Effect of dewatering and composting on helminth eggs removal from lagooning sludge under semi-arid climate

Occurrence, analysis of microplastics in sewage sludge and their fate during composting: A literature review

Microplastics (MP) are ubiquitous contaminants and their presence in sewage sludge has recently received attention as they may enter agro-ecosystems if sludge is used as organic soil amendment. Indeed, plastic particles (<5 mm) can be transported from wastewater and sewage sludge to the soil environment either directly within the plastic matrix or indirectly as adsorbed substances. In this paper, articles from 18 countries reporting the MP quantity and their characteristics in sewage sludge from wastewater treatment plants were reviewed and the MP concentration size and type were compared. The data show that MP abundance in sewage sludge ranged globally from 7.91 to 495 × 10³ particles kg^-1 with highest abundance of fiber shape and MP size of less than 500 μm. In this review, we summarized and discussed the methods most frequently used for extraction and characterization of MP in sewage sludge including organic matter removal, MP extraction; physical and morphological MP characterization and its chemical characterization for polymer identification. We also described the major factors potentially controlling the fate of MP during disposal strategies with particular focus on composting. We show that physical and microbiological factors are important for MP degradation during composting and suggest two remediation practices: (i) inoculation of the initial sludge with microbial plastic decomposers to remove MP from contaminated sewage sludge, and (ii) development of high temperature composting processes.

Diagnostic tools for the detection of taeniid eggs in different environmental matrices: A systematic review

The cestode family Taeniidae consists of the genera Echinococcus and Taenia, both of which include zoonotic tapeworms of serious public health importance. Various environmental matrices have been identified from which parasite transmission to animals and humans can occur, and many techniques for detecting taeniid eggs in different environments have been developed. However, the majority lack appropriate validation, and standardized egg isolation procedures are absent. This hampers interstudy comparisons and poses a challenge for future researchers when deciding which technique to implement for assessing taeniid egg contamination in a particular matrix. Therefore, the aim of this systematic review was to present an overview of the detection methods for taeniid eggs in the environment, to discuss and compare them, and to provide recommendations for future studies. In total, 1814 publications were retrieved from scientific databases, and, ultimately, data were systematically reviewed from 90 papers. The results provide an overview of numerous diagnostic tests for taeniid egg detection in (or on) water, food, soil, insects, objects, and air. These tools could be categorized as either conventional (light microscopy), molecular, or immunodetection tools. The relatively cheap microscopy techniques often lack sensitivity and are unable to identify a taeniid egg at the genus level. Nevertheless, several records ascribed a genus, or even species, to taeniid eggs that had been detected by light microscopy. Molecular and immunodetection tools offer better specificity, but still rely on the preceding egg recovery steps that also affect overall sensitivity. Finally, the majority of the methods lacked any attempt at performance evaluation and standardization, especially at the earlier stages of the analysis (e.g., sampling strategy, storage conditions, egg recovery), and viability was rarely addressed. As such, our review highlights the need for standardized, validated detection tools, that not only assess the extent of environmental contamination, but also the egg genus or species, and address viability.

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The cestode family Taeniidae contains species of serious public health importance.

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Parasite transmission may occur from several environmental matrices.

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Many methods for environmental detection of taeniid eggs have been developed.

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These often lack standardization, performance evaluation, and viability assessment.

Effectiveness of helminth egg reduction by solar drying and liming of sewage sludge

The present study is aimed at assessing the effectiveness of solar drying process in terms of helminth egg reduction in sewage sludge (SS) generated from an activated sludge wastewater treatment plant (WWTP) in Marrakesh city (Morocco). It is also engaged to highlight a synergic effect of liming (1% CaO) and solar drying on helminth egg reduction. The solar drying process was conducted for 45 days, in summer under a semi-arid climate in a pilot scale polycarbonate-based tunnel (2 m³). Before undergoing solar drying process, data showed an important load of helminth eggs including Ascaris sp., Schistosoma spp., Capillaria spp., Trichuris spp., Ankylostome spp., Toxocara spp., and Taenia spp. in limed sludge (LS) and non-limed sludge (NLS) (15.2 and 17.9 eggs/g, respectively). Ascaris eggs were the most abundant (11.2 and 13.5 eggs/g in LS and NLS, respectively). By the end of the solar drying process, a considerable removal of the total helminth eggs was recorded in LS and NLS (92.8% and 91.6%, respectively). A complete removal of Schistosoma spp., Capillaria spp., Trichuris spp., Toxocara spp. and Taenia spp. was noted in LS and NLS. In the case of Ankylostome spp., data showed a total removal in LS and 81% in NLS; however, the final load is in agreement with the standards (0.4 egg/g). As for Ascaris spp., neither liming nor solar drying process allowed a complete removal (91% and 90% in NLS and LS, respectively) and the final load (1.1 egg/g) does not fulfill the WHO requirements for an agricultural use. Principal component analysis (PCA) demonstrated a negative correlation between dry matter (DM) content (hence temperature) and helminth egg concentration. No significant synergic effect of liming and solar drying process was showed by statistical analysis. This is substantiating that temperature is the key parameter involved in helminth egg removal while undergoing solar drying of SS.

Fate of Ascaris at various pH, temperature and moisture levels

Soil-transmitted helminths (STH) are intestinal worms that infect 24% of the world's population. Stopping the spread of STH is difficult, as the eggs are resilient (can withstand high pH) and persistent (can remain viable in soils for several years). To ensure that new sanitation systems can inactivate STH, a better understanding of their resilience is required. This study assessed the inactivation of Ascaris eggs under various conditions, in terms of moisture content (MC) (<20 to >90%), temperature (20-50 °C) and pH (7-12.5). The results highlight that the exposure of Ascaris eggs to elevated pH (10.5-12.5) at temperatures ≤27.5 °C for >70 days had no effect on egg viability. Compounding effects of alkaline pH (≥10.5) or decreasing MC (<20%) was observed at 35 °C, with pH having more of an effect than decreasing MC. To accelerate the inactivation of STH, an increase in the treatment temperature is more effective than pH increase. Alkaline pH alone did not inactivate the eggs but can enhance the effect of ammonia, which is likely to be present in organic wastes.

Sludge nematodes, cestodes, and trematodes eggs variation from lagooning, activated sludge and infiltration-percolation wastewater treatment system under semi-arid climate

The prevalence and the identification of the helminth eggs load of raw sewage sludge was assessed of three different wastewater treatment systems. The results showed a variety of parasite species with following average concentrations; five taxa belonging to three classes nematodes, cestodes and trematodes were inventoried. The class of nematodes is the most diverse with 5 taxa. It is represented by the eggs of Ascaris sp., Capillaria sp., Trichuris sp., Toxocara sp., and Ankylostome sp., then comes the cestodes class, this is represented by the eggs of Tænia sp. The trematode class is represented by Schistosoma sp. The lagooning station of Chichaoua shows the highest load 7 species with Ascaris 21 eggs/g; Capillaria sp., 11 eggs/g; Trichuris sp., 6 eggs/g; Toxocara sp., 2 eggs/g and Ankylostome sp., 1 egg/g; Taenia sp., 2eggs/g; and Schistosoma sp., 1 egg/g. Infiltration-percolation sludge show the presence of 4 species of helminths eggs in sludge from anaerobic settling with different rates: 15 eggs/g for Ascaris sp., 15 eggs/g for Trichuris sp., 13 eggs/g for Capillaria sp., and 8 eggs/g for Taenia sp. However, in sand filter pool, the sludge helminth eggs load was decreased by 47% of Ascaris sp., 85% of Capillaria sp., and 75% of Taenia sp., Nevertheless, an increase of Trichuris eggs load was noted in the second sludge by 17%. Five helminth eggs was detected in primary sludge coming from decantation pools in activated sludge plant in Marrakech, that is Ascaris sp., with a load of 16 eggs/g; Capillaria sp., with 3 eggs/g, Trichuris eggs with 2 eggs/g; Taenia sp., with 4 eggs/g; and Schistosoma sp., with 2 eggs/g. The abatement load of Ascaris sp. with 81% and Schistosoma and Taenia sp., with 100% was noted in biological sludge. Nevertheless, an increase load of Capillaria and Trichuris eggs 81% and 75% respectively was observed in this sludge coming from biological pools. The distribution of parasitic helminth eggs is linked to the differences in demographic and socio-economic status, seasonal variation, physico-chemical characteristic of helminth eggs, and the purification wastewater system performance.