Removal of bacterial contaminants and antibiotic resistance genes by conventional wastewater treatment processes in Saudi Arabia: Is the treated wastewater safe to reuse for agricultural irrigation?

Abstract

Please cite this article as: Al-Jassim, N., Ansari, M.I., Harb, M., Hong, P.-Y., Removal of bacterial contaminants and antibiotic resistance genes by conventional wastewater treatment processes in Saudi Arabia: Is the treated wastewater safe to reuse for agricultural irrigation?, Water Research (2015Research ( ), doi: 10.1016Research ( /j.watres.2015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Abstract 1This study aims to assess the removal efficiency of microbial contaminants in a local wastewater 2 treatment plant over the duration of one year, and to assess the microbial risk associated with 3 reusing treated wastewater in agricultural irrigation. The treatment process achieved 3.9 logs 4 removal of heterotrophic bacteria and up to 3.9 logs removal of fecal coliforms. The final 5 chlorinated effluent had 1.8 x 10 2 MPN/100 mL of fecal coliforms and fulfils the required quality 6 for restricted irrigation. 16S rRNA gene-based high-throughput sequencing showed that several 7 genera associated with opportunistic pathogens (e.g. Acinetobacter, Aeromonas, Arcobacter, 8 Legionella, Mycobacterium, Neisseria, Pseudomonas and Streptococcus) were detected at 9 relative abundance ranging from 0.010 to 21 % of the total microbial community in the influent. 10

Membrane Bioreactor-Based Wastewater Treatment Plant in Saudi Arabia: Reduction of Viral Diversity, Load, and Infectious Capacity

“…However, infectious EV was detected in the chlorinated effluent and occasionally in concentrations approximating its 50% infectious dose. These results and those of an earlier study identified antibiotic-resistant bacteria and associated resistance genes in chlorinated effluent [1], indicating a need to implement good management practices (e.g., wearing personal protective gear or clothing) when irrigating fields with treated wastewater in the local context. The presence of plant viruses in chlorinated effluent raises concerns about reuse in commercial agricultural irrigation.…”

“…All samples have a coliform count lower than 2.2 CFU/100 mL and meet the maximum discharge requirement for unrestricted irrigation [1,2]. The coliform counts increased in the months experiencing a lower temperature (Table S2).…”

“…In developing countries, wastewater treatment plants utilize biological activated sludge for nutrient removal and physical processes to separate biomass from treated wastewater. Secondary biological treatment processes achieve satisfactory treatment with regards to fecal coliforms in wastewater, and generally are able to meet a local discharge requirement that includes a permissible level of fecal coliforms in wastewater <1000 CFU/100 mL for restricted irrigation or <2.2 CFU/100 mL for unrestricted irrigation [1,2].…”

Arcobacter

“…Given the potential for arcobacters to grow during sewage treatment, it was interesting to see that a recent study of secondary treatment WWTP in Saudi Arabia showed (by NGS) effective removal of certain genera such as Pseudomonas (4 log 10 reduction) and Arcobacter (2 log 10 reduction) from influent to effluent water (Al-Jassim et al, 2015). A further 1 log 10 removal of Arcobacter was achieved by chlorination.…”

Inactivation Effect of Antibiotic-Resistant Gene Using Chlorine Disinfection

“…Yuan et al [21] showed that all bacteria, except erythromycin-and sulfadiazine-resistant bacteria, were inactivated fully by 15 mg Cl 2 min/L, and a chlorine dose of > 60 mg Cl 2 min/L was needed to inactivate erythromycin-and sulfadiazine-resistant bacteria. Additionally, the proportion of multidrug-resistant bacteria isolated from the chlorinated effluent increases compared to the influent, and antibiotic-resistance genes remain detectable in the chlorinated effluent [25]. Huang et al [26] also indicated that tetracycline-resistant E. coli showed a higher resistance to chlorine than tetracycline-sensitive E. coli.…”