Nikolaos V. Paranychianakis

Treatment of Wastewater With Slow Rate Systems: A Review of Treatment Processes and Plant Functions

Land treatment systems constitute a viable alternative solution for wastewater management in cases where the construction of conventional (mechanical) wastewater treatment plants (WWTPs) are not affordable or other disposal options are not available. They have proven to be an ideal technology for small rural communities, clusters of homes, and small industrial units due to low energy demands and low operation and maintenance costs. In addition, slow rate systems (SRS) may be designed using the “zero discharge” concept. The purpose of this article is to review the current trends and developments in the field of SRS, focusing on those systems in which effluent application is based on plant water requirements. Vegetation has an important role in treatment efficiency through its effects on hydraulic loading rate, nutrient removal, and biomass production. In addition, vegetation may affect the fate of trace elements and the degradation/detoxification of recalcitrant organics. Detailed knowledge of the basic processes involved in wastewater treatment and the factors governing the performance of SRS is fundamental for enhancing treatment efficiency and eliminating potential environmental and health risks. Finally, monitoring performance of SRS and adopting the appropriate management strategies are of paramount importance to maintain treatment efficiency over the a long term.

Water Reuse in EU States: Necessity for Uniform Criteria to Mitigate Human and Environmental Risks

Water quality criteria are an indispensable part of water reuse projects aiming to ensure the protection of public health and the environment. In addition, criteria can affect the development, public acceptance, and economic viability of water reuse projects. Currently no uniform criteria exist, but they diverge, often greatly, between countries and states. The authors briefly present the evolution of reuse criteria worldwide and discuss emerging issues related to ecological and public health risks that have not addressed adequately in existing criteria. They specifically focus on European Union (EU) countries and present their water reuse status based on the published data and the existing (or nonexisting) reuse frameworks. Data gathered from public agencies reveal a high potential for water reuse in the EU that could potentially contribute to ensuring that fresh water is available for all sectors and to protect the environment, but it has not expanded at the expected rates. The lack of water reuse criteria was thought as the most important cause for this delay. lasting recent years, however, several countries, particularly those located in the Mediterranean basin, established water reuse criteria. Similarities and differences as well as potential benefits and drawbacks of these criteria are discussed and interpreted with these of the other world. An important conclusion is that the criteria enacted in Greece, Italy, and Spain will probably prevent the development of water reuse projects and increase the costs. Moreover, major challenges, the future views, and the necessity for establishing common regulations for water reuse at an EU level are considered.

Effects of Municipal Solid Waste Compost on Soil Properties and Vegetables Growth

ABSTRACT This work investigates the impact of municipal solid waste compost (MSW-compost) application (0, 50, and 100 t/ha) on the growth, and on nutrient and trace elements content in lettuce and tomato plants grown in large, 40-L pots. Our findings showed inhibition of plants’ growth with increasing dose of MSW-compost, compared to plants receiving conventional fertilization. Growth inhibition was associated with a sharp decrease in soil NO3–N content. On the other hand, a slower decrease in soil NO3–N content occurred in non-planted pots amended with MSW-compost. These findings provide evidence that N immobilization and/or decreased N mineralization were responsible for inhibited growth by constraining N availability. With regard to the other macro-nutrients, K, P, Mg, Ca, and Fe, their contents in leaves of both crops were maintained at optimum levels. Higher zinc and copper content was measured in leaves of both crops but they did not exceed the optimum range for growth. No accumulation of trace elements was found in the fruits. The content of heavy metals in the tissues of plants grown in MSW-compost amended soil, remained at levels similar to those of the non-amended soil, suggesting that they do not pose a significant risk either for plant growth or public health. The findings of our study suggest that further emphasis should be given on the investigation of the factors regulating N mineralization and availability in order to avoid reductions in crop yield.

Sediment provenance, soil development, and carbon content in fluvial and manmade terraces at Koiliaris River Critical Zone Observatory

PurposeThe purpose of this study was the investigation of sediment provenance and soil formation processes within a Mediterranean watershed (Koiliaris CZO in Greece) with particular emphasis on natural and manmade terraces.Material and methodsFive sites (K1–K5) were excavated and analyzed for their pedology (profile description), geochemistry [including rare earth elements (REEs) and other trace elements], texture, and mineralogy along with chronological analysis (optical luminescence dating). The selected sites have the common characteristic of being flat terraces while the sites differed with regard to bedrock lithology, elevation, and land use.Results and discussionThree characteristic processes of soil genesis were identified: (1) sediments transportation from outcrops of metamorphic rocks and sedimentation at the fluvial sites (K1–K2), (2) in situ soil development in manmade terraces (K3, K4), and (3) strong eolian input and/or material transported by gravity from upslope at the mountainous site (K5). REE patterns verified the soil genesis processes while they revealed also soil development processes such as (a) calcite deposition (K1), (b) clay illuviation and strong weathering (K4), and (c) possibly fast oxidation/precipitation processes (K3). Carbon sequestration throughout the soil profile was high at manmade terraces at higher elevation compared to fluvial environments due to both climatic effects and possibly intensive anthropogenic impact.ConclusionsSoils at Koiliaris CZO were rather young soils with limited evolution. The different soil age, land use, and climatic effect induced various soil genesis and soil development processes. The manmade terraces at higher elevation have much higher carbon sequestration compared to the anthropogenic impacted fluvial areas.

Environmental drivers of the distribution of nitrogen functional genes at a watershed scale

To date only few studies have dealt with the biogeography of microbial communities at large spatial scales, despite the importance of such information to understand and simulate ecosystem functioning. Herein, we describe the biogeographic patterns of microorganisms involved in nitrogen (N)-cycling (diazotrophs, ammonia oxidizers, denitrifiers) as well as the environmental factors shaping these patterns across the Koiliaris Critical Zone Observatory, a typical Mediterranean watershed. Our findings revealed that a proportion of variance ranging from 40 to 80% of functional genes abundance could be explained by the environmental variables monitored, with pH, soil texture, total organic carbon and potential nitrification rate being identified as the most important drivers. The spatial autocorrelation of N-functional genes ranged from 0.2 to 6.2 km and prediction maps, generated by cokriging, revealed distinct patterns of functional genes. The inclusion of functional genes in statistical modeling substantially improved the proportion of variance explained by the models, a result possibly due to the strong relationships that were identified among microbial groups. Significant relationships were set between functional groups, which were further mediated by land use (natural versus agricultural lands). These relationships, in combination with the environmental variables, allow us to provide insights regarding the ecological preferences of N-functional groups and among them the recently identified clade II of nitrous oxide reducers.

Environmental drivers of soil microbial community distribution at the Koiliaris Critical Zone Observatory.

Data on soil microbial community distribution at large scales are limited despite the important information that could be drawn with regard to their function and the influence of environmental factors on nutrient cycling and ecosystem services. This study investigates the distribution of Archaea, Bacteria and Fungi as well as the dominant bacterial phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes), and classes of Proteobacteria (Alpha- and Betaproteobacteria) across the Koiliaris watershed by qPCR and associate them with environmental variables. Predictive maps of microorganisms distribution at watershed scale were generated by co-kriging, using the most significant predictors. Our findings showed that 31-79% of the spatial variation in microbial taxa abundance could be explained by the parameters measured, with total organic carbon and pH being identified as the most important. Moreover, strong correlations were set between microbial groups and their inclusion on variance explanation improved the prediction power of the models. The spatial autocorrelation of microbial groups ranged from 309 to 2.226 m, and geographic distance, by itself, could explain a high proportion of their variation. Our findings shed light on the factors shaping microbial communities at a high taxonomic level and provide evidence for ecological coherence and syntrophic interactions at the watershed scale.