Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system

While pipe biofilms in DWDSs (drinking water distribution systems) are thought to affect the quality of distributed water, studies regarding the microbial processes are impeded by the difficulties in accessing biofilm undisturbed by DWDS maintenance. In this study, pipe sections were removed from a fully operational DWDS for biofilm sampling over two years and three months, and before and after start of ultrafiltration (UF) with coagulation treatment in the drinking water treatment plant (DWTP). Water (n = 31), surface biofilm (obtained by swabbing, n = 34) and deep pipe biofilm (obtained by scraping, n = 34) were analyzed with 16S rRNA gene amplicon sequencing; with flow cytometry, and chemical and natural organic matter (NOM) analysis as additional parameters for water quality. UF with coagulation decreased the total cell concentration in the DWDS bulk water from 6.0 × 105 ± 2.3 × 105 cells per ml to 6.0 × 103 ± 8.3 × 103 cells per ml, including fluctuations due to seasonal change, as well as decreasing most analyzed fractions of NOM. UF treatment of the water revealed that 75% ± 18% of the cells in the water originated from DWDS biofilm, confirmed by SourceTracker analysis, with the rest of the cells likely released from biofilm on DWTP storage tanks. Following UF start, the ASVs (amplicon sequence variants) in the deep pipe biofilm decreased, and Evenness and Shannon diversity indices decreased, reflecting the community's response to the new environment created by the altered water quality. The pipe biofilm community was dominated by ASVs classified as Nitrosomonadaceae, Nitrospira, Hyphomicrobium and Sphingomonas, with relative abundances ranging from 5–78%, and also included ASVs of genus Mycobacterium, genus Legionella and order Legionellales. This community composition, together with the observation that turnover of nitrogen compounds was unchanged by UF start, indicate that nitrification in the DWDS was localized to the pipe biofilm

Long-term follow-up of functioning after spinal surgery in patients with Rett syndrome

In a prospective study, 23 consecutive girls with Rett syndrome and neuromuscular scoliosis were evaluated for functioning at a long-term follow-up. The patients had mostly improved, which was confirmed by their parents. Rett syndrome is associated with neuromuscular scoliosis and has a typically long C-shaped thoracolumbar kyphoscoliosis. Prospective long-term follow-up studies related to these patients total situation are sparse. Most studies focus on the Cobb angle of the scoliosis, whereas parents are mainly concerned about the girls continued functioning. Twenty-three patients with Rett syndrome and neuromuscular scoliosis were evaluated preoperatively from 1993 to 2002. At follow-up, 19 patients remained in the study. Three patients died (not due to surgery), and one patient could not participate because it was too far to travel. Mean follow-up time was 74 months (range 49-99 months). The assessments comprised the sitting balance, seating supports in wheelchair, weight distribution, time used for rest, care given, and angle of scoliosis. Follow-up questionnaires and two-open-ended questions about the positive and negative effects of surgery were sent to parents. Sitting balance, number of seating supports in wheelchair, weight distribution, time used for rest, and the Cobb angle had all improved after surgery. The parents assessed improvement in seating position, daily activities, time used for rest, and cosmetic appearance. We can conclude that the stabilized spine resulted in sufficient strength to keep the body upright with the possibility of looking around at the surroundings more easily. The girls got better seating position with less need for seating adaptations in the wheelchair and with reduced time needed for resting during the day. Finally we can conclude that the indication for surgery is to get a better posture which lead to less risk of pressure sores, and that un upright position lead to better possibility to easily breath with fewer episodes of pneumonia and a better general health as result. The evidence of positive surgical effects for girls with Rett syndrome is of great importance in indication for surgery in the decision-making process.The original publication is available at www.springerlink.com: Eva-Lena Larsson, Stig Aaro, Peter Ahlinder, Helena Normelli, Hans Tropp and Birgitta Öberg, Long-term follow-up of functioning after spinal surgery in patients with Rett syndrome, 2009, EUROPEAN SPINE JOURNAL, (18), 4, 506-511. http://dx.doi.org/10.1007/s00586-008-0876-6 Copyright: Springer Science Business Media http://www.springerlink.com/</p

Impact of UV irradiation at full scale on bacterial communities in drinking water

Water in a full-scale drinking water treatment plant was irradiated with ultraviolet (UV) doses of 250, 400, and 600 J/m2, and the effect on bacterial communities investigated using 16s rRNA gene amplicon sequencing, heterotrophic plate counts (HPCs), coliform, and Escherichia coli counts. The bacteria in the irradiated water were also analyzed following storage for 6 days at 7 °C, to approximate the conditions in the distribution system. The log10 reduction of HPCs at 400 J/m2 was 0.43 ± 0.12. Phylogenetic examination, including DESeq2 analysis, showed that Actinobacteria was more resistant to UV irradiation, whereas Bacteroidetes was sensitive to UV. Phylum Proteobacteria contained monophyletic groups that were either sensitive or resistant to UV exposure. The amplicon sequence variants (ASVs) resistant to UV irradiation had a greater average GC content than the ASVs sensitive to UV, at 55% ± 1.7 (n = 19) and 49% ± 2.5 (n = 16), respectively. Families Chitinophagaceae, Pelagibacteraceae, Holophagaceae, Methylophilaceae, and Cytophagaceae decreased linearly in relative abundance, with increasing UV dose (P < 0.05, Pearson’s correlation). When irradiated water was stored, Chitinophagaceae, Comamonadaceae, and Flavobacteriaceae families decreased in relative abundance, whereas ACK-M1, Mycobacteriaceae, and Nitrosomonadaceae were increasing in relative abundance. This suggests that the impact of UV irradiation cannot only be considered directly after application but that this treatment step likely continues to influence microbial dynamics throughout the distribution system

Succession of bacterial biofilm communities following removal of chloramine from a full-scale drinking water distribution system

Abstract Monochloramine is used to regulate microbial regrowth in drinking water distribution systems (DWDS) but produces carcinogenic disinfection byproducts and constitutes a source of energy for nitrifying bacteria. This study followed biofilm-dispersed microbial communities of a full-scale DWDS distributing ultrafiltered water over three years, before and after removal of monochloramine. Communities were described using flow cytometry and amplicon sequencing, including full-length 16S rRNA gene sequencing. Removal of monochloramine increased total cell counts by up to 440%. Increased abundance of heterotrophic bacteria was followed by emergence of the predatory bacteria Bdellovibrio, and a community potentially metabolizing small organic compounds replaced the nitrifying core community. No increased abundance of Mycobacterium or Legionella was observed. Co-occurrence analysis identified a network of Nitrosomonas, Nitrospira, Sphingomonas and Hyphomicrobium, suggesting that monochloramine supported this biofilm community. While some species expanded into the changed niche, no immediate biological risk to consumers was indicated within the DWDS