Wastewater Reuse Applications in Turkey

Although the Turkish legislation on wastewater reuse in agriculture has already been established in 1991, there is no major improvement in its application since that time. In Turkey, only few wastewater reuse applications exist in small communities, where wastewater of domestic nature is used for irrigation of forest areas, gardens and parks [16]. Besides, there are several nationwide medium-to-large scale project activities planned for the treatment of urban wastewater and its reuse for agricultural irrigation purposes [17]. For instance, treated effluent originating from Ankara Metropolitan Sewage Treatment Works is used for irrigation of several crops. Currently there are planning efforts in Konya province, which is particularly known as the "grain cellar" and is the largest agricultural area of the country, to use secondary (biologically) treated urban wastewater for the irrigation of cereals. A comprehensive, regional project known as the Southern Anatolia Project (in Turkish: Guneydogu Anadolu Projesi, abbreviated as GAP) also features wastewater treatment and reuse for agricultural irrigation purposes. Another example for the few case studies on urban wastewater reuse in Turkey is the irrigation of edible and other type of crops with secondary treated domestic effluent originating from the Metropolitan Gaziantep Sewage Treatment Plant, with a total wastewater volume of 73 Mm3/year [18].

On the other hand, it has been reported that the indirect use of domestic waste-water as irrigation water is eventually illegally practiced in Turkey. The above mentioned and recently completed MEDA-Water project demonstrated that in most cases the quality of even secondary treated urban wastewaters sampled from different Turkish urban wastewater treatment plants is not suitable for agricultural use, mainly because these effluents do not meet most of the irrigation water quality criteria, such as total Coliform, sodium absorption ratio (SAR), conductivity, and salinity values given by the National Water Pollution Control Regulation Technical Aspects Bulletin shown in Table 31.2 [19].

Table 31.2 Turkish water quality criteria for irrigation [19]

Quality classes of irrigation water

Table 31.2 Turkish water quality criteria for irrigation [19]

Quality classes of irrigation water

Class I

Class II

Class III

Class IV (Usable

Class V

Quality criteria

(Perfect)

(Satisfactory)

(Usable)

with care)

(Harmful)

EC25

0-250

250-750

750-2,000

2,000-3,000

>3,000

(mmhos/cm) x 106

Sodium (%)

<20

20-40

40-60

60-80

>80

SARa

<10

10-18

18-26

>26

SCRb (meq/L or

>1.25

1.25-2.5

>2.5

mg/L)

<66

66-1(3

>1((

Cl- (meq/L or

0-4

4-7

7-12

12-20

>20

mg/L)

0-142

142-249

249-426

426-710

>710

SO42- (meq/L or

0-4

4-7

7-12

12-20

>20

Mg/L)

0-192

192-3(6

((6-575

575-960

>960

TDS (mg/L)

0-175

175-525

525-1,400

1,400-2,100

>2,100

Boron (mg/L)

0-0.5

0.5-1.12

1.12-2.0

>2.0

-

Class of irrigation

C1S1d

C1S2> C2S2>

C1S(, C2S(,

C1S4, C2S4,

-

waterc

C2S1

C(S(, C(S2, C(S1

C4S1

NO3- N or NH4+-N

0-5

5-10

10-(0

30-50

>50

(mg/L)

Fecal coliforms

0-2

2-20

20-100

100-1,000

>1,000

(100 CFU/mL)

BOD5 (mg/L)

0-25

25-50

50-100

100-200

>200

TSS (mg/L)

20

(0

45

60

>100

PH

6.5-8.5

6.5-8.5

6.5-8.5

6.5-9

<6 or >9

aSodium adsorption ratio bSodium carbonate residue cDepends on the plant type dC = Conductivity; S = SAR

n J ' n aSodium adsorption ratio bSodium carbonate residue cDepends on the plant type dC = Conductivity; S = SAR

This issue can also be due to the fact that some of the Turkish urban wastewater treatment plants regularly receive brackish water (seawater), or industrial wastewater (for instance textile industry wastewater). Eventually these factories don't have disinfection units or these units are not maintained and/or operated properly, namely as consequence of high electrical energy consumption and/or costs of disinfecting chemicals. Surprisingly, boron (another significant water quality parameter indicated in the national irrigation standards) generally doesn't reach significant levels in the effluents of sewage treatment plants and hence it doesn't create any serious environmental problem if reuse for agricultural irrigation is envisioned.

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