Presence of SARS-Coronavirus-2 RNA in Sewage and Correlation with Reported COVID-19 Prevalence in the Early Stage of the Epidemic in The Netherlands.

In the current COVID-19 pandemic, a significant proportion of cases shed SARS-Coronavirus-2 (SARS-CoV-2) with their faeces. To determine if SARS-CoV-2 RNA was present in sewage during the emergence of COVID-19 in The Netherlands, sewage samples of six cities and the airport were tested using four qRT-PCR assays, three targeting the nucleocapsid gene (N1-N3) and one the envelope gene (E). No SARS-CoV-2 RNA was detected on February 6, 3 weeks before the first Dutch case was reported. On March 4/5, one or more gene fragments were detected in sewage of three sites, in concentrations of 2.6-30 gene copies per mL. In Amersfoort, N3 was detected in sewage 6 days before the first cases were reported. As the prevalence of COVID-19 in these cities increased in March, the RNA signal detected by each qRT-PCR assay increased, for N1-N3 up to 790-2200 gene copies per mL. This increase correlated significantly with the increase in reported COVID-19 prevalence. The detection of the virus RNA in sewage, even when the COVID-19 prevalence is low, and the correlation between concentration in sewage and reported prevalence of COVID-19, indicate that sewage surveillance could be a sensitive tool to monitor the circulation of the virus in the population.

Removal and fate of Cryptosporidium parvum, Clostridium perfringens and small-sized centric diatoms (Stephanodiscus hantzschii) in slow sand filters.

The decimal elimination capacity (DEC) of slow sand filtration (SSF) for Cryptosporidium parvum was assessed to enable quantitative microbial risk analysis of a drinking water production plant. A mature pilot plant filter of 2.56m(2) was loaded with C. parvum oocysts and two other persistent organisms as potential surrogates; spores of Clostridium perfringens (SCP) and the small-sized (4-7microm) centric diatom (SSCD) Stephanodiscus hantzschii. Highly persistent micro-organisms that are retained in slow sand filters are expected to accumulate and eventually break through the filter bed. To investigate this phenomenon, a dosing period of 100 days was applied with an extended filtrate monitoring period of 150 days using large-volume sampling. Based on the breakthrough curves the DEC of the filter bed for oocysts was high and calculated to be 4.7log. During the extended filtrate monitoring period the spatial distribution of the retained organisms in the filter bed was determined. These data showed little risk of accumulation of oocysts in mature filters most likely due to predation by zooplankton. The DEC for the two surrogates, SCP and SSCD, was 3.6 and 1.8log, respectively. On basis of differences in transport behaviour, but mainly because of the high persistence compared to the persistence of oocysts, it was concluded that both spores of sulphite-reducing clostridia (incl. SCP) and SSCD are unsuited for use as surrogates for oocyst removal by slow sand filters. Further research is necessary to elucidate the role of predation in Cryptosporidium removal and the fate of consumed oocysts.

Sampling and quantifying invertebrates from drinking water distribution mains.

Water utilities in the Netherlands aim at controlling the multiplication of (micro-) organisms by distributing biologically stable water through biologically stable materials. Disinfectant residuals are absent or very low. To be able to assess invertebrate abundance, methods for sampling and quantifying these animals from distribution mains were optimised and evaluated. The presented method for collecting invertebrates consists of unidirectionally flushing a mains section with a flow rate of 1 ms(-1) and filtering the flushed water in two separate flows with 500 microm and 100 microm mesh plankton gauze filters. Removal efficiency from mains was evaluated in nine experiments by collecting the invertebrates removed from the mains section by intensive cleaning immediately subsequent to sampling. Of 12 taxa distinguished, all except case-building Chironomidae larvae (2%) and Oligochaeta (30%) were removed well (51-75%). Retention of invertebrates in 100 microm filters was evaluated by filtering 39 filtrates using 30 microm filters. Except for flexible and small invertebrates such as Turbellaria (13%), Nematoda (11%) and Copepoda larvae (24%), most taxa were well retained in the 100 microm filters (53-100%). During sample processing, the method for taking sub-samples with a 10 ml pipette from the suspension of samples with high sediment concentrations was found to perform well in 75% of the samples. During a 2-year national survey in the Netherlands and consecutive investigations, the method appeared to be very suitable to assess the abundance of most invertebrate taxa in drinking water distribution systems and to be practicable for relatively inexperienced sampling and lab technicians. Although the numbers of small, less abundant or sessile taxa were not accurately assessed using the method, these taxa probably should not be the primary focus of monitoring by water utilities, as consumer complaints are not likely to be caused by these invertebrates. The accuracy of quantifying small invertebrates was further improved, however, by filtering the 100microm filtrate with a 30microm mesh plankton gauze filter.

Accumulation and elimination of lanthanum by duckweed (Lemna minor L.) as influenced by organism growth and lanthanum sorption to glass.

Lanthanide emissions to the environment increase as a result of the growing industrial applications of these elements. However, robust data to evaluate the environmental fate of lanthanides are scarce. This article describes the accumulation and elimination of lanthanum (La) by common duckweed (Lemna minor L.). Speciation modeling was performed to assure that solubility products were not exceeded. It also showed that La was predominantly associated with ethylenediaminetetraacetic acid (EDTA). Lanthanum concentrations in plants and medium and the amounts sorbed to glass vessels were quantified by using the radioisotope 140La. The amount of La adsorbed on the glass reached values of 25% of the total La present. A model was formulated to describe La uptake in exponentially growing duckweed in the presence of an adsorptive surface. Growth-induced dilution appeared more efficient in lowering plant La concentrations than actual elimination. An elimination study revealed two compartments, of which the smallest eliminated 50 times faster than the bigger compartment, which eliminated mainly by growth dilution. The average bioconcentration factor was 2,000 L/kg fresh weight and 30,000 L/kg dry weight, comparable with those of other higher plants. At the applied concentration of 10 nM, no effects were observed on duckweed growth. However, the high bioconcentration factor warrants monitoring of lanthanide emissions.