A novel heterotrophic-autotrophic denitrification (HAD) approach supported by mixing granulated spongy iron, methanol, and mixed bacteria was proposed for the remediation of nitrate-nitrogen (NO₃-N) contaminated groundwater in a dissolved oxygen (DO)-rich environment. The HAD process involves biological deoxygenation, chemical reduction (CR) of NO₃-N and DO, heterotrophic denitrification (HD), and autotrophic denitrification (AD). Batch experiments were performed to: (1) investigate deoxygenation capacities of HAD; (2) determine the contributions of AD, HD, and CR to the overall NO₃-N removal in the HAD; and (3) evaluate the effects of environmental parameters on the HAD. There were 174, 205, and 2,437 min needed to completely reduce DO by the HAD, spongy iron-based CR, and by the mixed bacteria, respectively. The HAD depended on abiotic and biotic effects to remove DO. CR played a dominant role in deoxygenation in the HAD. After 5 days, approximately 100, 63.0, 20.1, and 9.7 % of the initial NO₃-N was removed in the HAD, HD, AD + CR, and CR incubations, respectively. CR, HD, and AD all contributed to the overall NO₃-N removal in the HAD. HD was the most important NO₃-N degradation mechanism in the HAD. There existed symbiotic, synergistic, and promotive effects of CR, HD, and AD within the HAD. The decrease in NO₃-N and the production of nitrite-nitrogen (NO₂-N) and ammonium-nitrogen (NH₄-N) in the HAD were closely related to the C to N weight ratio. The C to N ratio of 3.75:1 was optimal for complete denitrification. Denitrification rate at 27.5°C was 1.36 times higher than at 15.0°C.

The upper limit of fluoride concentration in water for human consumption is 1.5 ppm. Many studies have been carried out concerning the water fluoride concentration in wide areas around the world, but none have studied the change of fluoride concentration as a function of geographical coordinates and through time. This paper describes ‘microvariation’ of fluoride concentration among wells separated by less than 500 m in a month. On the other hand, ‘macrovariation’ is also studied describing changes among cities that are separated by more than 10 km and compared with fluoride concentrations measured 65 years ago. Fluoride concentration was measured in a wide geographical area of Argentina, which is 133,000 km². Samples of water were collected from different regions. Macrovariation: Differences in fluoride concentration in well water among regions were found, as well as an increase in water fluoride concentration during seven decades. Microvariation: Daily water fluoride concentration in a specific area displayed a great variation in the measurements through time. In addition, wells with no more than 500 m of separation were measured at the same time and were significantly different. These results indicate that in order to determine the fluoride concentration of a region, different samples of the same area should be obtained and a sampling through time should also be done.

The impact of thermal pollution of leachate from a post-coal mine heap on three macrophyte species: Phragmites australis, Typha latifolia, and Scirpus sylvaticus was examined over the entire vegetation season. Hydrological measurements showed that the temperature of the leachate was ca 50 °C at the site of leachate inflow and decreased to ca 15 °C at the end of discharge canal. The annual temperature and conductivity of leachate from the two control sites, a polluted water stream in the vicinity of the waste tip and an unpolluted stream, differ significantly. However, only the temperature explained the differences in plant traits. In April, and in some cases in May, plants in the leachate were significantly higher than in those on the control sites in terms of biomass and plant height. Thermal pollution caused a phenological shift in all species and also caused Scirpus plants to die out more quickly. Temperature also affected the proportion flowering vs. vegetative individuals, e.g., none of Scirpus plants started to bloom.

Bacteria, actinomycetes, and fungi are the dominant components of the soil microflora, and some of their species can perform denitrification. The aim of this study was to investigate the interactions of three kinds of denitrifiers in mix-culturing systems. Three denitrifying strains, i.e., one bacterial strain (strain B5), one actinomycete strain (strain A2), and one fungal strain (strain F1), were isolated from a rice paddy soil. Denitrifier interactions were examined by analyzing the population dynamics and metabolic substance in the mix-culturing systems with two and three strains and by estimating the effects of cell-free culture filtrates on the strains. Results showed that the growth of B5 was enhanced by F1 and A2, respectively, and nitrate removal proportions in the culture systems increased from 52% (B5) to 64% (B5 + F1) and 67% (B5 + A2), and the nitrate removal was further enhanced in the three strain mix-culturing system (74%, A2 + F1 + B5). Strain B5 stimulated the cell growth of A2 directly and indirectly. The existence of A2 was lethal for cell growth of F1, while A2 was also suppressed by F1. The suppressive interaction reduced nitrate removal rates from the single systems of 12.8 (F1) and 11.5 mg L−1 day−1 (A2) to 8.75 mg L−1 day−1 (A2 + F1). Likewise, F1 was inhibited by B5. The results also showed that the cell-free culture filtrates of other strains suppressed the cell growth of B5 and F1, respectively, but enhanced the cell growth of A2. In addition to the direct effect of cell-free culture filtrates, other indirect relationships could affect the denitrifier spatial distributions and balance of the suppression or promotion effects, which were beneficial to maintain the microbial structure and function stability with a low nitrous oxide emission in the soil.

Animal wastes are commonly used in a sustainable manner to fertilize crops. However, manures contain numerous pathogenic bacteria that can impact animal and human health. Treatment of animal waste by anaerobic digestion has the potential to reduce pathogen loading to land. This study was conducted to determine the fate of bacteria applied in raw and anaerobically digested dairy slurries that were broadcast and subsurface applied in a field of forage grasses. Digested slurry had significantly fewer indicator bacteria, Escherichia coli and fecal coliform at time of application. Anaerobic digestion did not increase the survivability of indicator bacteria. Waste treatment and application method did not affect the rate of bacteria die-off. There were fewer E. coli and fecal coliform at the end of each trial in the soils that received digested slurry. Anaerobic digestion of dairy waste has the potential to reduce pathogenic bacteria loading to cropland.

Since swine wastewater is used by farmers for soil fertilization, evaluation of toxic compounds or micro-contaminants of separate streams is required. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological characterization of swine wastewater. To distinguish the most important toxic compounds, a physicochemical characterization and phase I-TIE procedure were performed. The acute toxic effect of swine wastewater and treated fractions (phase II-TIE) were evaluated using Daphnia magna determining 48-h LC50. Results show a high level of conductivity (23.5 μS cm−1), which is explained as due to the concentration of ions, such as ammonium (NH 4 + –N 1.6 g L−1), sulfate (SO 4 2− 397.3 mg L−1), and chlorine (Cl− 1,230.0 mg L−1). The acute toxicity of the swine wastewater was evaluated on D. magna (48-h LC50 = 3.4%). Results of the different water treatments indicate that anionic exchange treatments could reduce 22.5% of swine wastewater’s acute toxicity by reducing chlorine (to around 51%) and conductivity (8.5%). On the other hand, cationic exchange treatment increased acute toxicity on D. magna (% RT = −624.4%), by reducing NH 4 + –N (around 100%) and total nitrogen (95.5%). This finding suggests that part of the toxicity comes from anionic compounds, such as chlorine.

Lead (Pb) is known as an important aquatic contaminant with different toxic effects on various organisms. Until now, only few quantitative investigations have been published comparing Pb content in different organs of adult freshwater crabs. Their capacity to bioaccumulate other heavy metals is already known, and they can potentially transfer Pb to the terrestrial systems, as they are frequent trophic items of reptiles and birds, even humans. The objectives of this study were to assess Pb accumulation in the gills, carapace, digestive gland, and quela muscle of the freshwater crab Zilchiopsis oronensis, and to correlate bioaccumulation with morphometric data and sex. The crabs were manually caught in unpolluted ponds of the middle Paraná River alluvial valley (Santa Fe, Argentina). After the acclimation period, they were individually and randomly exposed per quadruplicate to three Pb experimental doses: 20, 40, and 80 mg Pb/L, in plastic cages during 15 days. After dissecting the crabs, the tissues were analyzed for lead in a Perkin Elmer Analyst 800 atomic absorption spectrometer. We found significant differences (p < 0.05) between the control and each one of the treatments but not between treatments (p > 0.05) and highly significant differences (p < 0.0001) between Pb concentration in organs. The Tukey posttest showed significant differences (p < 0.05) between gills–carapace, gills–digestive gland, and gills–quela muscle. The weight of the crabs only showed a negative correlation with Pb in the quela muscle (r = −0.53; p = 0.03). Pb in the carapace (but not in the other tissues) was positively correlated with the width (p = 0.571) and length (p = 0.616). Males accumulated more Pb than females, though not significantly. The present paper is aimed to contribute to our knowledge on Pb accumulation in freshwater crabs and select the better indicator organisms for biomonitoring.

A Gram-negative bacterium strain LWD09, capable of growing aerobically on 3,4-dichloroaniline (DCA) as the sole carbon and energy source, was isolated from the farm field. This bacterium was identified as Myroides odoratimimus strain by morphological, physiological, and biochemical characteristics as well as 16S rDNA sequence. Analysis of culture pH, temperature, cells growth, and DCA concentration demonstrated that strain LWD09 could effectively degrade DCA without a lag phase. The kinetics of DCA degradation was well described using the Andrews equation, and the kinetic parameters were as follows: q max = 1.74 h−1, K s = 43.5 mg L−1, and K i = 230.3 mg L−1. In addition, strain LWD09 was found to be moderately halophilic and showed the highest power of DCA degradation in 5% NaCl (w/w, %). With initial concentrations of 30, 100, and 200 mg L−1, 100%, 80.4%, and 33.2% of DCA were transformed after 96 h in 5% NaCl, respectively. These results suggest that strain LWD09 has the potential to degrade DCA in saline wastewater. To date, this is the first report on the degradation of DCA by a M. odoratimimus strain with moderate salinity tolerance.

The main objective of this study was to examine the effect of an electro-Fenton pretreatment on the biodegradability of sulfamethazine-polluted solutions. The aim of the pretreatment was only to degrade this molecule in order to increase the biodegradability of the effluent and therefore allow a subsequent biological treatment. Preliminary tests showed the absence of biodegradability of the target compound. The degradation of sulfamethazine by electro-Fenton process was then examined using a carbon felt cathode and a platinum anode in an electrochemical reactor containing 1 L of solution. The influence of some experimental parameters such as initial concentration, temperature and current intensity on the degradation by electro-Fenton step has been investigated. In addition, the biodegradability of the solution after electrochemical pretreatment was examined and showed a Biological Oxygen Demand (BOD5) on Chemical Oxygen Demand (COD) ratio above the limit of biodegradability, namely 0.4, for several experimental conditions. The feasibility of coupling an electro-Fenton pretreatment with a biological degradation of by-products in order to mineralize polluted solutions of sulfamethazine was confirmed.

The biomass characteristics, the process performance, and the microbial community for a sequencing batch reactor (SBR) and a submerged membrane SBR (MSBR) were evaluated. A synthetic wastewater containing only 4-chlorophenol (4CP) was used as the sole source of carbon and energy. Degradation efficiencies of 4CP were higher than 99% for both reactors, and no significant differences on the 4CP degradation rates were observed for the SBR (116.9 ± 0.9 mg 4CP g VSS−1 h−1) as well as for the MSBR (117.3 ± 0.5 mg 4CP g VSS−1 h−1). Despite the similar results obtained for the physicochemical parameters, it was found that the biomass characteristics were different considering the sludge volumetric index, settling velocity, protein content in the mixer liquor, and total suspended solids in the effluent. The settling velocity was three times higher in the SBR than in the MSBR; however, a better quality, considering suspended solids, was observed for the MSBR. The protein concentration in the mixed liquor was higher in the MSBR than in the SBR, generating foaming problems in the MSBR. A similarity analysis was made with the Ochiai–Barkman index. Even though the reactors were inoculated with the same biomass, significant differences in the composition and populations dynamics were observed.