Bayesian inference of physicochemical quality elements of tropical lagoon Nokoué (Benin).

In view of the very strong degradation of aquatic ecosystems, it is urgent to set up monitoring systems that are best able to report on the effects of the stresses they undergo. This is particularly true in developing countries, where specific and relevant quality standards and funding for monitoring programs are lacking. The objective of this study was to make a relevant and objective choice of physicochemical parameters informative of the main stressors occurring on African lakes and to identify their alteration thresholds. Based on statistical analyses of the relationship between several driving forces and the physicochemical parameters of the Nokoué lagoon, relevant physicochemical parameters were selected for its monitoring. An innovative method based on Bayesian statistical modeling was used. Eleven physicochemical parameters were selected for their response to at least one stressor and their threshold quality standards also established: Total Phosphorus (<4.5mg/L), Orthophosphates (<0.2mg/L), Nitrates (<0.5 mg/L), TKN (<1.85 mg/L), Dry Organic Matter (<5 mg/L), Dissolved Oxygen (>4 mg/L), BOD (<11.6 mg/L), Salinity (7.6 ‰), Water Temperature (<28.7 °C), pH (>6.2), and Transparency (>0.9 m). According to the System for the Evaluation of Coastal Water Quality, these thresholds correspond to "good to medium" suitability classes, except for total phosphorus. One of the original features of this study is the use of the bounds of the credibility interval of the fixed-effect coefficients as local weathering standards for the characterization of the physicochemical status of this anthropized African ecosystem.

Assessment of the quality of effluent management from university hospitals in the Littoral department in Benin.

BACKGROUND: Liquid discharges from hospitals (effluents) threaten the environment and are now a central concern of all stakeholders in the health system and those in the protection of the environment. The management of effluents is a major problem in developing countries. The objective of this study was to assess the quality of effluent management at the level of university hospital centers (CHU) in the Littoral region in Benin. METHODS: It was a cross-sectional, descriptive, evaluative study that took place in 2020 to assess the "structure", "process" and "results" components according to standard thresholds (Bad: < 60%; Acceptable: [60-80% [and Good: ≥ 80%). RESULTS: In all the CHUs, all the components, as well as the overall quality of the management of hospital effluents, had a score between 0 and 60%, with an assessment deemed bad. The poor quality of the process highlighted the non-compliance with standards relating to the management of hospital liquid discharges. Several factors linked to the "structure", "process" and "results" components at the same time explain this poor management of university hospitals effluents. CONCLUSION: These effluents discharged without prior treatment into wastewater could constitute a source of dissemination of potentially pathogenic microorganisms. It is therefore important to develop methods for treating these effluents before they are released into the natural environment.

Rare earth and precious elements in the urban sewage sludge and lake surface sediments under anthropogenic influence in the Republic of Benin.

Nowadays, sewage sludge and water bodies are subjected to heavy pollution due to rapid population growth and urbanization. Heavy metal pollution represents one of the main challenges threatening our environment and the ecosystem. The present work aims to evaluate the contamination state of the sewage sludge and lake sediments in the Republic of Benin. Twenty metallic elements including 15 rare earth elements (Eu, Sb, Cs, Nd, Pr, Gd, La, Ce, Tb, Sm, Dy, Ho, Eu, Yb, and Lu) and five precious elements (Ag, Au, Pd, Pt, and Ru) were investigated using inductive plasma-mass spectrometry. Results showed broad range concentrations of the elements. Ce, La, and Nd were present in both sediments and sewage sludge at concentrations ranging 5.80-41.30 mg/kg dry matter (DM), 3.23-15.60 mg/kg DM, and 2.74-19.26 mg/kg DM, respectively. Pr, Sm, Gd, Tb, Dy, Eu, Er, Yb, Cs, Ho, and Tm concentrations were lower (0.02-5.94 mg/kg DM). Among precious elements, Ag was detected at the highest concentration in all sites (0.43-4.72 mg/kg DM), followed by Pd (0.20-0.57 mg/kg DM) and Au (0.01-0.57 mg/kg DM). Ru and Pt concentrations were < 0.20 mg/kg DM in all samples. Pollution indices and enrichment factor indicated a strong to severe enrichment of the elements, mainly Ce and precious elements in both sediments and sewage sludge. This revealed a growing anthropogenic input which was also implied by principal component analysis. The evaluation of pollution loading index (PLI) indicated a moderate to strong contamination (0.12 ≤ PLI ≤ 0.58; 37 ≤ PLI ≤ 114, respectively, for rare earth elements and precious elements), while the degree of contamination indicated a moderate polymetallic contamination for rare earth elements and significant contamination for precious elements.

Heavy metal removal from sludge with organic chelators: Comparative study of N, N-bis(carboxymethyl) glutamic acid and citric acid.

The applicability and performance of a new generation of biodegradable chelator, N, N-Bis(carboxymethyl) glutamic acid (GLDA), for extracting heavy metals from sewage sludge was carried out and compared with citric acid (CA). Targeted metals included Cd, Co, Cu, Zn, Ni and Cr, and their contents in the raw sludge were 63.1, 73.4, 1103.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis), respectively. Metals were divided into six fractions including water soluble, exchangeable, carbonates bound, Fe-Mn bound, organic matters bound and residual fraction via chemical fractionation. Washing results showed that in general GLDA exhibited better performance compared with CA, with removal efficiency of 83.9, 87.3, 81.2, 85.6, 89.3 and 90.2% for Cd, Co, Cu, Zn, Ni and Cr, respectively at equilibrium pH = 3.3. Residual metals were better stabilized in the GLAD-washed sludge than in the CA-washed sludge, and were mostly tightly bonded to the residual fraction. Furthermore, CA promoted phosphorus (P) release while GLDA had an opposite effect and tended to retain P within sludge, which could be beneficial for further application in agricultural use. Findings from this study suggested that GLDA could be a potential replacement for refractory and less environmentally-friendly chelators in the extraction of metals from sludge.

New method of producing a more efficient coagulant for the treatment of water from seeds of moringa oleifera.

The coagulation is essential in raw water treatment. The most used coagulants are often of chemical origin and expensive and their use generates non-biodegradable residues. This is why innovative studies on the synthesis of natural coagulants based on plant extracts are very important. This study presents a new method of producing a coagulant for the treatment of water from seeds of moringa oleifera. The application of the new method is done in several steps: Harvesting moringa oleifera seeds, shelling, crushing the seeds, extracting oil from moringa oleifera powder, extracting salts from powder from moringa seeds oleifera, microfiltration with a 0.2 µm filter and lyophilization which gives the final product in dry form. We used the resulting product for coagulation of lake water with an initial turbidity of 40 NTU. This treatment reduced the turbidity of the water by almost 95 % when we used 0.7 mg of this coagulant per liter of water. Moringa has previously been used to produce coagulant but the peculiarity of this study is that it takes a very small amount of the synthesized product to effectively treat water. -The results of this research work have shown that the coagulant produced rom the seeds of Moringa oleifera can be used effectively for the treatment of surface water.-The residual turbidity obtained after the treatment of lake water with the coagulant produced was in accordance with the drinking water standard according to the World Health Organization (WHO) (less than 5 NTU).-The coagulant produced by this new method from moringa oleifera seed is an alternative to aluminum sulfate coagulant for water treatment.

Pathogenic Leptospira and water quality in African cities: A case study of Cotonou, Benin.

Leptospirosis is a waterborne zoonosis (60,000 infections and 1 million deaths annually). Knowledge about the disease in the urban context is surprisingly rare, especially in Africa. Here, we provide the first study of leptospires in waters within an African city. A simple centrifugation-based method was developed to screen waterborne leptospires from remote or poorly areas. Major ions, trace elements, stable isotopes and pathogenic Leptospira were then seasonally investigated in 193 water samples from three neighborhoods of Cotonou (Benin) with different socio-environmental and hydrographic characteristics. Firstly, no leptospire was detected in tap waters. Secondly, although surface contamination cannot be excluded, one groundwater well was found leptospire positive. Thirdly, pathogenic Leptospira mainly contaminated surface waters of temporary and permanent ponds (9.5% and 27.3% of total prevalence, respectively). Isotopic signatures suggest that leptospires occurred in pond waters formed at the beginning of the rainy season following low to moderate rainfall events. Nevertheless, Leptospira-containing waters possess physico-chemical characteristics that are similar to the spectrum of waters sampled throughout the three sites, thus suggesting that Cotonou waters are widely compatible with Leptospira survival. The frequent contact with water exposes Cotonou inhabitants to the risk of leptospirosis which deserves more attention from public health authorities.

Organochlorine pesticides contaminated soil decontamination using TritonX-100-enhanced advanced oxidation under electrokinetic remediation.

Remediation of organochlorine pesticides (OCPs)-contaminated soils is urgently required especially in China. Surfactants have emerged as reliable and efficient co-solvent for the treatment of hardly soluble organic pollutants in contaminated soil. Here, we report the use of TritonX-100 (TX-100) in advanced oxidation under electrokinetic technology (EK) for OCPs removal from a historically contaminated soil from a former pharmaceutical industrial wasteland. Result shows that TX-100 (10%) played a key role in soil remediation. In effect, after a treatment period of 15 days, pollutants washed ranged from 50.68% (4,4'-DDT) to 76.07% (HCB), when TX-100 was used as the electrolyte (EK-TX-100). A simple advanced oxidation of the soil using sodium persulfate (PS) under EK approach (EK-PS) was limited to achieve good removal efficiency of the pollutants; as the result of OCPs' hardly dissolvable nature. The achieved removal efficiency were comprised between 22.62% (2,4-DDT) and 55.78% (1,2,4,5-TCB). With the application of TX-100 as co-solvent (EK-TX-100/PS), the pollutants removal efficiency significantly improved (p < 0.05). The treatment efficiency was shifted and up to 88.05% (1,2,4-TCB) was achieved, while the lowest removal efficiency was 56.36% (4,4'-DDE). We come to the conclusion that the use of TX-100-enhanced advanced oxidation (EK-TX-100/PS) as a reliable treatment for remediating organochlorine contaminated soil.

Diagnosis and ecotoxicological risk assessment of 49 elements in sludge from wastewater treatment plants of Chongqing and Xiamen cities, China.

Limited information about the sludge quality is a major constraint for its usage and proper disposal. This study investigated the occurrence of 49 elements in sludge from 11 wastewater treatment plants (WWTPs) in Chongqing and Xiamen cities of China. The concentration of 46-detected elements ranged from 16.2 µg kg-1 (Pt) to 55.0 g kg-1 (Al) on dry solid basis in the sludge. The enrichment factor of most of the elements was > 1.5, indicating their possible anthropogenic origin. The precious metals had considerably higher enrichment factor ranging from 56.3 to 200,000. Principal component analysis clustered the samples from Chongqing and Xiamen separately to suggest strong spatial variations. Contamination factor, pollution loading index, and integrated pollution degree were calculated to evaluate the elemental pollution risk. The pollution loading index indicated unpolluted to highly polluted levels of the elements in the sludge. In addition, results from the ecotoxicological risk index showed an individual low to very high ecotoxicological risk posed by eight metal(loid)s (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in the WWTPs.

Assessment of the occurrence, spatiotemporal variations and geoaccumulation of fifty-two inorganic elements in sewage sludge: A sludge management revisit.

The limited information about the sludge quality has made its management a top environmental challenge. In the present study, occurrence and the spatiotemporal variations of 52 inorganic elements were investigated in the sludge samples from three wastewater treatment plants (WWTPs) in Xiamen city, China. The results showed, the occurrence of 49 elements with the concentrations in the range of >125-53500 mg kg-1 dry sludge (DS) for commonly used industrial metals, 1.22-14.0 mg kg-1 DS for precious metals, and 1.12-439.0 mg kg-1 DS for rare earth elements. The geo-accumulation studies indicated a moderate to high levels of buildup of some elements in the sewage sludge. Principal components analysis (PCA) indicated strong spatial and weak temporal variations in the concentrations of the elements. Therefore, the sludge disposal operations, based on the element concentrations, geoaccumulation and economic potential are suggested for each WWTP. Sludge from W1 and W2 were found suitable for agricultural usage, while that from W3 showed a higher economic potential for the recovery of precious metals. This study concludes that a comprehensive analysis of the elements in the sewage sludge could provide critical information for the disposal and management of the sludge.

Effect of nanoscale zero-valent iron and magnetite (Fe3O4) on the fate of metals during anaerobic digestion of sludge.

Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas renewable energy. In this study, two different iron nanoparticles [nanoscale zero-valent iron (nZVI) and magnetite (Fe3O4)] were used in the mesophilic AD processes (37 ± 1 °C) to improve biogas production. In addition, changes of heavy metal (Cd, Co, Cu, Zn, Ni and Cr) speciation during AD of sludge with and without iron nanoparticles have been investigated. Concentrations of metals in the initial sludge were as follows: 63.1, 73.4, 1102.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis) for Cd, Co, Cu, Zn, Ni and Cr, respectively. Sequential fractionation showed that metals were predominantly bonded to organic matter and carbonates in the initial sludge. Compared with AD without iron nanoparticles, the application of iron nanoparticles (at dose of 0.5% in this study) showed positive impact not only on biogas production, but also on improvement of metals stabilization in the digestate. Metals were found concentrated in Fe-Mn bound and residual fractions and little was accumulated in the liquid digestate and most mobile fractions of solid digestate (water soluble, exchangeable and carbonates bound). Therefore, iron nanoparticles when properly used, could improve not only biogas yield, but also regulate and control the mobilization of metals during AD process. However, our study also observed that iron nanoparticles could promote the immobilization of phosphorus within the sludge during AD, and more research is needed to fully address the mechanism behind this phenomenon and the impact on future phosphorus reuse.