ANALISIS MACROECONOMICO

The experiment was performed in a 500 m²greenhouse built 60 m down-stream of Abu-Nusier wastewater treatment plant located north of Amman. Half of the greenhouse was utilized for growing tomato with the following three water treatments:

1. Effluent of the existing activated-sludge treatment plant before chlo-rination

2. Effluent of a pilot anaerobic-aerobic system consisting of a com-bined Upflow Anaerobic Sludge Blanket (UASB) reactor followed by Rotating Biological Contactors (RBC)

3. Fresh water as a control

The pressurized irrigation system consisted of a pressure regulator at the inlet, a disc filter, sand filter, and a fertilizer injection unit at the storage tanks. A main line from each storage tank carried water to the

green-Sustainable Management of Wastewater for Agriculture

house. Every plot in the greenhouse contained two laterals from a main line. Every lateral contained five drippers supplying 4.3 L h^-1. The field was ploughed twice before the experiment. The planting area was divided into blocks separated by paths 0.5 m wide. Water treatment plots were ran-domly distributed. The irrigated area was covered with mulch to prevent direct contact between irrigation water and plants.

Soil samples were collected both 5 and 10 d after the last irrigation.

Samples were taken at four depths: 0-15, 15-30, 30-45, and 45-60 cm.

Water samples were collected before each irrigation, while leaves and fruits of tomato plants were collected at the end of the experiment. Plant and soil samples were transferred directly to the laboratory for analysis.

Wastewater samples were collected using sterile bottles containing sodium thiosulfate and the samples transferred directly to the laboratory for analy-sis. Total coliforms, E. coli, Enterococcus, and Salmonella were analyzed in all samples. A certain weight of sample (soil or macerated plant) was dilut-ed to 100 mL using 0.85% NaCl as describdilut-ed by Poxton et al., (1989).

Pathogens were then measured following the enzyme substrate test (APHA 1995). Wastewater sample determinations followed APHA (1995).

3 Results and discussion

The measured average total coliforms, E. coli, and Enterococcus in water used in treatments are shown in Table 1. No Salmonella was detected in any water samples. The values of biological indicators on tomato fruit, leaves, and in soils are shown in Tables 2 and 3, respectively. It is notewor-thy that fruit in all cases (except one) had < 1 MPN g^-1dry plant of each biological indicator, although wastewater (Table 1) contained high patho-genic loads. According to WHO (1989), wastewater with qualities reported in Table 1 should not be used for unrestricted irrigation to prevent associat-ed health risks. However, this study shows that when irrigation techniques and agricultural practices are taken into account, health risks are mini-mized at lower treatment costs. The present results were better than those of Manios et al. (2005) who concluded that there was pathogenic con-tamination on the surface of tomato and cucumber from indirect move-ment of pathogens by insects in the greenhouse. The mulch cover mini-mized contact between plants and wastewater. However, one measure-ment of total coliforms was 72 MPN g^-1dry plant and one measurement for Enterococcus was 21 MPN g^-1dry plant. According to WHO (2006) guide-lines, washing produce would reduce pathogens by one log unit, which means that washing tomatoes would guarantee a safe product.

Pathogens in Plants and Soil Irrigated with Secondary Treated Wastewater

Table 1 Biological indicators measured for three water treatments

Parameter (MPN/100 mL) 10⁵x WWTP UASB-RBC x10⁵ Freshwater

Total coliforms 4.8 68.69 <1

E. coli 1.5 31.77 <1

Enterococcus 0.02 0.008 Not detected

Table 2 Biological indicators in tomato (leaves and fruit) for three water treat-ments

Parameter (MPN/g dry plant) Freshwater WWTP UASB-RBC

Total coliforms Leaves <1 <1 <1

Fruits <1 <1(71.57) <1

E. coli Leaves <1 <1 <1

Fruits <1 <1 <1

Enterococcus Leaves <1 <1(24.29) <1(2.3x10³)

Fruits <1 <1 <1(20.45)

* One sample had higher values, as given in prarentheses

Table 3 Biological indicator concentrations in soil samples taken at different depths for three water treatments

5 days after the last irrigation 10 days after last irrigation Total coliforms (MPN g^-1dry soil) Total coliforms (MPN g^-1dry soil) Depth Freshwater WWTP UASB-RBC Freshwater WWTP UASB-RBC

0-15 339 8.95 70.45 15.48 19.23 <1

15-30 1.19×10³ 4.36 19.60 <1 <1 <1

30-45 5.67 1.98 199.00 <1 2.74 <1

45-60 38.90 133 33.38 <1 3.82 <1

E. coli (MPN g^-1soil) E. coli (MPN g^-1soil)

0-15 <1 1.499 24.08 <1 <1 <1

15-30 3.13 1.195 6.92 <1 <1 <1

30-45 <1 <1 <1 <1 <1 <1

45-60 6.69 <1 2.74 <1 <1 <1

Enterococcus (MPN g^-1soil) Enterococcus (MPN g^-1soil)

0-15 1.28×10³ 96.74 891 22.39 14.93 8.79

15-30 513 42.53 715 14.43 13.44 23.36

30-45 57.98 40.04 36.5 1.17 20.02 7.24

45-60 22.96 43.11 1.31x10³ 0 7.04 8.11

WWTP = Effluent of the existing activated sludge treatment plant before chlorination;

UASB-RBC = Effluent of a pilot anaerobic-aerobic system consisting of a combined Upflow Anaerobic Sludge Blanket, UASB, reactor followed by Rotating Biological Contactors, RBC

Sustainable Management of Wastewater for Agriculture

Indicator pathogen counts in different soil layers for all treatments are shown in Table 3. Compared with total coliform values in freshwater (Table 1), the counts measured in soil 5 d after the last irrigation (Table 3) showed that soil was not free of this indicator pathogen. Rufete et al. (2006) meas-ured a total coliform count in soil without additional treatment of around 104 colony forming units/g dry soil, which indicates that soils may have sig-nificant background of total coliforms. Regrowth of indicator pathogens in soil was reported by Gibbs et al. (1997) and high humidity was among the factors that helped growth of enteric bacteria (Entry et al. 2000, Rufete et al. 2006). The total coliform count decreased with time and soil dryness as shown 10 d after irrigation ceased (Table 3).

The E. coli did not survive in soil after irrigation; the E. coli count decreased considerably from maximum values of 24 MPN g^-1dry soil when irrigation was with UASB-RBC effluent (Table 3). Ten days after irrigation ceased, the E. coli count was < 1 MPN g^-1dry soil in all analyzed soil samples. Short sur-vival times for E. coli were previously reported, e.g. Entry et al. (2005) did not detect E. coli in any soil sample after 1 d of application to soil. With respect to Enterococcus, there was a 2-3 log unit reduction in soil samples taken at all depths 5 d after the last irrigation, compared with counts in irri-gation wastewater. Although Enterococcus was counted after the 10-day period following the last irrigation in all soil layers (except one), there was a considerable reduction in their concentration compared to soil samples 5 and 10 d after the last irrigation. Survival of these pathogens in soil layers is expected to decrease with time.

4 Discussion

A preliminary model was established to assess risk of infection and disease associated with wastewater irrigation of vegetables eaten uncooked (Shuval et al. 1997). This showed that irrigating with wastewater effluent, which met WHO (1989) guidelines with respect to fecal coliforms, would provide a safety factor of 1-2 orders of magnitude greater than that used by the US Environmental Protection Agency for acceptable microbial stan-dards for drinking water. Indeed public health protection is a major con-cern; however, wastewater is a resource that should be fully exploited and irrational standards will limit its use. Moreover, protection of public health cannot be achieved solely at the treatment plant as pathogen regrowth does occur (Gantzer et al. 2001). Instead, health protection can be

achieved using 'multiple barriers' (Carr et al. 2004) that interrupt the flow of pathogens to humans. In this approach, soil, wastewater treatment, irriga-tion technique, and human exposure control are all important in determin-ing the fate of pathogens in wastewater. At the same time, the cost of wastewater treatment is reduced as soil and crops serve as biofilters

5 Conclusions

Pathogenic indicators measured on tomato plants and in soil irrigated with treated wastewater from an extended aeration treatment plant and an integrated UASB-RBC pilot plant showed that total coliforms and

Enterococcus counts on nearly all tomato fruit samples and E. coli count on all fruit samples were < 1 MPN g^-1dry splant. Although secondary treat-ed wastewater had indicator pathogenic counts of 2-5 log units, there was a considerable reduction in soil samples collected 5 and 10 d after the last irrigation. By 10 d after the last irrigation, all soil samples collected from all depths had < 1 MPN g^-1dry soil of E. coli, while total coliform counts ranged from less than 1 MPN to 19.23 MPN g^-1dry soil. With respect to the measured indicator pathogens, the results suggest that disinfection of reclaimed wastewater may not be necessary when proper agricultural practices are applied downstream of the treatment plant.

Acknowledgments

This research was part of the activities carried out on a CORETECH-EU ENCOMED funded project.

References

APHA. 1995. Standard Methods for the Examination of Water and Wastewater. 19th edition, American Public Health Association, Washington, DC.

Carr, R., U. Blumenthal and D. Mara. 2004. Guidelines for the safe use of waste-water in agriculture: revisiting WHO guidelines. Water Science and Technology 50: 31-38.

Entry, J., R. Hubbard, J. Thies and J. Furhmann. 2000. The influence of vegetation in riparian filterstrips on coliform bacteria I. Movement and survival in surface flow and groundwater. Journal of Environmental Quality 29: 1206-1214.

Entry, J., A. Leytem and S. Verwey. 2005. Influence of solid dairy manure and com-post with and without alum on survival of indicator bacteria in soil and on potato. Environmental Pollution 138: 212-218.

Gantzer, C., L. Gillerman, M. Kuznetsov and G. Oron. 2001. Adsorption and survival of faecal coliforms, somatic coliphages and F-specific RNA phages in soil irrigat-ed with wastewater. Water Science and Technology 43: 117-124.

Gibbs, R., C. Hu, G. Ho and I. Unkovich. 1997. Regrowth of fecal coliform and sal-monellae in stored biosolids and soil amended with biosolids. Water Science and Technology 35: 269-275.

Haruvy, N. 1997. Agricultural reuse of wastewater: nation-wide cost-benefit analysis.

Agriculture Ecosystems and Environment 66: 113-119.

Manios, T., I. Papagrigoriou, G. Daskalakis and I. Sampathianakis. 2005. Evaluation of primary and secondary treated and disinfected wastewater irrigation of tomato and cucumber plants under greenhouse conditions, regarding growth and safety considerations. Proceedings of the First International Pathogens in Plants and Soil Irrigated with Secondary Treated Wastewater

Conference on Sustainable Urban Wastewater Treatment and Reuse.

Organized by the National Technical University of Athens, University of Cyprus and Agricultural Research Institute of Cyprus. September 15-16. Nicosia, Cyprus.

Poxton, I.R., Brown, R. and Wilkinson, J.F. 1989. pH measurements and buffers, oxida-tion-reduction potentials, suspension fluids and preparation of glassware. In:

Practical Medical Microbiology. Ed. Collee, J.G., Duguid, J.P., Fraser, A.G.

and Marmion, B.P. Thirteenth Edition. Longman Group, UK.

Rufete, B., M. Perez-Murcia, A. Perez-Espinosa, R. Moral, J. Moreno-Caselles and C.

Paredes. 2006. Total and fecal coliform bacteria persistent in a pig slurry amended soil. Livestock Science 102: 211-215.

San'a Declaration. 2006. Sana'a statements on wastewater use in agriculture.

Expert group meeting on 'municipal wastewater use for irrigation'. Water environment centre - Sana'a, Yemen, 4-7 November 2006.

Shuval, H., Y. Lampert and B. Fattal. 1997. Development of risk assessment

approach for evaluating wastewater reuse standards for agriculture. Water Science and Technology 35: 15-20.

WHO. 1989. Health guidelines for the use of wastewater in agriculture and aquacul-ture. Technical Report Series 778. World Health Organization, Geneva.

WHO. 2006. WHO guidelines for the safe use of wastewater, excreta and greywa-ter. Volume II: wastewater use in agriculture. World Health Organization, Geneva. Switzerland. ISBN 92 4 154683 2 (v.2).

Sustainable Management of Wastewater for Agriculture

Effect of Wastewater Application on Parsley