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.

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.

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.

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.

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 (SSVF_p + SSHF). (2) A reed-Phragmites australis SSVF bed partially saturated at 40% of its depth (SSVF_PS); (3) A cattail-Typha angustofolia SSVF bed partially saturated at 40% of its depth (SSVF_TS). 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 SSVF_TS 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, SSVF_P 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 SSVF_ST (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 SSVF_ST in the presence of Thypha angustofolia have favored the development of ANAMMOX activity in comparison to the other configurations.

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.

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.

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.

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.

Effect of temperature and pH on the biosorption of ammonium onto Posidonia oceanica fibers: equilibrium, and kinetic modeling studies

In the present study, the effects of temperature and pH on ammonium biosorption onto Posidonia oceanica fibers were investigated. The results showed that the ammonium biosorption onto these fibers occurred for a wide pH range and the adsorption capacity of these fibers increased with increasing temperature. 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 intraparticle diffusion at later stages. The ammonium biosorption was governed by film diffusion process at various temperatures. Besides, equilibrium data were very well represented by Langmuir isotherm, which confirmed the mono-layer coverage. The use of P. oceanica fibers presents an interesting option for both tertiary wastewater treatment (as a possible non-conventional biosorbent for the removal of ammonium), and waste recycling (as a fertilizer and compost).

Exploitation of biological wastes for the production of value-added hydrolases by Streptomyces sp. MSWC1 isolated from municipal solid waste compost

Actinomycetes with the ability to degrade natural polysaccharides were isolated during a screening programme from soil, farmyard manure and municipal solid waste compost. One of the most potent isolates was identified as Streptomyces sp. MSWC1 using morphological and biochemical properties along with 16S rDNA partial sequence analysis. The highest enzyme production by Streptomyces was observed for the xylanase and chitinase activity on different carbon sources with an optimum of 12,100 IU ml(-1) and 110 IU ml(-1) at 3 days' culture on 1% of xylan and chitin, respectively. To meet the demand of industry, low-cost medium is required for the production of hydrolases by Streptomyces sp. Strain MSWC1 grown on manure, compost, and a natural carbon source was used to evaluate the re-utilisation of biological wastes for the production of value-added products. Despite the presence of a high amount of toxic heavy metals in the compost, Streptomyces produced interesting enzymes that have been biochemically characterized.

Ammonium biosorption onto sawdust: FTIR analysis, kinetics and adsorption isotherms modeling

Sawdust, an available and renewable biomass, was investigated as a novel ammonium biosorbent. Biosorption occurred over a pH range of 6-10, reached an equilibrium state within only 20 min, and can be described by a pseudo-second-order model predicting a chemisorption process. Equilibrium data were very well represented by Langmuir isotherm and confirm monolayer coverage. FTIR analysis before and after biosorption of ammonium onto sawdust suggested that the main mechanisms involved in the removal of ammonium might be the ionic exchange and complexation. The use of sawdust presents an interesting option for both tertiary wastewater treatment (as a possible non-conventional biosorbent for the removal of ammonium), and waste recycling (as a fertilizer and compost).

Effect of municipal solid waste compost and sewage sludge use on wheat (Triticum durum): growth, heavy metal accumulation, and antioxidant activity

BACKGROUND

Inappropriate utilisation of biosolids may adversely impact agrosystem productivity. Here, we address the response of wheat (Triticum durum) to different doses (0, 40, 100, 200 and 300 t ha(-1)) of either municipal solid waste (MSW) compost or sewage sludge in a greenhouse pot experiment. Plant growth, heavy metal uptake, and antioxidant activity were considered.

RESULTS

Biomass production of treated plants was significantly enhanced at 40 t ha(-1) and 100 t ha(-1) of MSW compost (+48% and +78% relative to the control, respectively). At the same doses of sewage sludge, the increase was only 18%. Higher doses of both biosolids restricted significantly the plant growth, in concomitance with the significant accumulation of heavy metals (Ni2+, Pb2+, Cu2+ and Zn2+), especially in leaves. Leaf activities of antioxidant enzymes (ascorbate peroxidase, glutathione reductase, catalase and superoxide dismutase) were unchanged at 40 t ha(-1) MSW compost or sewage sludge, but were significantly stimulated at higher doses (200-300 t ha(-1)), together with higher leaf concentration of reduced glutathione.

CONCLUSION

This preliminary study suggests that a MSW supply at moderate doses (100 t ha(-1)) could be highly beneficial for wheat productivity.

Accumulation and fractionation of trace metals in a Tunisian calcareous soil amended with farmyard manure and municipal solid waste compost

A field plots experiment was carried out to assess the effects of repeated application of municipal solid waste compost in comparison to farmyard manure on the accumulation and distribution of trace metals, as well as organic carbon and nitrogen in Tunisian calcareous soil. Compared with untreated soil, the application of the two organic amendments significantly increased the organic carbon and nitrogen contents of the soil. Particle-size fractionations showed that carbon and nitrogen were mainly found to occur in the macro-organic matter fraction (80%). The two organic amendments significantly increased organic carbon in the macro-organic and mineral >150 microm fraction and the 150-50 microm fraction, as well as the organic nitrogen in 150-50 microm and macro-organic fraction. Compared with farmyard manure, municipal solid waste compost significantly increased total Cd, Cu, Pb and Zn contents in the topsoil. These trace metals were mainly present in the macro-organic matter fraction. Significant increases of Cu, Zn and Pb were detected in the 150-50 microm, <50 microm and macro-organic fractions after application of municipal solid waste compost. A significant increase of Cd content was only observed in the 150-50 microm fraction. The trace metals also showed different fractionation patterns when the BCR sequential extraction scheme was applied on untreated and compost-treated soil. The residual fraction was found to be the major fraction, especially for Cu, Cr, Ni and Zn. In contrast, Cd was mainly present in the acid-extractable and reducible fraction, whereas Pb was mainly associated with the reducible fraction.

Dynamic sorption of ammonium by sandy soil in fixed bed columns: Evaluation of equilibrium and non-equilibrium transport processes

The release of excess nitrogen-containing compounds into groundwater is a major concern in aquifer recharge by the Soil Aquifer Treatment (SAT) process. Ammonium (NH(4)(+)) is one of the most nocive and common nitrogen compounds in wastewaters. In order to assess the risk of wastewater use for aquifer recharge, NH(4)(+)adsorption onto Souhil wadi soil sampled from the SAT pilot plant (Nabeul, Tunisia) was studied using laboratory columns experiments. Several experiments were conducted using aqueous synthetic solutions under different aqueous ammonium concentrations and flow rates. Furthermore, a real wastewater solution was used to test the effect of competitive cations contents on NH(4)(+) adsorption. Afterwards, the Hydrus-1D model was used in inverse mode to simulate the ammonium transport through the Souhil wadi soil. For the synthetic solutions, the adsorbed ammonium amount varied from 1 to 30.7 mg kg(-1) for aqueous ammonium concentrations between 4.9 and 36.4 mg L(-1). The linear isotherm model was found to be the most suitable for describing this adsorption. The flow rate decrease from 45 to 15 mL min(-1) induced an increase in the ammonium adsorption capacity by 49%. Indeed, the lesser the flow rate is, the longer the residence time and the higher the exchange between the aqueous solution and soil matrix. The use of wastewater instead of aqueous synthetic solution decreased about 7 times the Souhil wadi adsorption capacity of ammonium because of its relatively high concentrations of competitive ions such as calcium and magnesium. The use of the Hydrus-1D model showed that the chemical non-equilibrium model was the best to simulate the ammonium transport through the laboratory soil columns.

Effectiveness of compost use in salt-affected soil

Soil degradation and salinization are two of the utmost threat affecting agricultural areas, derived from the increasing use of low quality water and inappropriate cultural practices. The problem of low productivity of saline soils may be ascribed not only to their salt toxicity or damage caused by excess amounts of soluble salts but also arising from the lack of organic matter and available mineral nutrients especially N, P, and K. Concerns about salinization risk and environmental quality and productivity of agro-ecosystems have emphasized the need to develop management practices that maintain soil resources. Composted municipal solid waste (MSW) was commonly used to enhance soil productivity in the agricultural lands and rebuild fertility. However, their application could be also a promising alternative to alleviate the adverse effects caused by soil salinization. MSW compost, with high organic matter content and low concentrations of inorganic and organic pollutants allow an improvement of physical, chemical and biochemical characteristics and constitute low cost soil recovery.

Study of the effects of urban organic residues on the distribution of culturable actinomycetes in a Tunisian agricultural soil

The main objective of this investigation was to identify a collection of actinomycetes isolates and to study the influence of amendment [municipal solid waste compost (MSWC) and farmyard manure (FM)] on their distribution in agricultural soil. For this purpose, a phenotypic and molecular characterization of 226 isolates collected from soil (with and without amendment) and 55 isolates from MSWC and FM was developed. The phenotypic study showed that the majority of strains isolated belong to the genus Streptomyces. By using the 16S rDNA polymerase chain reaction-restriction fragment length polymorphism method (restriction digest using six enzymes AluI, HhaI, MspI, TaqI, RsaI and HaeIII), two clusters were found: Streptomyces, dominant genus and Amycolatopsis, followed by Nocardioides. This result agreed with phylogeny revealed by 16S rDNA sequencing. The number of these actinomycetes in soil increased with FM or MSWC application. The studied soil is a potential source for isolation of actinomycetes, especially Streptomyces, and the application of organic amendment to the soil appeared to have an impact on the diversity of actinomycetes. Amendment of the soil with MSWC and FM significantly increased the number of actinomycetes due to the contribution of bacteria originally contained in biowastes and/or by stimulation of the endogenous soil micro-organisms.

Microbiological parameters and maturity degree during composting of Posidonia oceanica residues mixed with vegetable wastes in semi-arid pedo-climatic condition

The aim of this study was to characterize the biological stability and maturity degree of compost during a controlled pile-composting trial of mixed vegetable residues (VR) collected from markets of Tunis City with residues of Posidonia oceanica (PoR), collected from Tunis beaches. The accumulation in beaches (as well as their removal) constitutes a serious environmental problem in all Mediterranean countries particularly in Tunisia. Aerobic-thermophilic composting is the most reasonable way to profit highly-valuable content of organic matter in these wastes for agricultural purposes. The physical, chemical, and biological parameters were monitored during composting over 150 d. The most appropriate parameters were selected to establish the maturity degree. The main result of this research was the deduction of the following maturity criterion: (a) C/N ratio < 15; (b) NH4+-N < 400 mg/kg; (c) CO2-C < 2000 mg CO2-C/kg; (d) dehydrogenase activity < 1 mg TPF/g dry matter; (e) germination index (GI) > 80%. These five parameters, considered jointly are indicative of a high maturity degree and thus of a high-quality organic amendment which employed in a rational way, may improve soil fertility and soil quality. The mature compost was relatively rich in N (13.0 g/kg), P (4.74 g/kg) and MgO (15.80 g/kg). Thus composting definitively constitutes the most optimal option to exploit these wastes.

Contrasting effects of municipal compost on alfalfa growth in clay and in sandy soils: N, P, K, content and heavy metal toxicity

The limits for loading soils with Tunisian urban compost for cultivating Medicago sativa were determined in a 6-month experiment in a greenhouse. Mature municipal solid waste compost (MSWC) from Tunis city was applied to clay and sandy soils from cultivated fields at rates equivalent to 40, 80, 120tha(-1). In the absence of MSWC, the shoot biomass (dry weight) cumulated over four cuts was 2-2.5 lower in sandy soil than in clay soil. It was 20-25% augmented upon MSWC addition in clay soil, independently of MSWC dose. The opposite trend was observed in sandy soil, the shoot yields being diminished by MSWC in a dose dependent manner. In MSWC-amended clay soil but not in sandy soil, Cd, Cu, Zn, and Pb concentrations in shoots remained below or close to the tolerated values according to EEC norms. The MSWC might be used as conditioner for clay soil, but not for sandy soil.

Application of municipal solid waste compost reduces the negative effects of saline water in Hordeum maritimum L

The efficiency of composted municipal solid wastes (MSW) to reduce the adverse effects of salinity was investigated in Hordeum maritimum under greenhouse conditions. Plants were cultivated in pots filled with soil added with 0 and 40tha(-1) of MSW compost, and irrigated twice a week with tap water at two salinities (0 and 4gl(-1) NaCl). Harvests were achieved at 70 (shoots) and 130 (shoots and roots) days after sowing. At each cutting, dry weight (DW), NPK nutrition, chlorophyll, leaf protein content, Rubisco (ribulose-bisphosphate carboxylase/oxygenase) capacity, and contents of potential toxic elements were determined. Results showed that compost supply increased significantly the biomass production of non salt-treated plants (+80%). This was associated with higher N and P uptake in both shoots (+61% and +80%, respectively) and roots (+48% and +25%, respectively), while lesser impact was observed for K+. In addition, chlorophyll and protein contents as well as Rubisco capacity were significantly improved by the organic amendment. MSW compost mitigated the deleterious effect of salt stress on the plant growth, partly due to improved chlorophyll and protein contents and Rubisco capacity (-15%, -27% and -14%, respectively, in combined treatment, against -45%, -84% and -25%, respectively, in salt-stressed plants without compost addition), which presumably favoured photosynthesis and alleviated salt affect on biomass production by 21%. In addition, plants grown on amended soil showed a general improvement in their heavy metals contents Cu2+, Pb2+, Cd2+, and Zn2+ (in combined treatment: 190%, 53%, 168% and 174% in shoots and 183%, 42%, 42% and 114% in roots, respectively) but remained lower than phytotoxic values. Taken together, these findings suggest that municipal waste compost may be safely applied to salt-affected soils without adverse effects on plant physiology.

Solid-phase bioassays and soil microbial activities to evaluate PAH-spiked soil ecotoxicity after a long-term bioremediation process simulating landfarming

The residual ecotoxicity of long-term bioremediated soils concomitantly spiked with three PAHs at four levels (15, 75, 150, 300 mg Sigma 3 PAHs kg(-1) soil) was evaluated using physico-chemical analyses, solid-phase bioassays and soil microbial activities. The pot-scale bioremediation process consisted of weekly moderate waterings in the presence or absence of sewage sludge compost (SSC) under greenhouse conditions. After 15 months, anthracene and pyrene were almost completely degraded whereas benzo[a]pyrene was still persisting, most apparently in SSC-amended soil treatments. However, no apparent toxic effects of the residual PAHs could be detected. SSC application at 40 t ha(-1) was performed to valorize the biowaste and stimulate PAH biodegradation but caused soil salinization and pH reduction at the end of the bioremediation process. Consequently, SSC-amended soils were characterized by strong phytotoxicity to lettuce and had adverse effects on the ostracod Heterocypris incongruens. Despite the smaller number of culturable bacterial populations in SSC-amended soils, soil enzymatic activities were not affected by the organic amendment and residual PAHs; and the bioremediation efficiency was likely to be more limited by the bioavailability of PAHs rather than by the total number of PAH-degraders.

Effects of municipal solid waste compost application on the microbial biomass of cultivated and non-cultivated soil in a semi-arid zone

The aim of this study was to assess whether soil microbial biomass could be used as an indicator of environmental changes following the application of organic residue (compost of municipal solid waste and farmyard manure) or mineral fertilizers (N and P) into cultivated or uncultivated loam-clayey soil, for three consecutive years. The carbon and nitrogen of the microbial biomass (B(C) and B(N) were studied using the fumigation-extraction method. For the two cultivated and uncultivated plots, B(N) and B(C) were more important in the superficial profile (0-20 cm) than in the deep one (20-40 cm). In the uncultivated soil, we observed a good linear relation between B(C) and B(N) at the level of upper soil horizon during the wet season with r coefficients of 0.95, 0.71 and 0.80 for the consecutive years 2000, 2001 and 2002, respectively. Microbial biomasses C and N increased during the rainy season and decreased during the dry season. Microbial biomass C and N showed the higher content with compost and farmyard manure at 40 tonnes ha(-1). Moreover, the results showed that at the beginning of the experiment, the microbial biomass was higher in the ploughed wheat-cultivated plot than in the uncultivated one. Microbial biomass C and N in the cultivated plot amended with compost at 40 tonnes ha(-1) were significantly different in comparison with the soil microbial biomass amended with farmyard manure. The combining of chemical fertilizer with the organic fertilizer, such as compost at 40 or 80 tonnes ha(-1) and farmyard manure, increased the microbial biomasses C and N after 1 and 2 years. In the cultivated or uncultivated plots the results revealed that the best application rate of the compost was 40 tonnes ha(-1) and when the compost rate was increased from 40 to 80 tonnes ha(-1) both B(C) and B(N) decreased significantly.

Microbial C and N dynamics during composting process of urban solid waste

Microbial characterization of composting is of importance for the optimization of the process and the quality of the end product. The aim of this work was to follow microbial biomass C and N dynamics during the composting process of urban solid waste. Microbial biomass C (B(C)) ranged from 4.06 to 1 microg kg(-1) of dry compost from day 5 to day 62 and decreased to reach 0.44 mg kg(-1) in mature compost. Microbial biomass N (B(N)) showed the same trend as B(C), ranging from 1.472 to 0.443 microg kg(-1) of dry compost from day 5 to day 62. This behaviour is probably related to the decreasing availability of readily decomposable substrates with the ongoing of the process. B(C) and B(N) showed a strong correlation (r = 0.78). The dynamics of the B(C)/B(N) ratio, index of the chemical composition of the whole microbial population suggested a shift in the composition of microbial populations during the process from prevailing bacteria and actinomycetes to prevailing fungi.

Effects of anthracene, pyrene and benzo[a]pyrene spiking and sewage sludge compost amendment on soil ecotoxicity during a bioremediation process

The fate of spiked anthracene, pyrene and benzo[a]pyrene in soil with or without sewage sludge compost was assessed during a 6-month bioremediation process simulating landfarming. Bioassays and physico-chemical analyses were employed to monitor toxicity change in soil samples and elutriates through ten sampling campaigns. Pearson product-moment correlation coefficient was determined to measure the strength of relationship between bioassays and physico-chemical analyses. The PAH dissipation in soil was enhanced after the first water addition, and the remaining amounts at the end of the experiment were positively correlated to the number of benzene rings and the presence of sewage sludge compost. Toxicity of soil elutriates to Daphnia magna was evident at early stages, originating exclusively from sewage sludge compost amendment. The lettuce root elongation was continuously inhibited by elutriates for all the treatments including control soil, probably due to high salinity or to unaddressed leachable phytotoxic compounds that were present in the experimental soil. The newly developed direct solid-phase chronic toxicity test using ostracod (Heterocypris incongruens) succeeded in evaluating the soil-bound PAH toxicity, as PAHs could not be detected in elutriates.

Microbial biomass in a soil amended with different types of organic wastes

Application of different types of organic wastes may have a marked effect on soil microbial biomass and its activity. The objective of this study was to quantify the amount of microbial biomass in a loamy-clayey soil, amended with different types of organic waste residues (composts of municipal solid waste of different ages, sewage sludge and farmyard manure) and incubated for 8 weeks at 25 degrees C and two-thirds of field capacity, using the fumigation-extraction method. Both microbial biomass-C and -N (BC and BN, respectively) appeared to be dependent on the type of organic waste residues, on their degree of stability, and on their chemical characteristics. In general, organic wastes increased the microbial biomass-C content in the soil and the microbial BC was positively correlated with the organic C content, the C/N, neutral detergent fibre/N (NDF/N) and acid detergent fibre/N (ADF/ N) ratios. The microbial biomass content decreased according to the period of incubation, especially when the compost used was immature. The microbial biomass-N was positively correlated with the total N and percentage of hemicellulose. The microbial biomass-C was linearly related with the microbial biomass-N and the ratio BC/BN was exponentially related with the BC.

Magnetic susceptibility variation of MSW compost-amended soils: in-situ method for monitoring heavy metal contamination

Magnetic susceptibility was measured for agricultural soils in Mornag area, Tunisia, where the soils were partly amended by manure or compost obtained from municipal solid waste stabilisation ('MSW compost'). Our study indicates that natural non-treated soils and manure-amended soils are always low in magnetic susceptibility, but MSW compost-amended soils show higher values of this parameter. Actually, the increase of magnetic susceptibility shows a direct correspondence with the increasing of the amount of MSW compost added to the soil. According to the magnetic mineralogical investigation carried out by isothermal remanent magnetisation acquisition technique, higher magnetic susceptibility values are depending on an increase in ferromagnetic components such as either magnetite (beta-Fe3O4) or maghemite (gamma-Fe2O3) particles. The growth in content of these ferromagnetic components corresponds to an increase of the concentration of heavy metals in soils, which means that magnetic susceptibility indirectly indicates the concentration of heavy metals in MSW compost-amended soils.

Microbial characterization during composting of municipal solid waste

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60-55 degrees C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2 x 10(7) to 3.1 x 10(3) and 10(7) to 1.5 x 10(3) cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5 x 10(6) to 2.6 x 10(3) cells/g WDW and mesophilic bacteria were reduced from 5.8 x 10(9) to 1.8 x 10(7) bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60 degrees C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.

[Isolation of salmonella in wastewaters and study of indicator bacteria survival in soils]

Detection of salmonella in wastewaters was done in semi-industrial pilot plant. In parallel, survival of indicator bacteria (feacal coliforms and feacal streptococci) in the soil was evaluated into a laboratory incubation device. Results revealed the isolation of 21 strains of salmonella in 7 campaigns of analysis on DCLS media, and 6 strains on lactose-green-brilliant and phenol red media in 2 campaigns. Salmonella were recovered in all the lines of wastewater treatment. The study led on the survival of coliforms and streptococci bacteria allowed the conclusion that feacal streptococci introduced by wastewaters were more qualified to survive in the soil than feacal coliforms. On the other hand, feacal coliforms appeared more sensitive to the biological factors of the soil than feacal streptococci. The ambient temperature of incubation situated between 12 and 24 degrees C seemed suitable for bacteria survival in the soils.

[Hygienic aspects of aerobic fermentation of urban waste in the Tunisian context]

The use of the aerobic fermentation (composting) as an alternative of the landfilling of the municipal solid wastes was studied in a pilot plant in the District of Tunis. The effectiveness of the composting, by the windrow turning technical, in producing sanitized compost was considered. Fecal coliforms, fecal streptococcis and E. coli were used as an indicator organism. In addition, the evolution of the process was monitored using sporogenous bacteria. Under the experimental conditions, approximately five logarithmic unit reduction of fecal indicators was noted after a 60 days composting.

[Value of waste water in agriculture. Evaluation of soil bacterial contamination, water table and plant culture]

The present study aim was to valorize the treated waste water as source of fertilizers for vegetables seed production and to assess the eventual bacteriological contamination risks of soil, plant and phreatic ground water table. The bacteriological analysis of drained water did not reveal any fecal coliforms vertical migration in depth and a low fecal contamination (thermotolerant coliforms) is limited to the levels of superficial horizons. The seed produced by using waste water showed a slightly fecal contamination which disappeared following treatment with a (5% chloride solution. The treated waste water improve the onion seeds production per hectare in spite of the increases of the phytopathogenic hazards.

[Cytotoxicity of ferric chloride used as an adjuvant of organic acid precipitation]

The objective of this study was the amelioration of the organic acid precipitation technique currently used as a secondary stage for viruses concentration using ferric chloride (FeCl3) as an adjuvant. To carry out this work successfully, we have studied the cytotoxicity effect of FeCl3 towards cell lines usually used for the investigation of enteric viruses. Two kinds of african green monkey kidney cells, MA104 and BGM, were used as a cellular model. The results showed that optimum concentration of FeCl3 for either BGM or MA104 cell survival and organic acid precipitation varies from 0.5 to 1 mM. The cytotoxicity test used in this work was simple, easy to realize and gives an appreciable information about the cytotoxicity dose of a given biological and chemical product.

[A method for recovery of enteroviruses from milk]

A method of detection of enteric viruses in milk was studied. The high protein content of milk and the protein nature of enterovirus allowed the detection of these viruses using the organic acid flocculation method. The poliovirus type 1 (Mahoney strains) and the E.C.H.O.1 isolated from the environment were used as virus model and were inoculated to creamed, half-creamed and whole UHT commercialized milk. The method consists on a milk sample clarification with acid precipitation and centrifugation. The clarified extract is reduced to a final volume of 10 to 15 ml after addition of beef extract powder and protein precipitation. This technique allows the recovery of 26 to 36% of poliovirus type 1 and 10 to 46% of E.C.H.O.1 viruses. In this work, the ferric chloride (FeCl3), added in 0.5 to 1 mM final concentration, was used as an adjuvant for the organic acid precipitation.