Comprehensive comparison of water quality risk and microbial ecology between new and old cast iron pipe distribution systems.

The effects of cast iron pipe corrosion on water quality risk and microbial ecology in drinking water distribution systems (DWDSs) were investigated. It was found that trihalomethane (THMs) concentration and antibiotic resistance genes (ARGs) increased sharply in the old DWDSs. Under the same residual chlorine concentration conditions, the adenosine triphosphate concentration in the effluent of old DWDSs (Eff-old) was significantly higher than that in the effluent of new DWDSs. Moreover, stronger bioflocculation ability and weaker hydrophobicity coexisted in the extracellular polymeric substances of Eff-old, meanwhile, iron particles could be well inserted into the structure of the biofilms to enhance the mechanical strength and stability of the biofilms, hence enhancing the formation of THMs. Old DWDSs significantly influenced the microbial community of bulk water and triggered stronger microbial antioxidant systems response, resulting in higher ARGs abundance. Corroded cast iron pipes induced a unique interaction system of biofilms, chlorine, and corrosion products. Therefore, as the age of cast iron pipes increases, the fluctuation of water quality and microbial ecology should be paid more attention to maintain the safety of tap water.

Annular-shaped stenosis in the ureter: Caution should be taken.

OBJECTIVE: To draw the attention of clinicians and avoid the misdiagnosis, we investigate the relationship between annular-shaped stenosis under ureteroscopy and the clinicopathological features and prognosis in patients with primary urothelial carcinoma of the ureter that have been treated by radical nephroureterectomy. METHOD: We reviewed the records of patients with primary urothelial carcinoma of the ureter who had received radical nephroureterectomy in our hospital between January 2014 and June 2020. Based on the luminal morphology of the ureteral lesion, patients were divided into two groups: Group A for annular stenosis and Group B for non-annular stenosis. The logistic regression and Cox proportional-hazards models were used to explore the relationship between annular stenosis and clinicopathological findings. RESULTS: We investigated a total of 147 patients in this study, including 30 patients (20.4%) in Group A and 117 (79.6%) patients in Group B. The proportion of patients with diabetes mellitus was significantly higher in group A than in group B (66.6% vs. 38.5%, P = 0.006), and the percentage of patients undergoing ureteroscopy with biopsy was also significantly higher in group A than in group B (100% vs. 35.9%, P < 0.001). Besides, the logistic regression model revealed that annular-shaped stenosis was correlated to advanced T-stage (P = 0.002) and worse tumour grade (P < 0.001). During a median follow-up of 35 months (range: 6-73), 45 (30.6%) patients died, including 35 (23.8%) who died of ureteral carcinoma. The 5-year overall survival rate in Group A was significantly lower than in Group B (33.7% vs. 56.1%, P = 0.004). Similarly, the 5-year cancer-specific survival rate in Group A was also considerably lower than Group B (36.7% vs. 64.8%, P = 0.009). According to the multivariate Cox regression analysis that included only preoperative parameters, annular-shaped stenosis was an independent risk factor for both overall survival and cancer-specific survival (P = 0.006, P = 0.012, respectively). CONCLUSION: Annular-shaped stenosis indicates high carcinoma invasiveness and poor prognosis for patients with primary transitional cell carcinoma of the ureter. This condition can be easily misidentified, so clinicians should pay more attention when making diagnoses. Additionally, we discovered that diabetes mellitus may contribute to the development of annular stenosis.

Effects of cast iron pipe corrosion on nitrogenous disinfection by-products formation in drinking water distribution systems via interaction among iron particles, biofilms, and chlorine.

The effects of cast iron pipe corrosion on nitrogenous disinfection by-products formation (N-DBPs) in drinking water distribution systems (DWDSs) were investigated. The results verified that in the effluent of corroded DWDSs simulated by annular reactors with corroded cast iron coupons, typical N-DBPs, including haloacetamides, halonitromethanes, and haloacetonitriles, increased significantly compared with the influent of DWDSs. In addition, more dissolved organic carbon, adenosine triphosphate, and iron particles were simultaneously detected in the bulk water of corroded DWDSs, thereby indicating that abundant iron particles acted as a "protective umbrella" for microorganisms. Under the condition of corroded DWDSs, the extracellular polymeric substances gradually exhibited distinct characteristics, including a higher content and lower flocculation efficiency, thereby resulting in a large supply of N-DBPs precursors. Corroded cast iron pipes, equivalent to a unique microbial interface, induced completely distinct microbial community structures and metabolic functions in DWDSs, thereby enhancing the formation of N-DBPs. This is the first study to successfully reveal the interactions among iron particles, biofilms, and chlorine in DWDSs, which may help to fully understand the biofilm transformation and microbial community succession in DWDSs.