Mitigating risks and maximizing sustainability of treated wastewater reuse for irrigation.

Scarcity of freshwater for agriculture has led to increased utilization of treated wastewater (TWW), establishing it as a significant and reliable source of irrigation water. However, years of research indicate that if not managed adequately, TWW may deleteriously affect soil functioning and plant productivity, and pose a hazard to human and environmental health. This review leverages the experience of researchers, stakeholders, and policymakers from Israel, the United-States, and Europe to present a holistic, multidisciplinary perspective on maximizing the benefits from municipal TWW use for irrigation. We specifically draw on the extensive knowledge gained in Israel, a world leader in agricultural TWW implementation. The first two sections of the work set the foundation for understanding current challenges involved with the use of TWW, detailing known and emerging agronomic and environmental issues (such as salinity and phytotoxicity) and public health risks (such as contaminants of emerging concern and pathogens). The work then presents solutions to address these challenges, including technological and agronomic management-based solutions as well as source control policies. The concluding section presents suggestions for the path forward, emphasizing the importance of improving links between research and policy, and better outreach to the public and agricultural practitioners. We use this platform as a call for action, to form a global harmonized data system that will centralize scientific findings on agronomic, environmental and public health effects of TWW irrigation. Insights from such global collaboration will help to mitigate risks, and facilitate more sustainable use of TWW for food production in the future.

Bulk and water-extractable organic matter from compost: evaluation of the selective dissolution in water using infrared absorbance ratios.

Land application of composts affects concentration and composition of dissolved organic matter (OM) which plays important roles in soil functioning and may have effects on spreading of environmental pollution. Linking between the composition of bulk compost OM and its water-soluble fraction may, therefore, allow better understanding and prediction of the environmental impact of compost added to soil. The objectives of this study were to (i) examine composition-based links between bulk compost OM and water-extractable OM (WEOM), and (ii) evaluate and quantify selectivity of bulk compost OM dissolution, based on infrared (IR) absorbing functional groups. For that, 8 different composts and their freeze-dried WEOMs were characterized by mid-IR transmission spectroscopy. Compositions of compost OM and of WEOM were characterized in terms of ratios (R) defined on the basis of both areas and heights of specific IR absorbance bands in relation to absorbance by aliphatic CH groups. A simple novel approach is suggested, whereby selective dissolution of compost OM components is quantified by relating the R values determined for WEOM to those associated with compost OM. Significant similarities of IR spectra found in a series of WEOMs (and, to a lesser extent, in a series of compost OMs) suggest significant contributions of OM carboxylic groups to various bands. IR absorbance of compost OM contributed by hydrophilic and, specifically, carboxyl and carboxylate groups, when related to absorbance by aliphatic CH groups, can be used for predicting the indices characterizing WEOM composition, such as IR absorbance-based R values and aromaticity estimated from specific UV absorbance.

Soil health assessment: A critical review of current methodologies and a proposed new approach.

The wellbeing of soils is crucial for securing food production worldwide. The soil health (SH) concept has been introduced due to an evolving understanding that soil is not just a growing medium for crops but that it provides a foundation for other essential ecosystem services (ES). The SH concept requires development of a holistic index for reliable and quantitative assessment of soil wellbeing related to the effects of different soil management practices and land uses. The aims of this paper are to: (1) review current approaches and methods to assess SH, (2) highlight the role of soil ES in characterizing soil function and (3) propose a new approach to assess SH via monitoring of ES provided by soils. We introduce a brief critical review of the following three main steps required for assessment of common SH indices: (1) selection of relevant attributes; (2) quantification and scoring approaches; and (3) integration of the selected attributes to construct the SH index. These steps usually include statistical or expert opinion-based approaches. In addition, we present a new approach that highlights the relevance and importance of soil ES, i.e., provisioning, regulating and supporting services that must be quantified for comprehensive assessment of soil functions and for fitting models that relate selected soil attributes to ES. This will allow practitioners and scholars to identify the most significant and universal attributes, quantify the relative contribution of each attribute to each ES, and subsequently assess the overall health of soils.

Fluorescent components of organic matter in wastewater: efficacy and selectivity of the water treatment.

Characterization of organic matter (OM) present in treated wastewater (TWW) after various treatment stages is important for optimizing wastewater recycling. The general aim of this research was to carry out a long-term examination of OM in wastewater along the treatment, by applying excitation-emission matrices (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC). Fluorescent OM was examined in water samples obtained from four wastewater treatment plants (WWTPs) in Israel for 20 months. The PARAFAC analysis of EEMs of water samples from the four WWTPs yielded six components. The fluorescent components included proteinaceous tryptophan-like matter (C1), three humic-like components (C2-C4), a component (C5) that was characterized by excitation and emission with a distinct vibrational structure similar to that of pyrene and a component (C6) that was characterized by the excitation and emission spectra demonstrating two peaks where the appearance of two emission peaks was suggested to reflect the formation of an intra-molecular exyplex. The biological treatment strongly reduced the concentration of component C1 thus increasing the overall fraction of humic-like OM over the proteinaceous OM in the treated water. The fluorescence of component C1 could therefore be used as an indicator of the biological treatment efficacy. The concentration of the humic-like component C2 characterized by excitation and emission maxima at <240,305/422 nm, respectively, was also sensitive to biological treatment. The soil aquifer treatment was not effective in completely eliminating the fingerprints of the initial wastewater. The concentrations of the fluorescent components in wastewater after the biological treatment were only slightly affected by filtration (0.45 µm) of the samples. For water sampled prior to the biological treatment, the 0.45 µm filtration had the most pronounced effect on concentrations of the proteinaceous matter and component C6. Strong positive correlations were found between concentrations of component C1 and total carbon (TC) in wastewater samples from the WWTPs thus suggesting the proteinaceous fluorescence in wastewater as an indicator for TC reduction. Chemical oxygen demand (COD) and the fluorescein diacetate hydrolyzing activity (a measure for the total microbial activity) were strongly positively correlated with the concentrations of components C1-C3 thus suggesting the fluorescence of these components as indicators for reduction in COD and the total microbial activity in wastewater.