Wetland systems in the Alexander watershed for the improvement of water quality


In the past, natural wetland habitats were part of the natural landscape in some areas in Israel, mostly the coastal plain. However, most of these habitats have been lost due to anthropogenic development, mainly draining to expand the lands available for agriculture use (Green M, 1996). In the Alexander watershed, which used to be filled with natural wetlands (Sever, personal Communication), very few natural wetland areas remain. (Juanico M and Friedler E, 1995).


Constructed wetlands have been very successful in the last few decades for artificial treatment of wastewater and low quality water from different sources.   Technically, “constructed wetlands" have been defined as "manmade complexes of saturated substrate, emergent and submerged vegetation, animal life and water that simulate natural wetlands for human use and benefits” (Green M, 1996). The removal of different pollutants in the wetland system is based on natural processes with the aid of either macrophytes, or different water plants, floating or submerged (Ran N, 2004).   The removal of pollutants is either biological, chemical or physical and includes the following processes: physical sedimentation, organic matter dissolution, adsorption, filtration, burial in the sediments, nitrifaction/denitrfication and other microbial processes (Ran N, 2004; Avnon A and Laila Y, 2001).


Two main types of wetland systems exist. These are the free water surface (FWS) and sub-surface flow (SSF). In FWS, high hydraulic efficiency and good settling conditions contribute to high removal of organic matter and suspended solids. In SSF, processes within the soil contribute to high removal of phosphorus, nitrogen and heavy metals(Ran N, 2004).


While still relatively rare, wetland systems are currently used in Israel for treating wastewater from different sources and qualities.  Examples of such wetlands are a wetland in Noat-Smadar, designed to receive domestic and agriculture effluents or the wetland at Kibbutz Lahav designed to bring domestic and animal culture effluents to a level that enables irrigation (Gafni A, 1999). More recent examples are the wetland planned in Kibbutz Lotan designed to supply water for a birdwatchers park and  wetlands already built in gas stations around the country to treat the runoff. Another wetland, was built adjacent the Seven Mill Dam in the Yarkon Stream has been purifying some of the stream water since 2004 (Cohen 2006).


This chapter evaluates the function and the future implications of such artificial wetlands for the restoration of the Alexander stream in particular and for stream restoration in other Israeli streams. 


Kibbutz Maabarot Experimental Wetland System (based on:(Goren A, 2006).

The wetland system is located in the area of Kibbutz Maabarot, on an area of one and a half Donam, between the Road Number 4 to the east and the Alexander stream in the North.  A water pump located in the Alexander stream at Maabarot Park takes water from the stream every two hours for a period of twenty minutes, so that the approximate amount of water entering the wetland system amounts to about 534 liter/hour. The pump transfers the water to the pre-treatment area. The pre-treatment stage in the wetland comprises of a 6 meters diameter and 1.2 meter deep pool used as a sedimentation pond following a treatment using the FWS system. After a residue time of about 15 hours in this part of the system, the water flows out to the next stage using a perforated hose. Hyacinth plants with intensive root systems float in this pool, and take part in the water purification system. 


From this system, the water continues to a SSF system comprised of two sections : a smaller section with a surface area of 225 meters and  a residue time of 3.5 hours, and the larger section , with a residue time of  3.5 days. In larger section, many plant species grow including Willow, Purple Loosestrife, Common Reed, Nile Pypyrus and southern Cat-Tail. These plant species were either taken from natural wetland in the watershed or from the local plant nursery, and it includes both local and exotic plant species. Species were planted arbitrarily within the system and without any consideration of plant density. After this stage, the water is discharged from the collection hose at approximately 410 liters/hour and is returned to the stream.


Wetland sampling:

In order to assess the effectiveness of constructed wetlands as a treatment option, sampling of the wetland was carried out three times. The sampling program included measuring chemical concentrations from the inlet to the system (Alexander Stream), the sedimentation pool with the Hyacinth plants and the outlet of the system. The second sampling event was carried out a month later and included two sample sets during the day (21:00 p.m. and 9:00 a.m.), taken from the inlet, outlet, sedimentation pool and a point located at center of the  SSF system. A variety of water parameters were analyzed for the water samples including: BOD, COD, TSS, NO2, NO3, NH4, TN, TP, PO4 and turbidity. Oxygen measurements were also conducted in the stream and different sections of the wetland during   the evening hours (18:00), at night 22:00and early morning (04:30).


Results and discussion:

As shown in graph 1, almost all water quality parameters are lower in the outlet than in the inlet, indicating that processes within the wetland resulted in this apparent reduction of pollutants. BOD and TSS levels in the output were lower than <2 mg O2/l and  <8 mg/l, respectively. All nitrogen species (NO2, NO3, NH4) were lower than <1 mg/l in the output and TN had a value of a little over 1 mg/l. results relating to TP and PO4 in output were not as low having values of 2.79 mg/l and 8.83 mg/l respectively.


Graph 2, displays the percentage removal for these water quality parameters. As indicated by the graph, very high percentages of removal (>90%) is seen for the parameters of NO3, NH4, NO2, TSS, TN and turbidity. High percentage of removal is also seen for organic load parameters of BOD and COD with a removal of 85% and 73%, accordingly. A removal of only 45% is seen for TP and almost no removal or even negative removal is seen for PO4.   


Similar results have been found in other wetland pilot studies established in Israel. For example, Ran et al, 2004 found that their system had high treatment efficiency, with a high removal of TSS and organic parameters and a very low almost negligible removal for Phosphorous. Moreover, Green et al, experienced high removal of  suspended solids and organic load in their system while the phosphorous removal levels changed from more than 90% to zero and even negative removal. The decrease in Phosphorous removal is explained by the fact that most Phosphorous removal is governed by sorption processes on the media used, and once this sorption capacity is saturated this processes no longer takes place (Green M, 1996).

Graph 3 illustrates the different pollution concentrations in the inlet, the sedimentation pool, the center of the SSF system and the outlet. The objective of this graph is to show the relative contribution of each system component to the purification of the water. As this graph reveals, for most water quality parameters there is a reduction between the different colored steps in the graph, meaning that each system component contributes to the reduction in pollutant concentration.


Graph 4 displays the measured oxygen concentration in the wetland system. These results show that oxygen concentration is very low inside the wetland system (<0.5 mg/l). High oxygen concentrations are seen in the stream at evening and night, with lower concentration in early morning. Higher oxygen concentration was measured in the wetland outlet (4.4-6.5 mg/l), however these oxygen levels are attributed to the waterfall created by the drop in water level as the water from the hose reaches ground level. These results show that in fact, the wetland system is suboxic(low-oxygen levels) with all processes taking place under conditions of constant low concentrations. Very high oxygen concentrations (above saturation) of oxygen in the stream during the day and low oxygen levels during early morning suggest that the stream faces eutrophic conditions.


Comparison between water quality after wetland treatment and Inbar water quality standards


Inbar standards for rivers

Wetland outlet

Compliance of wetland quality with Inbar standard

COD (mgO2/l)




BOD (mgO2/l)




TSS (mg/l)




NH4 (mg/l)




TN (mg/l)




TP (mg/l)




Table 1: Selected water quality parameters from the Proposed Inbar standards and their comparison to water quality parameters in the output of the wetland          system.


The results of the water quality parameters examined for this wetland, indicate that constructed wetlands of this kind can be used as an efficient means to improve the Alexander stream water quality, and comply with most requirements set forward by the Inbar water quality standards for discharge into rivers. Nevertheless, Phosphorus requirements are not complied with, suggesting that different measures should be taken for the compliance with Phosphorus standards. Conclusions from other wetland pilot studies (Green 1996, Ran 2004) strengthen the claim that wetlands are an efficient mean for water quality improvement and could comply with Israeli standards for river discharge, especially for suspended solids and organic matter removal.   


Moreover, the establishment of such wetland system have been indicated as one of the possible alternatives for improving water quality in the Alexander stream(Juanico M and Friedler E, 1995). Gafny argued that the integration of wetlands is the most essential component of the stream restoration project(Gafny A, 1995)In fact, a plan for a wetland project in the Alexander watershed is planned in the near future. This wetland system will be based upon the pilot study established in the Alexander watershed in 1995 (Green M, 1996). The planned wetland system will be conducted on a small scale treating an amount of approximately 60 cm3/day.  This wetland will consist of two hundred meters pool units and will treat the water discharging from the emergency WWTP in Yad-Hanna that treats the wastewater of Nablus and Tul-karem (Almon, personal communication, 8.6.06). Nowadays, about six thousands CM are discharged into the stream from the Yad-Hanna treatment plant, (treats the wastewater coming both from Nablus and Tul-Karem). In order to treat this amount of water, a larger wetland system with an area of about forty to sixty Dunham will be required to bring the water quality to tertiary level. (Cohen, personal communication, 25.7.06)


Since reclaimed water seems to currently be the most available source for restoring Israeli streams that have gone dry, some policy makers have adopted this notion, arguing that it offers realistic solution both for stream restoration and for efficient to   removal of contaminants from waste water effluents.  (Juanico M and Friedler E, 1999; 2004).


Under current water availability conditions, streams will continue to receive effluents from WWTP. Under these conditions, if effluent quality fails to meet water quality standards, than river system are not likely to improve in the near future. Although the Nature and Parks Authority (2004) excess wastewater in the area might be still discharged into the stream.

Thus, it is obvious that if reclaimed wastewater will provide water for streams undergoing restoration, than the water quality discharged from treatment plants should improve. This improvement can be accomplished either through conventional treatment or using wetland systems.


Wetland systems present some advantages in comparison with conventional treatment systems. In conventional treatment systems, nonrenewable fossil-fuel energy provides the source of energy, where in wetland system the energy source is renewable, mainly solar energy. Moreover, many conventional treating processes, result in the formation of residues or sludge, which present a disposal problem, one that those not exist in the wetland system. Wetland systems require low maintenance efforts, resulting in lower operation and maintenance costs compared to conventional systems {Kadlec R.H. and Knight R.L. 1996 #1340} 


Thus, given the water quality improvement demonstrated by wetland systems, such systems might serve as an effective and environmental friendly solution for water quality improvement before discharge of effluents into Mediterranean streams





















                                                                   Graph 1: water quality parameters in inlet and outlet of wetland system           













Graph 2: % removal of water quality parameters in wetland                                                                                        















graph 3: Illustration of relative contribution of pollutant reduction in selected parts of the wetland system.                             






































 Graph 4: Oxygen levels measured in different locations in wetland systems at 18:00, 21:00 and 04:30 in 27-28/6/20                                       






















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