Wastewater Reuse for Irrigation : an Acceptable Soil Conditioner? Nicholas Kathijotes Department of Civil Engineering Higher Technical Institute Nicosia-Cyprus [e-mail]

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Wastewater Reuse for Irrigation an Acceptable
Soil Conditioner?Nicholas KathijotesDepartment
of Civil EngineeringHigher Technical
InstituteNicosia-Cyprusnkathijotes_at_hti.ac.cy
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Abstract

• Drought climatic conditions occurring around the
  Mediterranean region and the Balkans, suggest
  serious consideration as to the reuse of treated
  effluents resulting from treatment of domestic
  effluents. Taking into account that about 70 of
  the total water resources are used for
  agricultural purposes and mainly irrigation, then
  a tremendous conservation of hydrological
  resources can occur. Using however
  non-conventional quality water for irrigation,
  presents a number of ecological and health risks
  and poses problems connected with soil and ground
  water contamination. This paper concentrates in
  the general evaluation of the effects of these
  effluents on soils, and investigates and
  evaluates their effects in terms of organic
  matter enrichment and soil conditioning

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TREATED SEWAGE. Electrical Conductivity in dSm-1
and soluble cations-anions of water meq/l.
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CHARACTERISTICS OF GROUND FARM-WATER USED

• The following were the major characteristics of
  the ground water used
• high content of soluble elements toxic to
  agriculture
• electric conductivity 3.0 mmho/cm
• from the cations predominant is Na 21.7 mg/l
• from the anions predominant is Cl 15.5 mg/l
• It should be noted that Na2CO3 is one of most
  toxic to crops

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Soil profile evaluation, (SAR).
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SALTS EVALUATION

• A typical example in the presentation of the
  results as shown in the previous slide, SAR
  (sodium absorption ratio) is investigated by the
  application of various salts evaluation criteria
  at each increment of the soil profile under
  investigation. One may notice that the quality of
  the samples irrigated with groundwater obtained
  from nearby wells demonstrates higher values of
  SAR and therefore poses greater salinisation
  risk. This is due to the fact that most ground
  waters in Cyprus, due to their high content of
  calcium carbonate in the soils , present high
  level of salts.
• Soils of electrical conductivity below 4 dS/m and
  high values of SAR, between 13 and 15,are
  considered as sodic soils. These soils also
  demonstrate high pH values, usually above 10, and
  present various agricultural problems ,which are
  however manageable if proper care is given. Next
  slide shows the pH evaluation of our profile.

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pH Evaluationof Soil Profile

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Organic Content Evaluation on Profile
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CONCLUSIONS

• It is clear that ingredients contained in treated
  wastewater may create undesirable effects on
  soils and groundwater. However, careful
  management may overcome these effects. Soils in
  Cyprus are generally of low organic content. It
  is evident that by using treated wastewater for
  irrigation, besides the great savings in
  hydrological resources, the organic content of
  soils increases by about an average value of 21
  of the soil profile. Due to this increase of
  organic matter soils demonstrate structural
  improvement and consequently improvement of soil
  fertility. Structural improvement improves soils
  mechanically, and as a result the resistance to
  erosion is increased. This may be of greater
  interest in the restoration of disturbed land.
  Most of the humus that originates from treated
  sewage irrigation is gathered at the first 60cm
  of the profile and consequently around the plant
  root zone, which is highly beneficial to plants.
• It is however suggested that all factors should
  be well considered before planning a wastewater
  reuse network.

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• THANK YOU FOR YOUR ATTENTION