Spectroscopic and microscopic characterization of humic acids from composts made by co-composting of green waste, spent coffee and OMWW sludge.

Due to its important role in the formation of humic acids (HA), improving lignin degradation during composting has usually been considered a challenge. One practice that could stimulate the biodegradation of this recalcitrant molecule is inoculation with exogenous lignolytic fungal strains. Two composts (C1) and (C2) from piles (H1) and (H2) were evaluated. H1 was the control pile and H2 was inoculated at maturity with Trametes trogii, resulting in a 35% increase in lignin degradation rate compared to H1. The aim of this study was to show the main effects of this increase on the humification process in the co-composting of green waste, coffee grounds and olive mill wastewater sludge (OMWWs). Microstructure of HA1 and HA2 extracted from C1 and C2, respectively, was also investigated by scanning electron microscopy (SEM) and SEM coupled with energy-dispersive X-ray spectroscopy (X-EDS). The results showed that there were several similarities between the compost samples tested. These included the mineral content, the degree of polymerization (PD)> 1 and the compact and rigid surface of the extracted HA. However, C2 was characterized by a higher humic content (HC), degree of polymerization (PD), humification index (HI) and percentage of humic acids (PHA) than C1. Carbon-13 nuclear magnetic resonance (13C-NMR) and Fourier transmission-infrared spectroscopy (FTIR) analysis showed that aliphatic groups such as hydroxyls, alcohols and carboxyls were predominant in both composts. SEM analysis in conjunction with X-EDS analysis of HA2 showed a higher proportion of carbon and potassium (18 and 7.93%) than in HA1 (14 and 0.95%).

Co-occurrence of antibiotic and metal resistance in long-term sewage sludge-amended soils: influence of application rates and pedo-climatic conditions.

Urban sewage sludge (USS) is increasingly being used as an alternative organic amendment in agriculture. Because USS originates mostly from human excreta, partially metabolized pharmaceuticals have also been considered in risk assessment studies after reuse. In this regard, we investigated the cumulative effect of five annual USS applications on the spread of antibiotic-resistant bacteria (ARB) and their subsequent resistance to toxic metals in two unvegetated soils. Eventually, USS contained bacterial strains resistant to all addressed antibiotics with indices of resistance varying between 0.25 for gentamicin to 38% for ampicillin and azithromycin. Sludge-amended soils showed also the emergence of resistome for all tested antibiotics compared to non-treated controls. In this regard, the increase of sludge dose generally correlated with ARB counts, while soil texture had no influence. On the other hand, the multi-antibiotic resistance (MAR) of 52 isolates selected from USS and different soil treatments was investigated for 10 most prescribed antibiotics. Nine isolates showed significant MAR index (≥ 0.3) and co-resistance to Cd, As and Be as well. However, events including an extreme flash flood and the termination of USS applications significantly disrupted ARB communities in all soil treatments. In any case, this study highlighted the risks of ARB spread in sludge-amended soils and a greater concern with the recent exacerbation of antibiotic overuse following COVID-19 outbreak.

Variation of soil properties with sampling depth in two different light-textured soils after repeated applications of urban sewage sludge.

Semi-arid agricultural soils have increasingly been subjected to urban sewage sludge (USS) applications due to accelerated soil depletion and shortages in manure supply. Research studies addressing USS reuse have mostly been conducted in cropping systems and focused on changes in topsoil properties of a given texture. Therefore, sludge-soil interactions could be largely influenced by the presence of plants, soil particle composition and depth. In this field study, two agricultural soils (sandy, S and sandy loam, SL) received simultaneously four annual USS applications of 40, 80, and 120 t ha-1 year-1 in absence of vegetation. Outcomes showed the increase of carbon and macronutrients in both soils proportionally to USS dose especially in the topsoil profile (0-20 cm). Subsoil (20-40 cm) was similarly influenced by sludge rates, showing comparable variations of fertility parameters though at significant lower levels. The depth-dependent improvement of soil fertility in both layers enhanced the microbiological properties accordingly, with significant variations in soil SL characterized by a higher clay content than soil S. Besides, positive correlations between increases in sludge dose, salinity, trace metals, and enzyme activities in both soils indicate that excessive sludge doses did not cause soil degradation or biotoxic effects under the described experimental conditions. In particular and despite high geoaccumulation indices of Ni in both soils and profiles, the global concentrations of Cu, Ni, Pb, and Zn were still below threshold levels for contaminated soils. In addition, the maintenance of pH values within neutral range and the increase of organic matter content with respect to control would have further reduced metal availability in amended soils. Therefore, we could closely investigate the effects of texture and depth on the intrinsic resilience of each soil to cope with repetitive USS applications.

Carbon mineralization, biological indicators, and phytotoxicity to assess the impact of urban sewage sludge on two light-textured soils in a microcosm.

The agricultural reuse of urban sewage sludge (USS) modifies soil properties depending on sludge quality, management, and pedo-environmental conditions. The aim of this microcosm study was to assess C mineralization and subsequent changes in soil properties after USS addition to two typical Mediterranean soils: sandy (Soil S) and sandy loam (Soil A) at equivalent field rates of 40 t ha-1 (USS-40) and 120 t ha-1 (USS-120). Outcomes proved the biodegradability of USS through immediate CO2 release inside incubation bottles in a dose-dependent manner. Accordingly, the highest rates of daily C emission were recorded with USS-120 (3.7 and 3.9 mg kg-1 d-1 for Soils S and A, respectively) after 84 d of incubation at 25 °C. The addition of USS also improved soil fertility by enhancing soil macronutrients, microbial proliferation, and protease activity. Protease showed significant correlation with N, total organic C, and heterotrophic bacteria, reflecting the biostimulation and bioaugmentation effects of sludge. Soil indices like C/N/P stoichiometry and metabolic quotient (qCO2 ) varied mostly with mineralization rates of C and P in both soils. Despite a significant increase of soil salinity and total heavy metal content (lead, nickel, zinc, and copper) with USS dose, wheat germination was not affected by these changes. Both experimental soils showed intrinsic (Soil A) and incubation-induced (Soil S) phytotoxicities that were alleviated by USS addition. This was likely due to the enhancement of biodegradation and/or retention of phytotoxicants originating from previous land uses. Urban sewage sludge amendments could have applications in soil remediation by reducing the negative effects of allelopathic and/or anthropogenic phytoinhibitors.

Impact of urban sewage sludge on soil physico-chemical properties and phytotoxicity as influenced by soil texture and reuse conditions.

Urban sewage sludge (USS) is increasingly applied to agricultural soils, but mixed results have been reported because of variations in reuse conditions. Most field trials have been conducted in cropping systems, which conceal intrinsic soil responses to sludge amendments due to the rhizosphere effect and farming practices. Therefore, the current field study highlights long-term changes in bare soil properties in strict relationship with soil texture and USS dose. Two agricultural soils (loamy sand [LS] and sandy [S]) were amended annually with increasing sludge rates up to 120 t ha-1 yr-1 for 5 yr under unvegetated conditions. Outcomes showed a USS dose-dependent variation of all studied parameters in topsoil samples. Soil salinization was the most significant risk related to excessive USS doses. Total dissolved salts (TDS) in saturated paste extracts reached the highest concentrations of 37.2 and 43.1 g L-1 in S soil and LS soil, respectively, treated with 120 t USS ha-1 yr-1 . This was also reflected by electrical conductivity of the saturated paste extract (ECe ) exceeding 4,000 µS cm-1 in both treatments. As observed for TDS, fertility indicators and bioavailable metals varied with soil texture due to the greater retention capacity of LS soil owing to higher fine fraction content. Soil phytotoxicity was estimated by the seed germination index (GI) calculated for lettuce, alfalfa, oat, and durum wheat. The GI was species dependent, indicating different degrees of sensitivity or tolerance to increasing USS rates. Lettuce germination was significantly affected by changes in soil conditions showing negative correlations with ECe and soluble metals. In contrast, treatment with USS enhanced the GI of wheat, reflecting higher salinity tolerance and a positive effect of sludge on abiotic conditions that control germination in soil. Therefore, the choice of adapted plant species is the key factor for successful cropping trials in sludge-amended soils.

Community-level genetic profiles of actinomycetales in long-term biowaste-amended soils.

Actinomycetales is an order of actinobacteria that have an important role in the decomposition of organic matter. Their abundance and distribution can reflect a good level of soil fertility as well as biological activity. In this research study, actinomycetal diversity in soil was investigated under various field treatments with biowastes. Initially, unvegetated agricultural soil plots of 4 m2 had been annually amended with increasing rates of municipal solid waste compost (MSWC at 40, 80 and 120 t ha-1 year-1) and farmyard manure (FM at 40 and 120 t ha-1 year-1) for eight consecutive years. Control consisted of unamended soil and all treatments were distributed in four randomized complete blocks. At the end of the experimental period, total DNA was extracted from fresh topsoil samples (0-20 cm) then nested PCR-DGGE sequencing method was applied to assess the long-term effect of treatments on the diversity of actinomycetes. Analytical outcomes revealed the presence of ten actinomycetal families with Streptomycetaceae, Pseudonocardiaceae and Nocardioidaceae being the most dominant regardless to changes in experimental conditions. Besides, the long-term accumulation of both biowastes in soil affected the diversity of actinomycetal communities in different ways including contribution, stimulation or inhibition. Interestingly, soil treated with MSWC at an equivalent rate of 40 t ha-1 year-1 was likely to provide optimal growth conditions for major identified genera because it showed the highest actinomycetal diversity as compared to the rest of the treatments.

Comparative study on pilots between ANAMMOX favored conditions in a partially saturated vertical flow constructed wetland and a hybrid system for rural wastewater treatment.

The objective of this research was to evaluate the nitrogen removal in a single stage rural wastewater treatment system. It was a modified subsurface vertical flow (SSVF) constructed wetland. The so-called Anaerobic Ammonium Oxidation(ANAMMOX) process is favored by imposing a saturated zone at the bottom of the basin. The nitrogen removal performances of this modified SSVF were compared to those of a conventional hybrid system where the well-known nitrification-denitrification process is performed. This study was carried out using three lab-scale pilots of constructed wetlands during four months: (1) a hybrid constructed wetlands with a reed-Phragmites australis SSVF bed in serial with a cattail-Typha angustofolia SSHF bed (SSVFp + SSHF). (2) A reed-Phragmites australis SSVF bed partially saturated at 40% of its depth (SSVFPS); (3) A cattail-Typha angustofolia SSVF bed partially saturated at 40% of its depth (SSVFTS). The results showed that the three configurations used in this study were efficient for most of the pollutants reduction. In fact, single-stage reactors have achieved similar chemical oxygen demand (COD) removal in comparison to the two-stage reactor independently of the macrophytes species. However, for Total Kjeldahl Nitrogen (TKN), a slightly higher nitrogen removal efficiency was recorded for (SSVF p + SSHF) with an average removal rate of 53% versus 48% and 51% for SSVF PS and SSVFTS respectively. These findings were highlighted with fluorescent in situ hybridization (FISH) analysis, which demonstrated the presence of major differences in the community composition and abundance of the bacteria involved with denitrification and nitrification in the three systems. In fact, SSVFP of the hybrid system was characterized by highest relative abundance of nitrifying bacteria (13% Nitrosomonas, 11% Nitrosospira, 14% Nitrospira and 10% Nitrobacter). While, the SSHF of hybrid system had larger number of denitrifying species than SSVF, with relative abundances of pseudomonas (3%), Paracoccus (9%), Zoogloea (6%), Thauera (4%), Thiobacillus (2%) and Aeromonas (1%). Interestingly, in the SSVFST (planted with Thypha angustofolia) where the relative abundance of nitrifying bacteria was very low (4% Nitrosomonas, 4% Nitrosospira, 4% Nitrospira and 1% Nitrobacter), we have detected the presence of ANAMMOX bacteria (3%). Accordingly SSVFST in the presence of Thypha angustofolia have favored the development of ANAMMOX activity in comparison to the other configurations.

Effects of short- and long-term exposures of humic acid on the Anammox activity and microbial community.

Humic acid has a controversial effect on the biological treatment processes. Here, we have investigated humic acid effects on the Anammox activity by studying the nitrogen removal efficiencies in batch and continuous conditions and analyzing the microbial community using Fluorescence in situ hybridization (FISH) technique. The results showed that the Anammox activity was affected by the presence of humic acid at a concentration higher than 70 mg/L. In fact, in the presence of humic acid concentration of 200 mg/L, the Anammox activity decreased to 57% in batch and under continuous condition, the ammonium removal efficiencies of the reactor decreased from 78 to 41%. This reduction of Anammox activity after humic acid addition was highlighted by FISH analysis which revealed a considerable reduction of the abundance of Anammox bacteria and the bacteria living in symbiosis with them. Furthermore, a total inhibition of Candidatus Brocadia fulgida was observed. However, humic acid has promoted heterotrophic denitrifying bacteria which became dominant in the reactor. In fact, the evolution of the organic matter in the reactor showed that the added humic acid was used as carbon source by heterotrophic bacteria which explained the shift of metabolism to the favor of heterotrophic denitrifying bacteria. Accordingly, humic acid should be controlled in the influent to avoid Anammox activity inhibition.

Seasonal toxicity variation in light-textured soil amended with urban sewage sludge: interaction effect on cadmium, nickel, and phytotoxicity.

Sewage sludge is increasingly used as an organic amendment to agricultural soils, especially to soils containing little organic matter. However, little is known on the impact of this biowaste on seasonal changes of nickel and cadmium toxicity in a sandy loam soil. Accordingly, the aim of this field-scale study was to evaluate the seasonal phytotoxicity according to Cd, Ni, and dehydrogenase variation in an agricultural soil during two successive annual amendments with increasing amounts of urban sludge (0, 40, 80, and 120 t ha-1 year-1). Sampling was carried out at the end of dry season (EDS) and at the end of wet season (EWS) during 2 years 2012/2013. Sludge application significantly increased the amount of organic matter and dehydrogenase activity in the soil. In order to explain the seasonal variation of Cd and Ni, pH and electrical conductivity were also monitored in this study. The increased rate of sewage sludge addition slightly reduced the pH but soil remained above neutrality. The electrical conductivity which reflects soil salinity was strongly correlated with Cd and Ni content that increased with sludge dose. Salinity and heavy metals were highest at EDS 2013. In addition, soil phytotoxicity testing was performed by the evaluation of lettuce seed germination for 120 h. Although heavy metal content did not generally exceed Tunisian thresholds (3 and 75 mg kg-1 for Cd and Ni, respectively), the seed germination index decreased with sewage sludge dose at all seasons. In general, we observed a significant effect of seasonal variation for all studied parameters. Sewage sludge reuse could be a feasible way to improve soil organic matter but toxicity risks consistently increased with time.

Depletion of pentachlorophenol in soil microcosms with Byssochlamys nivea and Scopulariopsis brumptii as detoxification agents.

Pentachlorophenol (PCP) is a toxic compound which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Fungal bioremediation is an emerging approach to rehabilitating areas fouled by recalcitrant xenobiotics. In the present study, we isolated two fungal strains from an artificially PCP-contaminated soil during a long-term bioremediation study and evaluated their potential as bioremediation agents in depletion and detoxification of PCP in soil microcosms. The two fungal strains were identified as: Byssochlamys nivea (Westling, 1909) and Scopulariopsis brumptii (Salvanet-Duval, 1935). PCP removal and toxicity were examined during 28 days of incubation. Bioaugmented microcosms revealed a 60% and 62% PCP removal by B. nivea and S. brumptii, respectively. Co-inoculation of B. nivea and S. brumptii showed a synergetic effect on PCP removal resulting in 95% and 80% PCP decrease when initial concentrations were 12.5 and 25 mg kg-1, respectively. Detoxification in bioaugmented soil and the efficient role of fungi in the rehabilitation of PCP contaminated soil were experimentally proven by toxicity assays. A decrease in inhibition of bioluminescence of Escherichia coli HB101 pUCD607 and an increase of germination index of mustard (Brassica alba) seeds were observed in the decontaminated soils.

Evaluation of a hybrid anaerobic biofilm reactor treating winery effluents and using grape stalks as biofilm carrier.

Wine production processes generate large amount of both winery wastewater and solid wastes. Furthermore, working periods, volumes and pollution loads greatly vary over the year. Therefore, it is recommended to develop a low-cost treatment technology for the treatment of winery effluents taking into account the variation of the organic loading rate (OLR). Accordingly, we have investigated the sequential operation of an anaerobic biofilm reactor treating winery effluents and using grape stalks (GSs) as biofilm carrier with an OLR ranging from 0.65 to 27 gCOD/L/d. The result showed that, during the start-up with wastewater influent, the chemical oxygen demand (COD) removal rate ranged from 83% to 93% and was about 91% at the end of the start-up period that lasted for 40 days. After 3 months of inactivity period of the reactor (no influent feeding), we have succeeded in restarting-up the reactor in only 15 days with a COD removal of 82% and a low concentration of volatile fatty acids (1 g/L), which confirms the robustness of the reactor. As a consequence, GSs can be used as an efficient carrier support, allowing a fast reactor start-up, while the biofilm conserves its activity during a non-feeding period. The proposed hybrid reactor thus permits to treat both winery effluents and GSs.

Uptake and Bioaccumulation of Pentachlorophenol by Emergent Wetland Plant Phragmites australis (Common Reed) in Cadmium Co-contaminated Soil.

Despite many studies on phytoremediation of soils contaminated with either heavy metals or organics, little information is available on the effectiveness of phytoremediation of co-occurring metal and organic pollutants especially by using wetland species. Phragmites australis is a common wetland plant and its potential for phytoremediation of cadmium pentachlorophenol (Cd-PCP) co-contaminated soil was investigated. A greenhouse study was executed to elucidate the effects of Cd (0, 10, and 20 mg kg(-1)) without or with PCP (0, 50, and 250 mg kg(-1)) on the growth of the wetland plant P. australis and its uptake, accumulation and removal of pollutant from soils. After 75 days, plant biomass was significantly influenced by interaction of Cd and PCP and the effect of Cd on plant growth being stronger than that of PCP. Coexistence of PCP at low level lessened Cd toxicity to plants, resulting in improved plant growth and increased Cd accumulation in plant tissues. The dissipation of PCP in soils was significantly influenced by interactions of Cd, PCP and plant presence or absence. As an evaluation of soil biological activities after remediation soil enzyme was measured.

Sequential operation of a hybrid anaerobic reactor using a lignocellulosic biomass as biofilm support.

Agro-industries are facing many economic and environmental problems associated with seasonal generation of liquid and solid waste. In order to reduce treatment costs and to cope with seasonal variation, we have developed a hybrid anaerobic reactor operated sequentially by using lignocellulosic biomass (LB) as biofilm carrier support. Six LBs were tested to evaluate the treatment performance during a succession of two start-up periods, separated by a non-feeding period. After a short acclimation phase of several days, all the reactors succeeded in starting-up in less than 1month to reach an organic loading rate of 25gCODL(-1)d(-1). In addition, they restarted-up successfully in only 15days after a 3month non-feeding period, indicating that biofilms conserved their biological activities during this last phase. As a consequence, the use of LB as a biofilm support gives the potential to sustain seasonal variations of wastewater loads for industrial application.

Phytoremediation efficiency of a pcp-contaminated soil using four plant species as mono- and mixed cultures.

Bioremediation of soil polluted by pentachlorophenol (PCP) is of great importance due to the persistence and carcinogenic properties of PCP. Phytoremediation has long been recognized as a promising approach for removal of PCP from soil. The present study was conducted to investigate the capability of four plant species; white clover, ryegrass, alfalfa, and rapeseed grown alone and in combination to remediate pentachlorophenol contaminated soil. After 60 days cultivation, white clover, raygrass, alfalfa, and rapeseed all significantly enhanced the degradation of PCP in soils. Alfalfa showed highest efficiency for the removal of PCP in single cropping flowed by rapeseed and ryegrass. Mixed cropping significantly enhanced the remediation efficiencies as compared to single cropping; about 89.84% of PCP was removed by mixed cropping of rapeseed and alfalfa, and 72.01% of PCP by mixed cropping of rape and white clover. Mixed cropping of rapeseed with alfalfa was however far better for the remediation of soil PCP than single cropping. An evaluation of soil biological activities as a monitoring mechanism for the bioremediation process of a PCP-contaminated soil was made using measurements of microbial counts and dehydrogenase activity.

Does irrigation with reclaimed water significantly pollute shallow aquifer with nitrate and salinity? An assay in a perurban area in North Tunisia.

In Tunisia, reclaimed water is increasingly used for irrigation in order to mitigate water shortage. However, few studies have addressed the effect of such practice on the environment. Thus, we attempted in this paper to assess the impact of irrigation with reclaimed water on the nitrate content and salinity in the Nabeul shallow aquifer on the basis of satellite images and data from 53 sampled wells. Ordinary and indicator kriging were used to map the spatial variability of these groundwater chemical parameters and to locate the areas where water is suitable for drinking and irrigation. The results of this study have shown that reclaimed water is not an influential factor on groundwater contamination by nitrate and salinity. Cropping density is the main factor contributing to nitrate groundwater pollution, whereas salinity pollution is affected by a conjunction of factors such as seawater interaction and lithology. The predictive maps show that nitrate content in the groundwater ranges from 9.2 to 206 mg/L while the electric conductivity ranges from 2.2 to 8.5 dS/m. The high-nitrate concentration areas underlie sites with high annual crop density, whereas salinity decreases gradually moving away from the coastline. The probability maps reveal that almost the entire study area is unsuitable for drinking with regard to nitrate and salinity levels. Appropriate measures, such as the elaboration of codes of good agricultural practices and action programs, should be undertaken in order to prevent and/or remediate the contamination of the Nabeul shallow aquifer.

Evaluating the phytoremediation potential of Phragmites australis grown in pentachlorophenol and cadmium co-contaminated soils.

Pot-culture experiments were conducted to evaluate the phytoremediation potential of a wetland plant species, Phragmites australis in cadmium (Cd) and pentachlorophenol (PCP) co-contaminated soil under glasshouse conditions for 70 days. The treatments included Cd (0, 5 and 50 mg kg(-1)) without or with PCP (50 and 250 mg kg(-1)). The results showed that growth of P. australis was significantly influenced by interaction of Cd and PCP, decreasing with either Cd or PCP additions. Plant biomass was inhibited and reduced by the rate of 89 and 92% in the low and high Cd treatments and by 20 and 40% in the low and high PCP treatments compared to the control. The mixture of low Cd and low PCP lessened Cd toxicity to plants, resulting in improved plant growth (by 144%). Under the joint stress of the two contaminants, the ability of Cd uptake and translocation by P. australis was weak, and the BF and TF values were inferior to 1.0. A low proportion of the metal is found aboveground in comparison to roots, indicating a restriction on transport upwards and an excluding effect on Cd uptake. Thus, P. australis cannot be useful for phytoextraction. The removal rate of PCP increased significantly (70%) in planted soil. Significant positive correlations were found between the DHA and the removal of PCP in planted soils which implied that plant root exudates promote the rhizosphere microorganisms and enzyme activity, thereby improving biodegradation of PCP. Based on results, P. australis cannot be effective for phytoremediation of soil co-contaminated with Cd and PCP. Further, high levels of pollutant hamper and eventually inhibit plant growth. Therefore, developing supplementary methods (e.g. exploring the partnership of plant-microbe) for either enhancing (phytoextraction) or reducing the bioavailability of contaminants in the rhizosphere (phytostabilization) as well as plant growth promoting could significantly improve the process of phytoremediation in co-contaminated soil.

Phytoremediation potential of maize (Zea mays L.) in co-contaminated soils with pentachlorophenol and cadmium.

The ubiquitous coexistence of heavy metals and organic contaminants was increased in the polluted soil and phytoremediation as a remedial technology and management option is recommended to solve the problems of co-contamination. Growth of Zea mays L and pollutant removal ability may be influenced by interactions among mixed pollutants. Pot-culture experiments were conduced to investigate the single and interactive effect of cadmium (Cd) and pentachlorophenol (PCP) on growth of Zea mays L, PCP, and Cd removal from soil. Growth response of Zea mays L is considerably influenced by interaction of Cd and PCP, significantly declining with either Cd or PCP additions. The dissipation of PCP in soils was notably affected by interactions of Cd, PCP, and plant presence or absence. At the Pentachlorophenol in both planted and non-planted soil was greatly decreased at the end of the 10-week culture, accounting for 16-20% of initial extractable concentrations in non-planted soil and 9-14% in planted soil. With the increment of Cd level, residual pentachlorophenol in the planted soil tended to increase. The pentachlorophenol residual in the presence of high concentration of Cd was even higher in the planted soil than that in the non-planted soil.

Generalization and formalization of the US EPA procedure for design of treated wastewater aquifer recharge basins: II. Retrofit of Souhil Wadi (Nabeul, Tunisia) pilot plant.

The 'Cap Bon' peninsula in Tunisia suffers from intensive tourist activities, high demographic increase and industrial development. As groundwater had been for a long time the main water source, aquifers had been subject to a severe depletion and seawater intrusion. Despite the measures taken prohibiting new drillings and water carrying by the construction of a waterway linking the region to the north-west region of Tunisia, the problem of water shortage persists. Artificial recharge of groundwater with treated wastewater has been decided as a technique to replenish the region aquifers. A pilot plant was constructed in the early 1980s in Souhil Wadi (Nabeul) area. Many experiments have been carried out on this plant and have led to controversial opinions about its performance and its impact on groundwater contamination. This contribution concerns the application of the procedure that we developed from the generalization and the formalization of the United States Environmental Protection Agency (US EPA) methodology for the design of treated wastewater aquifer recharge basins. This upgrading procedure implemented in a spreadsheet, has been used to retrofit the Souhil Wadi facility in order to improve its performance. This method highlighted the importance of the safety factor to estimate wastewater infiltration rate from clean water permeability measurements. It has, also, demonstrated the discordance between the initial design parameters of Souhil Wadi facility and their current status as they have changed with time and the infiltration capacity of the basins has been affected by clogging. Indeed, it has been demonstrated that with the current state of clogging of the basins, the design infiltration rate limited by the most restrictive layer (6.1 cm/hr) corresponds to 22% of the surface infiltration rate reached after a drying period of 10 d, which means that we need more basins to absorb the daily loading rate. The design method leads to the construct ion of five basins of 961 m(2) (31 × 31 m) each, with one basin being flooded for 3 d with 27 cm of water daily and rested for 10 d. The current status is completely different as only four basins are constructed with 324 m(2) each. Many actions in the short, medium and long term have been advised in order to improve the system performance.

Generalization and formalization of the USEPA procedure for design of treated wastewater aquifer recharge basins: I. Theoretical development.

Groundwater is vulnerable to overdraft and depletion, especially in relatively dry regions where natural recharge rates are very low and groundwater is the main source of water. Artificial recharge of groundwater with treated wastewater has been widely adopted as a technique to replenish the overdraft aquifers. Indeed, in the USA, the technique has been practised for a long time. In 1981, a design procedure manual was developed for practitioners by the United States Environmental Protection Agency (USEPA). It was updated in 1984 and lastly in 2006. However, the design procedure has not been fully generalized for the different situations and has not been fully formalized in order to allow its automated implementation on calculation software (i.e. spreadsheet). Therefore, in this paper we formalized and generalized the USEPA design procedure to achieve an automated iterative method of calculation which can be easily implemented in a spreadsheet.

Characterization of ammonium retention processes onto cactus leaves fibers using FTIR, EDX and SEM analysis.

In order to reduce the impact of nitrogen pollution and to increase the agronomic value of plant wastes to be reused as organic fertilizer, we have investigated the removal of ammonium from aqueous solutions onto cactus leave fibers (CLF), and the mechanisms involved in the retention of ammonium at CLF surface. The results showed that ammonium retention onto these fibers occurred for a wide pH (6-10) and temperature ranges (20-60°C) and the biosorption potential of CLF increased with temperature from 1.4 to 2.3 mg g(-1) for initial concentration of 50 mg L(-1). The modeling studies showed that the ammonium biosorption was well described by the pseudo-second-order model, predicting therefore, chemisorption interactions-type at earlier stages and by intraparticle diffusion at later stages. Biosorption is governed by film diffusion process at higher concentrations and by particle diffusion process at higher temperatures. The surface of CLF determined by SEM revealed the presence of cracks and cavities which may allow the intraparticle diffusion and the ion exchange processes. Moreover, FTIR and EDX analysis before and after ammonium retention showed that the main mechanisms involved in the removal of ammonium were the ionic exchange by calcium ions as well as H(+) and the complexation with carboxylic, alcoholic and phenolic groups.