Characteristics and Driven Factors of Nitrous Oxide and Carbon Dioxide Emissions in Soil Irrigated with Treated Wastewater

The reuse of treated wastewater in agricultural systems could partially help alleviate water resource shortages in developing countries. Treated wastewater differs from fresh water in that it has higher concentrations of salts, Escherichia coli and presence of dissolved organic matter, and inorganic N after secondary treatment, among others. Its application could thus cause environmental consequences such as soil salinization, ammonia volatilization, and greenhouse gas emissions. In an incubation experiment, we evaluated the characteristics and effects of water-filled pore space （WFPS） and N input on the emissions of nitrous oxide （N2O） and carbon dioxide （CO2） from silt loam soil receiving treated wastewater. Irrigation with treated wastewater （vs. distilled water） significantly increased cumulative N2O emission in soil （117.97 μg N kg-1）. Cumulative N2O emissions showed an exponentially increase with the increasing WFPS in unamended soil, but the maximum occurred in the added urea soil incubated at 60% WFPS. N2O emissions caused by irrigation with treated wastewater combined with urea-N fertilization did not simply add linearly, but significant interaction （P〈0.05） caused lower emissions than the production of N2O from the cumulative effects of treated wastewater and fertilizer N. Moreover, a significant impact on cumulative CO2 emission was measured in soil irrigated with treated wastewater. When treated wastewater was applied, there was significant interaction between WFPS and N input on N2O emission. Hence, our results indicated that irrigation with treated wastewater should cause great concern for increasing global warming potential due to enhanced emission of N2O and CO2.

Potential risk of soil irrigation with treated wastewater over 40 years:a field experiment under semi-arid conditions in northeastern Tunisia

In Tunisia,water scarcity is only adding pressure on water demand in agriculture.In the context of sustainable development goals,Tunisia has been reusing treated wastewater(TWW)as a renewable and inexpensive source for soil fertigation and groundwater(GW)recharge.However,major risks can be expected when the irrigation water is of poor quality.This study aims for evaluating the potential risk of TWW and GW irrigation on soil parameters.Accordingly,we evaluated the suitability of water quality through the analysis of major and minor cations and anions,metallic trace elements(MTEs),and the sodium hazard by using the sodium adsorption ratio(SAR)and the soluble sodium percentage(SSP).The risk of soil sodicity was further assessed by SAR and the exchangeable sodium percentage(ESP).The degree of soil pollution caused by MTEs accumulation was evaluated using geoaccumulation index(Igeo)and pollution load index(PLI).Soil maps were generated using inverse spline interpolation in ArcGIS software.The results show that both water samples(i.e.,TWW and GW)are suitable for soil irrigation in terms of salinity(electrical conductivity<7000μS/cm)and sodicity(SAR<10.00;SSP<60.00%).However,the contents of PO_(4)^(3-),Cu^(2+),and Cd^(2+)exceed the maximum threshold values set by the national and other standards.Concerning the soil samples,the average levels of SAR and ESP are within the standards(SAR<13.00;ESP<15.00%).On the other hand,PLI results reveal moderate pollution in the plot irrigated with TWW and no to moderate pollution in the plot irrigated with GW.Igeo results indicate that Cu^(2+)is the metallic trace element(MTE)with the highest risk of soil pollution in both plots(Igeo>5.00),followed by Ni^(2+)and Pb^(2+).Nevertheless,Cd^(2+)presents the lowest risk of soil pollution(Igeo<0.00).Statistical data indicates that Ca^(2+),Na+,Ni^(2+),and Pb^(2+)are highly distributed in both plots(coefficient of variation>50.0%).This study shows that the use of imagery tools,such as ArcGIS,can provide important information for evaluating the current status of soil fertility or pollution and for better managing soil irrigation with TWW.

Water quality of reclaimed water from treated urban wastewater in Chaobai River Basin,North China

The utilization of reclaimed water could be an efficient tool to alleviate water scarcity,especially for dry river augmentation.However,it is crucial to monitor water quality to ensure safety to human health and to avoid negative effects on the environment.Reclaimed water samples were collected bimonthly from May to November in 2010 in Chaobai River,and the physiochemical parameters were determined.The main results are as follows:The parameters exceeding the threshold value of the water guidelines are mainly nutrition related to nitrogen and phosphorus,which are known to increase the risk of eutrophication in surface waters.Additionally,nitrite and nitrate can be detrimental to human health.The majority of the parameters have a peaking concentration in May,whereas others either show significant temporal variation over the entire period or remain relatively constant in all four months.Correlation analysis shows that some parameters(pH,T and B) have no significant correlation with others,whereas significant positive correlation was found for Sr with EC and TDS,for CI with TDS,for Si02 with TP and for NO3-N with TN and a significant negative correlation between SO4 and Ba.According to principal component analysis,60.108%of the total data is represented by dominant solutes,and the second principal component with a percentage of 31.876 comprises parameters related to nitrogen.Subsequent cluster analysis of parameters identified four groups,which represent different compositions,and samples in May differ from others.

Advanced Treatment of Biologically Treated Chemical Comprehensive Wastewater by Nano-TiO2 Photocatalytic Oxidation

Nano-TiO2 photocatalytic oxidation was used to perform the advanced treatment of biologically treated chemical comprehensive wastewater. The effects of reaction time,nano-TiO2 dosage and initial p H of the wastewater on the removal rate of COD were tested. The GC/MS and EEM techniques were used to qualitatively analyze organic compounds in the wastewater before and after treatment. The result showed that after the biologically treated chemical comprehensive wastewater was treated by nano-TiO2 photocatalytic oxidation under the conditions of reaction time 3 h,nano-TiO2 dosage 8 g/L,and pH 8. 0,the effluent COD was 61. 9 mg/L and its removal rate was 63. 8%. Additionally,the species of organic pollutants reduced from 12 to 6. Meanwhile,the content of humic-like and fulvic-like substances dropped dramatically.

The Response of Chickpea to Irrigation with Treated Waste Water

In a three-year study, the response of four cultivars of chickpea, Bulgarit, WIR-32, Jordan and ICC 11293 to irrigation with TW （treated wastewater） and FW （freshwater）, using surface and subsurface drip irrigation was investigated. Wastewater generated from Al-Quds university campus included black, grey and storm water was treated by small scale pilot plant. The wastewater pilot plant consists of tailored made secondary biological activated sludge process with daily capacity of 50 m3. The influent and effluent chemical and biological quality parameters were routinely monitored and analyzed. The data reveal that the average values for BOD, COD and EC for the effluent are 50 ppm, 136 ppm and 1.4 mS/cm over 2 years period. The results of chickpea growth parameters and the chemical and biological analysis of the seeds and leaves indicate that the cultivars Bulgarit and ICC 11293 can be irrigated with TW without any loss in yield and quality. Factor analysis reasonably favored Bulgarit Cultivar irrigated with treated effluent over other cultivars. WIR-32 and Jordan cultivars showed significant reduction in their growth parameters when irrigated with TW as compared with FW. Surface and subsurface drip irrigation gave similar results in most cases. Soil analysis in this study showed no significant difference between irrigation with TW and FW.

Metagenomic and viromic data mining reveals viral threats in biologically treated domestic wastewater

Activated sludge(AS),a common biological secondary treatment process in wastewater treatment plants(WWTPs),is known to remove a large spectrum of microorganisms.Yet little is known about its effect on the entire viral community.After compiling 3 Tbp of next-generation sequencing(NGS)metagenomic/viromic datasets consisted of 119 sub-datasets of influent,effluent,and AS samples from 27WWTPs,viral removal efficacy is evaluated through data mining.The normalized abundance of viruses suggests effluents exhibit the highest viral prevalence(3.21±3.26%,n=13)followed by the AS(0.48±0.25%,n=57)and influents(0.23±0.17%,n=17).In contrast,plasmids,representing genetic element of bacteria,show higher average prevalence(0.73±0.82%,n=17)in influents than those of the AS(0.63±0.26%,n=57)and effluents(0.35±0.42%,n=13).Furthermore,the abundance-occupancy analysis identifies 142 core phage viruses and 17 non-phages core viruses,including several pathogenic viruses in the AS virome.The persistent occurrence of pathogenic viruses,coupled with nonfavorable virus removal by the AS treatment,reveals the hidden virus threats in biologically treated domestic wastewater.The mechanisms for why viruses persist and the possibility that WWTPs are potential hotspots for viral survival deserve attention.

Microbial Quality of Irrigation Water of Public Parks in Dubai, United Arab Emirates

In this study, the microbial quality of treated wastewater used for irrigation of three public parks in Dubai was evaluated. A total of 23 samples of TWW （treated wastewater） and 12 samples of irrigated soils from three public parks were collected and tested for Legionella, Salmonella, traditional bacterial indicators, Cryptosporidium oocyst and Giardia cysts using membrane filtration and direct immune-fluorescence assay. The majority of the tested water samples were found contaminated with LLO （Legionella like organisms）, Salmonella and traditional bacterial indicators. Both Cryptosporidium oocysts and Giardia cysts were detected in these samples with a higher occurrence ofCryptosporidium oocysts （96%） than Giardia cysts （35%）. The fecal coliform bacteria were detected in 60.8% of water samples and 58% of soil samples. Total coliform bacteria were detected in most of the water and soil samples with a higher occurrence than the fecal coliform bacteria. The results of this study indicate that microorganisms are surviving the chlorination method used for disinfecting wastewater, and are further multiplying in the public parks irrigation network system. Therefore, monitoring the treated wastewater for bacterial pathogens, protozoan parasites and controlling their growth at the point of end use are vital to reducing the risk of environmental contamination with microbial pathogens.

Soil properties and habitats determine the response of bacterial communities to agricultural wastewater irrigation

Increasing temperatures and variability of precipitation events due to climate change will lead in the future to higher irrigation demands in agroecosystems.However,the use of secondary treated wasterwater(TWW)could have consequences for the receiving soil environment and its resident microbial communities.The objective of this study was to characterize the importance of soil properties and habitats to the response of soil bacteria and archaea to irrigation with TWW.Two agricultural soils with contrasting textures(loamy sand or silt loam)and,for each,three variants differing in soil organic carbon and nitrogen,as generated by long-term fertilization,were analyzed.For each of these six soils,prokaryotic communities from two habitats,i.e.,root-free bulk soil and the rhizosphere of developing cucumber plants in the greenhouse,were characterized.Communities were analyzed by the quantity and diversity of their polymerase chain reaction(PCR)-amplified 16S rRNA genes.To account for TWW-associated nutrient effects,potable water(PW)served as a control.Amplicon sequence analysis showed that prokaryotic communities mainly consisted of bacteria(99.8%).Upon irrigation,regardless of the water quality,prokaryotic diversity declined,p H increased,and no bacterial growth was detected in bulk soil.In contrast,the growth of cucumbers was stimulated by TWW,indicating that plants were the main beneficiaries.Moreover,strong responses were seen in the rhizosphere,suggesting an indirect effect of TWW by altered rhizodepositions.The main bacterial responders to TWW were Proteobacteria,Bacteroidetes,Actinobacteria,and Planctomycetes.Changes in bacterial communities due to TWW were less pronounced in all variants of the silt loam,indicating the importance of clay and soil organic carbon for buffering effects of TWW on soil bacterial communities.Hence,soil organic carbon and soil texture are important parameters that need to be considered when applying TWW in agriculture.

Effect of Water Quality on Heavy Metal Redistribution and Mobility in Polluted Agricultural Soils in a Semi-Arid Region

Mornag Plain is a coastal area of the Mediterranean basin, which has undergone an agricultural industrial boom. The aim of this study was to investigate the different water qualities used for irrigation on heavy metal mobility in these polluted agricultural soils. The geo-accumulation indices for heavy metals (Ni, Cr, Pb, Cd, Cu, and Zn) revealed that industrial activities and used treated wastewater (TWW) contributed to soil pollution, and water irrigation always decreased this contamination. After long-term use of different water types, high perturbation of heavy metal redistribution has occurred. Groundwater use altered all heavy metal redistributions in the irrigated soil among various soil-solid and soil-solution fractions, as compared to the unirrigated soil. Slight acid water use transferred some metals from different solid phase components into water-soluble and exchangeable fractions. However, TWW use transformed some Ni, Cr, Cd, Cu, and Zn from water-soluble and exchangeable fractions to less labile fractions, particularly into organically bound fractions. Reuse of conventional water within the same soil decreased the whole soil redistribution index values, indicating tendency to return to the pattern of distribution of groundwater-irrigated soil.