Sarikaya, H.Z., Akça, L., Yazgan, M. ve C.Özdemir, “Konya Endüstriyel Atık Sularının Sulama Için Yeniden Kullanımının Değerlendirilmesi”,Proceedings of 1st International Workshop on Environmental Quality and Environmental Engineering in the Middle East Region, 438 - 450, Konya, 1998.
EVALUATION OF THE IRRIGATIONAL REUSE OPTION OF THE EFFLUENTS OF KONYA CITY
H. Sarıkaya*, L. Akça*, M.S. Yazgan*, C. Özdemir**
*Environmental Engineering Department, İTÜ, İstanbul, Türkiye
**Environmental Engineering Department, Selçuk University, Konya, Türkiye
SUMMARY
In this study, irrigational reuse option of wastewater from Konya city which has been discharging into Tuz Lake without any treatment was evaluated. Local, international and national irrigational reuse standards were summarized. Konya city is an important grain producer of Turkiye and has semi-arid climate. The water for irrigation of agricultural fields is not adequate. Thus effluent from Konya which meets the most irrigational reuse standards after secondary treatment could be used for irrigation of grain and also sugar beet crops. This option will be both economical and ecological solution to the wastewater disposal problem of Konya city.
KEYWORDS: Wastewater disposal, reuse, irrigational use, irrigation standards, Konya,
INTRODUCTION
The city of Konya is situated in the middle of Anatolia whose grain production is the richest as far as Turkiye is concerned. Thus, Konya is also named as the grain silo of Türkiye. On the other hand Konya’s climate is semi-arid and irrigation of the farmlands is usually not adequate. Consequently, supplement of the existing water resources with treated wastewater needs to be evaluated as a viable option due to following reasons and benefits :
- Currently, the untreated wastewater is flowing into Tuz Lake and causing environmental and health problems. Advanced wastewater treatment including nutrient removal will be needed to control the pollution. Even this option will not completely terminate the pollution since discharge of effluents will continue. Furthermore, the advanced treatment is a very expensive alternative for wastewater management when concerning Türkiye’s economical conditions. On the other hand reuse of the effluents will restore the lake to its original status due to no discharge of effluents
- Reuse of the treated effluent reduces the pressure on the fresh water resources. Fresh waters substituted with the reclaimed wastewater may be allocated to the other uses which require better quality
- Required degree of wastewater treatment for irrigational reuse may be less than the one needed for the discharge of effluents into the Tuz Lake. For instance removal of the nutrients such as N and P are required for discharge into the Lake, whereas these elements are benefical for irrigational reuse and they need not to be removed at the reclamation plant. Thus, cost of treatment for reuse can be lower than the cost of treatment for discharge into the Lake. In addition to this, nutrients in reclaimed wastewater have fertilizer value.
Considering the benefits of the irrigational reuse of the effluents from the future wastewater treatment plant of Konya city, the aim of this paper has been formulated as to overview the issue and highlights the elements of the option to be elaborated by the further studies.
WATER QUALITY CRITERIA FOR IRRIGATIONAL REUSE AND TREATMENT REQUIREMENTS
Water quality criteria has been well established for irrigational reuse of reclaimed wastewater. Required water quality depends on the ;
- Type of the crop
- Method of the irrigation.
The crops eaten at row stage and the irrigated with sprinkler system require the most stringent standards and water quality. If there is no any restriction either on the type of crop or on the method of irrigation, this is called “unrestricted irrigation”. The “restricted irrigation” is the term applied for the cases where there are restrictions on the crop type and the method of irrigation.
Local, international and some national water quality criteria and standards for irrigational reuse are summarized below:
Local Standards
Issue of the water quality standards were delayed up to January 7, 1991 though reuse applications had been started much earlier. Turkish Ministry of Environment has published the “Irrigational Reuse Standards” under “Technical Procedures Decree” in Official Gazette on January 7, 1991.
The Classification of the irrigation waters in accordance with the above mentioned local standards is presented in Table:1 and technical limitations based on the crop type are given in Table:2
Turkish Regulations do permit the reuse of the effluents of biological treatment to irrigate farms and grass lands. On the other hand disinfection required for the effluents of the waste stabilization ponds. This is in contrast with other standards, since it is a well known fact that the waste stabilization pond effluents are bacteriologically safer than the conventional secondary treatment effluents.
Although the recent developments have not been included in Turkish irrigational reuse standards, they filled a gap in this field in spite of the several deficiencies in terms of the quality parameters and their limit values.
Table: 1. Irrigation water quality criteria for classification of the irrigation waters
Quality Criteria / 1st class(Very good) / 2nd class
(Good) / 3rd class
(May be use) / 4th class
(Use with care) / 5th class (Hazardous)
pH / 6.50-8.50 / 6.50-8.50 / 6.50-8.50 / 6.00-9.00 / <6.00, 9.00>
ECx106 (µmhos/cm) / 0-250 / 250-750 / 750-2000 / 2000-3000 / >3000
Tot.Salinity (mg/l) / <175 / 175-525 / 525-1400 / 1400-2100 / >2100
Temperature (0C) / 30 / 30 / 35 / 40 / >40
SO4 (me/l) / 0-4 / 4-7 / 7-12 / 12-20 / >20
Cl- (me/l) / 0-4 / 4-7 / 7-12 / 12-20 / >20
B (mg/l) / 0.050 / 0.50-1.12 / 1.12-2.00 / 2.00 / -
% Na / <20 / 20-40 / 40-60 / 60-80 / >80
SAR / <10 / 10-18 / 18-26 / 26 / -
RSC (me/l) / <1.25 / 1.25-2.50 / 2.50 / - / -
Fecal Coliform (1/100 ml) / 0-2 / 2-20 / 20-102 / 102-103 / >103
BOD5 (mg/l) / 0-25 / 25-50 / 50-100 / 100-200 / >200
SS (mg/l) / 20 / 30 / 45 / 60 / >100
NO3 or NH4 (mg/l) / 0-5 / 5-10 / 10-30 / 30-50 / >50
Irrigation water class / C1S1 / C1S2-C2S2
C2S1 / C1S3-C2S3
C3S1- C3S3
C3S2 / C1S4-C2S4
C3S4-C4S3
C4S2-C4S4 / -
Table: 2. Technical limitations based on the crop type
Type of Agriculture / Technical RestrictionsOrchards and Vineyards /
- Spray irrigation is forbidden
- No fruits picked from ground should be eaten
- Number of fecal coliform must be 1000/100 ml
Fibrous Crops and Seed Production /
- Surfaceand spray irrigation is possible
- Biologically treated and disinfected wastewater can be used in sprinkler irrigation
- Number of fecal coliform must be 1000/100 ml
Feed Crops, Oil Crops, Floriculture and Crops not eaten raw /
- Surface irrigation, Mechanically treated wastewater
World Health Organization (WHO) Standards:
The recommended microbiological quality guidelines for reclaimed water used for agricultural and urban irrigation are summarized in Table: 4. The guidelines are based on the conclusion that the main health risks in developing countries are associated with helminth diseases and therefore, a high degree of helminth removal is necessary for the safe use of wastewater in agriculture.
Table: 4. Recommended microbiological quality guidelines for wastewater use in agriculturea
Category / Reuse Conditions / Exposed Group / Intestinal nematodesb (arithmetic mean no. Of eggs per literc) / Fecal Coliforms (Geometric mean no. Per 100 mlc) / Wastewater treatment expected to achieve the required microbiological qualityA / Irrigation of crops likely to be eaten uncooked, sports fields, public parksd / Workers, consumers, public / 1 / 1000d / A series of stabilization ponds designed to achieve the microbiological quality indicated or equivalent treatment
B / Irrigation of cereal crops, industrial crops, fodder crops, pasture and treese / Workers / 1 / No standard recommended / Retention in stabilization ponds for 8-10 days or equivalent helminth and fecal coliform removal
C / Localized irrigation of crops in category B if exposure of workers and the public does not occur / None / Not applicable / Not applicable / Pretreatment as required by the irrigation technology, but not less than primary sedimentation
a In specific cases, local epidemiological, sociocultural and environmental factors should be taken into account and the guidelines modified accordingly
bAscaris and Trichuris species and hookwarm
c During the irrigation period
d A more stringent guideline (<200 fecal coliforms per 100 ml) is appropriate for public lawns, such as hotel lawns whit which the public may come into direct contact.
e In the case of fruit trees, irrigation should cease two weeks before fruit is picked and no fruit should be picked off the ground. Sprinkler irrigation should not be used
While the guidelines do not specifically refer to all helminths of public health significance, the intestinal nematodes covered are intended to serve as indicator organisms for all of the large settleable pathogens (1).
National Standards :
While some countries follow the standards given by WHO, many countries have their own reuse standards though they share same quality parameters. Reuse standards and requirements are either on water quality or on the treatment level or both.
Here in this section only the standards of USA (California) and Israel will briefly given. In USA the standards are varying from state to state. Among them California has the greatest experience of reuse. Therefore, only the Californian Standards will be presented as an example.
USA (California)
The state of California has a long history of reuse and developed the first reuse regulations in 1918, which have been modified and expanded through the years. The state’s current Wastewater Reclamation Criteria were adopted in 1978 and have served as the basis for reuse standards in other states and countries. The reclamation criteria include water quality standards, treatment processes requirements, operational requirements and the treatment reliability requirements (1). The treatment and quality criteria are shown in Table: 5.
Table: 5. California treatment and quality criteria for water reuse
Type of Use / Total Coliform Limits / Treatment RequiredFodder, Fiber and Seed Crops
Surface Irrigation of Orchards and Vineyards / - / Primary
Pasture for Milking Animals, Landscape Impoundments, Landscape Irrigation (Golf Courses, Cemeteries, etc.) / 23/100 ml / Oxidation &
Disinfection
Surface Irrigation of Food Cropsa, Restricted Recreational Impoundments / 2.2/100 ml / Oxidation &
Disinfection
Spray Irrigation of Food Cropsa, Landscape Irrigation (Parks, Playgrounds, etc.)
Nonrestricted Recreational Impoundments / 2.2/100 ml / Oxidation ,
Coagulation, Clarification,
Filtrationb
Disinfection
a Exceptions may be made to the requirements for processed food crops
b The turbidity of filtered effluent cannot exceed an average of 2 turbidity units during any 24-hour
Israel
Since most wastewater in Israel are being reused for agricultural irrigation, much thought has been invested in establishing the necessary quality requirements. Reuse standards of Israel established in 1978. Although there are many similarities between the Israeli requirements (Table: 6) and those issued by the State of California (1978), the former are more detailed in the various consumptive use within the agricultural sector and the health risk assumed for each group of crops (2).
Table: 6. Quality criteria of treated wastewater effluent to be reused for agricultural irrigation in Israel
Group of Crops / A / B / C / DPrincipal Crops / Cotton, sugar beet, cereals, dry fodder, seeds, forest irrigation / Green fodder, olives, peanuts, citrus, bananas, almonds, nuts, etc. / Deciduous fruits**, conserved vegetables, cooked and peeled vegetables, green belts, football fields and golf courses / Unrestricted crops, including vegetables eaten uncooked (raw), parks and lawns
Effluent Quality / (requirements should be met in at least 80% of samples taken)
BOD5, total, (mg/l)
BOD5, dissolved, (mg/l)
Suspended solids, (mg/l)
Dissolved oxygen, (mg/l)
Coliforms counts, (1/100 ml)
Residual avail. chlorine, (mg/l)
Mandatory Treatment
Sand filtration or equival.Chlorination, minimum
contact time, (min)
Distances
From residential areas, (m)From paved road, (m) / *60
--
*50
0.5
--
-
--
--
--
300
30 / *45
--
*40
0.5
--
-
--
--
--
250
25 / 35
20
30
0.5
250
-
0.15
--
60
--
-- / 15
10
15
0.5
12 (80%)
2.2 (50%)
0.5
required
120
--
--
* Different standards will be set for stabilization ponds with retention time of at least 15 days
** Irrigation must stop two weeks before fruit picking; no fruit should be picked from the ground
IRRIGATIONAL REUSE POTENTIAL FOR KONYA CITY
At the present, untreated wastewater of Konya city are being pumped into Tuz Lake which is about 150 km away. Domestic and industrial wastewater are first discharged into Keçili channel at the upstream and into State Hydraulic Works (DSİ) main drainage channel downstream to convey the wastewater to Tuz Lake. There is a pollution problem in Tuz Lake due to the wastewater discharges and central and local authorities are working on the solution of this problem.
Wastewater treatment plant of Konya city has been planned at 2 stages as the year 2000 and 2015 and the process calculations have been carried out using the input data given in Table : 7.
Planned wastewater treatment and disposal system of Konya city proposes the treatment of wastewater by activated sludge system and disposal of the effluent to Tuz Lake by existing drainage channels. However, in this case untreated constituents such as organic matter and nutrients cause pollution of the lake continuously even if their concentrations are at the lower levels. Moreover, due to unsuccesfull operational conditions and failure in treatment systems, there will be some risks on pollution of the lake. On the other hand, untreated wastewater in existing drainage channels are used as an irrigation water in summer season. This usage may continue after construction of planned treatment system. Thus, disinfection unit must be added to the planned system. Otherwise some water born diseases may appear in the areas near the fields irrigated by the undisinfected effluents.
Table: 7. Designdata of Konya wastewater treatment plants
Parameter / Stages IYear 2000 / Stages II
Year 2015
Equivalent Population
Total Organic Load (kg BOD5/day)
Daily Wastewater Flow (m3/day)
Average Flow (m3/sec)
Design Flow (m3/sec) / 1 019 500
61 170
298 598
3 456
4 367 / 1 572 366
94 342
475 632
5505
6529
Some wastewater quality parameters of Konya city are given in Table: 8.
Table: 8. Wastewater characteristics of Konya city (3)
Parameters / RangeBOD5 (mg/l) / 365-672
COD / 750-1020
Total solids (mg/l) / 475-1710
Volatile solids (mg/l) / 128-480
Total settleable solids (ml/l) / 4.5-21.5
Total suspended solids (mg/l) / 106-421
pH / 7.5-8.3
NO3 / 0.25-0.7
Temperature (0C) / 10.8-15.1
Oil-Grease (mg/l) / 196-284
Zn (g/l) / 87-130
Cu (g/l) / 2-17
Cd (g/l) / <1
Total Cr (g/l) / 10-69
Hg (g/l) / 0.5-2.4
Table: 8 includes the ranges of the parameters during the sampling period of January to June, 1997. As it can bu seen from the table, the wastewater parameters indicate strong municipal wastewater charactersitics.In the case of irrigational reuse of wastewater of Konya city, the objective of treatment will change from protection of water quality to providing irrigational reuse standards. Thus existing plans for wastewater treatment system must be reevaluated. Economical aspects, local conditions such as climate, topography etc. and other technical details such as storage facilities should also be taken into consideration.
The waste stabilization pond technology is proven reliable and cheap and is an appropriate technology for hot and temparate climates and for rural and urban populations. The large land area requirement of the ponds is frequently an overstated critism which requires careful evaluation before the application of pond technology. The waste stabilization pond alternatives are generally are discarded simply on the basis of land cost or availability. But it should be noted that, it is a wastewater reclamation and recovery technology rather than simply a sewage treatment process.
Any type of the pond systems (either aerobic, facultative or anaerobic) has the organic matter (BOD5) removal potential, as much as % 60-80 and pathogen removal capability as much as % 99 or even higher. Thus the waste stabilization pond technology might be a viable alternative for the Konya city, which requires the technical and economical evaluations.
The waste stabilization ponds or other treatment processes have the disadvantage that one can only use their effluent for irrigation during the irrigation season; at other times of the year it is, unless somehow stored, wasted usually by discharge to a receiving water. Storage is more sensible as it permits a much greater area of land to be irrigated during the irrigation season.
There are some natural reservoirs for the purpose of wastewater storage during out of irrigation season in vicinity of Konya city. One of them is Hotamış Lake which is nearest and much appropriate one for irrigation purposes. This lake which is a natural wetland and mostly covered by reed plants is declared as natural protection zone by Culture Ministry of Türkiye in 1992. The streams feeding the lake are faded and at present there is no water in the lake. Therefore, by storing the treated wastewater, both the lake gains its ecological functions again and the quality of effluent will improve. The literature data show that natural wetlands are cabaple of upto 80% of BOD5removal. If the influent BOD5 concentration of natural wetlands is about 50-60 mg/l, effluent BOD5 concentration decreases to nearly 10-15 mg/l (4). In other words, the effluent quality of 10 mg BOD5 / l could be obtained if inlet BOD loading is about 10 kg/ha.day (5).
For irrigation waters, total dissolved solids (TDS) or salinity and Sodium Adsorption Ratio (SAR) are important quality parameters. TDS is generally less than 500 mg/l. Therefore, no salinity hazard is expected for irrigational reuse. SAR value of drinking water of Konya city is calculated as 0.81 (6). There is an ampirical relationship between SAR value of drinking water and that of its wastewater (7).
SAR (Effluent of biological treatment + filtration) = SAR (Drinking water) X 2.6
So SAR value of effluent of Konya city can be calculated as 2.11. Thus no SAR problem is expected. But comprehensive characterization study must be undertaken to reach a reliable evaluation of the wastewater quality.
Water Demand for Irrigation
Grain and sugar beet are the most important crops in Konya city. Irrigation water demand of these crops was calculated by Blaney-Criddle method which is a popular method to calculate the amount of irrigation water applied for agricultural fields. According to the parameters of monthly temperature, lightening ratio, water demand of crop, precipitation and evaporation ratio, calculated irrigation water demands of grain and sugar beet are given in Table: 9 and amount of irrigable area by Konya’s wastewater are given in Table: 10.
It is clear that, with storage of the wastewater out of the irrigational season, much larger area could be irrigated. The most stringent conditions for the storage rezervoir volume are obtained when all of the wastewater are used for crop irrigation. Following the irrigation schedule given in Table: 9, a storage volume of 76% of annual wastewater is calculated for use all wastewater for grain irrigation.
Table: 9. Calculated irrigation water demands of grain
and sugar beet fields in Konya
Water Demand (m3/ha)Months / Grain fields / Sugar Beet fields
April
May
June
July
August / 537
1469
151
-
- / -
346
1947
3080
1644
TOTAL / 2157 / 7017
Table:10. Amount of irrigable area by Konya’s wastewater
Irrigable area (ha)Storage / Irrigated crop / Year 2000 / Year 2015
No / Grain
Sugar beet / 6 096
2 908 / 9 710
4 632
Yes / Grain
Sugar beet / 50 520
15 530 / 80 473
24 739
Therefore, a storage volumes of 83 million m3 for the year of 2000 and 130 million m3 for the year of 2015 will be enough for irrigation of grain crops. Probable leaching, overflow, evaporation etc. will reduce the storage volume. Hotamış Lake having surface area of 226 000 000 m2 and nearly 300 million m3 estimated storage volume can be an appropriate alternative for storage as well as advanced natural treatment medium.