwater Recharge and Water Produc-lows several combinations and adapted designs fortion. Zbl. Bakt. Hyg. I, Abt. Orig. B, p.134-155 (in Cer-various hydrological, hydrogeological and hydro-Schmidt, H, Balke, K.D, 1980. Possiblities of artificialchemical situations as well as for various water re-groundwater recharge and storage in the Federal Republicquirements.of Germany. Z DL. Geol. Ges, 131:93-109 (in Cerman),Compared with other methods of water treat- Schmidt, H, Balke, K.D, 1985. Requirements andment, artificial groundwater recharge is ecologicallyRegistration of Sites for Atificial Groundwater Rechargesustainable and cheaper than chemically inducedin the Federal Republic of Germany. UBA-FB 80-179,coagulation, ozone floc filtration, the application ofWolters, N, Hantike, H, 1982. Experiments with ifitrationBerlin, p.186 (in Cerman).reverse osmosis, ultraviolet beams, ultra-filtration, oractivated charcoal.中国煤化工DWKBlletin,Artificial groundwater recharge has proved very:rating Approach t如osuccessful at many sites in Germany over a period ofYH. C N M H GrneCoasta Aresmore than 100 years.of China, Proceedings Con. Soil. Bordeaux, p.301-305.