Detection of SARS-CoV-2 RNA in Bivalve Mollusks by Droplet Digital RT-PCR (dd RT-PCR)

Bivalve shellfish are readily contaminated by human pathogens present in waters impacted by municipal sewage, and the detection of SARS-CoV-2 in feces of infected patients and in wastewater has drawn attention to the possible presence of the virus in bivalves. The aim of this study was to collect data on SARS-CoV-2 prevalence in bivalve mollusks from harvesting areas of Campania region. A total of 179 samples were collected between September 2019 and April 2021 and were tested using droplet digital RT-PCR (dd RT-PCR) and real-time RT-PCR. Combining results obtained with different assays, SARS-CoV-2 presence was detected in 27/179 (15.1%) of samples. A median viral concentration of 1.1 × 102 and 1.4 × 102 g.c./g was obtained using either Orf1b nsp14 or RdRp/gene E, respectively. Positive results were unevenly distributed among harvesting areas and over time, positive samples being more frequent after January 2021. Partial sequencing of the spike region was achieved for five samples, one of which displaying mutations characteristic of the Alpha variant (lineage B.1.1.7). This study confirms that bivalve mollusks may bioaccumulate SARS-CoV-2 to detectable levels and that they may represent a valuable approach to track SARS-CoV-2 in water bodies and to monitor outbreak trends and viral diversity.

Recovery and utilization of phosphorus from fruit and vegetable wastewater

Excessive discharge of phosphorus into the water bodies is the key factor to cause eutrophication. The fruit and vegetable wastewater contains large amounts of phosphorus, and it may be directly discharged into water bodies, which has a great burden on the municipal sewage pipe network. Therefore, coagulation was used to remove phosphorus, recovered the phosphorus from the wastewater into the precipitate, and then the precipitate was pyrolyzed as an efficient adsorbent for phosphate removal. By comparing the adsorption effects of adsorbents (XT-300, XT-400, and XT-500) with pyrolysis temperatures of 300 °C, 400 °C, and 500 °C on phosphate in actual phosphorus-containing wastewater and simulated phosphorus-containing wastewater at different adsorbent dosage (4 g/L, 7 g/L, and 10 g/L), it was found that XT-300 had the best performance of adsorption, and the adsorption of phosphate was endothermic and obeyed the Langmuir isotherms and Elovich kinetics. The influence of pH, coexisting anions, and the structure of XT-300 revealed that the removal of phosphate was associated with electrostatic attraction, pore filling, but could not be determined whether it was related to surface precipitation. This study provides a way and method for the recovery and utilization of phosphorus in fruit and vegetable wastewater and proves that the synthetic adsorbent was an efficient phosphorus adsorbent. In the long term, we can try to use the adsorbent after phosphorus adsorption to promote plant growth in agricultural systems.

Municipal sewage sludge as a source of microelements in sustainable plant production: a laboratory lysimeter study

The aim of the work was to characterize the samples of sewage sludge (SSL) originated from the Wastewater Treatment Plant Piešťany (TAVOS, a.s., Trnava, Slovakia) in terms of their potential application into the soils. Within the physico-chemical characterization of SSL, the samples were analysed in terms of the values of pH, cation exchange capacity (CEC), total organic carbon (TOC), water holding capacity (WHC), as well as the presence of heavy metals. It was found that SSL contained significant amounts of microelements Zn (1,269 mg.kg-1, d.w.) and Cu (224 mg.kg-1, d.w.). Laboratory lysimeter experiments involving the application of SSL into the top layer of agriculturally used soil (0 – 10 cm) forming a soil column, in which seedlings of tobacco (Nicotiana tabacum L.) were cultivated, showed that in the case of SSL application in the highest permitted amounts (15 t.ha-1) only 0.11 % Zn and 0.07 % Cu were released into the soil eluate during a 28 day of exposure, while in tobacco plants 0.13 % Zn and 0.05 % Cu were accumulated from the total amount of Zn and Cu originated from the application of SSL (Zn – 133 mg and Cu – 23.5 mg). When applying SSL in amount 30 t.ha-1 i.e., in the dose exceeding the permitted limits, only 0.02 % Zn and 0.04 % Cu were released into the soil eluate and 0.16 % Zn and 0.09 % Cu were accumulated in tobacco plants from the applied amount of SSL (Zn – 267 mg and Cu – 47.0 mg).

Sanitary sewage

The treatment and disposal of domestic sewage is one of Brazil's main challenges. Sewage composition varies with the habits of the population and the frequency with which new contaminants are released into the environment. This study is a bibliographical review of the main aspects related to the characterization and composition of sanitary sewage, types of sewage treatment systems and pertinent legislation; and toxicity of domestic effluents. The review was based on publications available on Science Direct, Google Scholar and Scielo, as well as on printed publications, relevant legislation, and normative instructions. The research period adopted for the selection of publications was from 2005 to 2021. We found out that, in addition to the levels of organic matter from domestic sewage, residues from products used in daily life, such as pharmaceuticals and cleaning products, can be found in effluents in concentrations harmful to the environment. Often, the types of treatment used in municipal sewage treatment plants do not efficiently remove these contaminants. Thus, even if sewage is treated to meet the limits required for the physical-chemical and biological parameters established by law, domestic effluent can present a high potential for toxicity to various aquatic species such as microcrustaceans, mollusks and fish. Thus, ecotoxicological analyses represent a remarkable mechanism for indicating the efficiency of removal of emerging contaminants present in treated sanitary effluent, in addition to indicating the deleterious effects caused by these residues to the environment and ecosystems associated with the receiving water body.

Improving the photobioreactor operation efficiency in the technological scheme of wastewater treatment

Conventional process schemes of municipal sewage water treatment, advantages, and disadvantages of the methods applied when removing biogenic elements were considered. It was shown that the existing shortcomings cause additional explicit costs and difficulties when disposing of the resulting waste. Low efficiency of the removal processes themselves causing residual concentrations of biogenic elements in the treated sewage water was also shown. A process scheme for treating municipal sewage water was proposed. It includes the use of a photobioreactor of a proposed design for the removal of biogenic elements due to the metabolism of microalgae. It was experimentally shown that the use of Euglena gracilis strain for removal of phosphates in initial concentrations of 4, 7, and 14 mg/dm3 from sewage water is the most efficient way. It makes it possible to reduce these concentrations to residual 0…0.55 mg/dm3 in four days. A 3.75…5.58 times increment of microalgae biomass during this period was also shown. A mathematical model was constructed for calculating the time of staying the sewage water and microalgae mixture in a photobioreactor to achieve the required degree of removal of biogenic elements. Based on the proposed model and experimental studies, the required time of staying in the rector working area was calculated. It was shown that with the use of Euglena gracilis strain but without removal of biogenic elements at previous purification stages (process schemes including only mechanical purification), the time of mixture staying in the working zone was 37.81 hrs. With partial removal of biogenic elements at the stage of biological treatment (0.55 mg/dm3 total nitrogen, 0.91 mg/dm3 ammonium nitrogen, 0.44 mg/dm3 phosphates), this time was reduced to 26.66 hrs. It was found that the use of Euglena gracilis strain instead of Chlorella vulgaris (FC-16) in the removal of phosphates results in a 2-time increase in the process efficiency and a 50 % decrease in time of mixture staying in the working zone. Recommendations for calculating geometric parameters of photobioreactors of the proposed design were given for use in the process schemes

Biogas Production through Co-Digestion of Olive Mill with Municipal Sewage Sludge and Cow Manure

The treatment of olive mill (OM) residues from agricultural facilities is a daunting challenge since tremendous amounts are disposed per annum that should be treated. One of the promising treatment methods is the anaerobic methanogenic digestion of OM residues. In current investigations, the anaerobic digestion of the OM substrate is enhanced through mixing its slurries with sewage sludge (SS) or with cow manure (C), which consists of the kernels for the digestion process. Besides feedstock, other operational parameters such as hydraulic retention time (HRT), temperature and pH have a great impact on the biogas production rate and quality. Experimental investigations were conducted by means of the anaerobic biodegradation of the substrate for OM-SS and -C using a batch reactor under mesophilic conditions and foreseen HRT for 30 days. Almost neutral pH values of 7.4-7.6 were found for the anaerobic treatment of the substrate for OM-SS, and a slightly acidic pH in the range of 4.8-5.3 was found for the anaerobic treatment of the substrate for OM-C. The results revealed that the biogas production for OM-SS and -C exceeded 0.07 and 0.31 LBiogas/(LFerm·day), respectively. Regarding the COD reduction, its removal efficiency was obtained as 46.1 and 53.8% for OM-SS and -C respectively. For economic concerns, significant methane yields were attained as 56.8 and 115.8 [LCH4/kgCOD] for the OM-SS and -C substrates, respectively. In virtue of these remarkable merits, anaerobic methanogenic digestion should be adapted to a commercial scale for the treatment and biogas production of OM residues.