Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This article reviews this phenomenon, focusing on copper ingestion and its health impacts, the physicochemical mechanisms and the microbial involvement on copper release, the techniques used to describe and understand this phenomenon, and the hydrodynamic effects. A conceptual model is proposed and the mathematical models are reviewed.

A fully quantitative cellular automaton (CA) biofilm model was developed. The model describes substrate and biomass as discrete particles existing and interacting in a specified physical domain. Substrate particles move by random walks, simulating molecular diffusion. Microbial particles grow attached to a surface or to other microbial particles, consume substrate particles, and duplicate if a sufficient amount of substrate is consumed. The dynamics of the system are simulated using stochastic processes that represent the occurrence of specific events, such as substrate diffusion, substrate utilization, biofilm growth, and biofilm decay and detachment. The ability of the CA model to predict substrate gradients and fluxes was evaluated by comparing model simulations to predictions from a traditional differential equations model. One and 2D CA models were evaluated. In general, CA model predictions of steady-state flux, biofilm thickness, and substrate gradients inside the biofilm fitted well the differenti...

Aims: This study used culture‐dependent and culture‐independent approaches to characterize bacterial communities in copper plumbing corrosion and to assess biofilm formation and copper resistance of heterotrophic bacteria isolated from copper pipes. Methods and Results: Water and copper pipes were collected from a cold‐water household distribution system affected by ‘blue water’ corrosion and presenting biofilm formation. Corrosion‐promoting ageing experiments were performed with conditioned unused copper pipes filled with unfiltered and filtered sampled water as nonsterile and sterile treatments, respectively. During 8 weeks, stagnant water within the pipes was replaced with aerated fresh water every 2 or 3 days. Total copper and pH were determined in sampled water, and copper pipe coupons were cut for microscopic analyses. Biofilms were extracted from field and laboratory pipes, and total DNA was isolated. Bacterial communities’ composition was analysed by terminal restriction fragment length polymorphism (T‐RFLP) and clonal libraries of 16S rRNA genes. Heterotrophic bacterial isolates were obtained from water and biofilm extracts and characterized in terms of biofilm formation capacity and copper minimum inhibitory concentration. The results indicated that copper concentration in stagnant water from nonsterile treatments was much higher than in sterile treatments and corrosion by‐products structure in coupon surfaces was different. Multivariate analysis of T‐RFLP profiles and clone sequencing showed significant dissimilarity between field and laboratory biofilm communities, and a low richness and the dominant presence of Gamma‐ and Betaproteobacteria in both cases. Several bacterial isolates formed biofilm and tolerated high copper concentrations. Conclusions: The study demonstrates microbially influenced corrosion (MIC) in copper plumbing. Gamma‐ and Betaproteobacteria dominated the corroded copper piping bacterial community, whose ability to form biofilms may be important for bacterial corrosion promotion and survival in MIC events. Significance and Impact of the Study: The characterization of micro‐organisms that influence copper plumbing corrosion has significant implications for distribution system management and copper corrosion control.

We used modeling to predict the energy and cost savings associated with the air-based, hybrid membrane-biofilm reactor (hybrid MfBR). This process is obtained by replacing fine-bubble diffusers in conventional activated sludge with air-supplying, hollow-fiber membrane modules. Evaluated processes included removal of chemical oxygen demand (COD), combined COD and total nitrogen (TN) removal, and hybrid growth (biofilm and suspended). Target concentrations of COD and TN were based on high-stringency water reuse scenarios. Results showed reductions in power requirements as high as 86%. The decrease mainly resulted from the dramatically lower air flows for the MBfR, resulting from its higher oxygen-transfer efficiencies. When the MBfR was used for COD and TN removal, savings up to US$200/1,000 m3 of treated water were predicted. Cost savings were highly sensitive to the costs of the membrane modules and electrical power. The costs were also very sensitive to membrane oxidation flux for ammonia, and the membrane life. These results suggest the hybrid MBfR may provide significant savings in energy and costs. Further research on the identified key parameters can help confirm these modeling predictions and facilitate scale-up.

A mathematical model to simulate the three-dimensional growth of multispecies anaerobic biofilms is developed and tested with a two-species biofilm composed of sulfate-reducing bacteria and methanogens. The numerical approach is based on the separation of biological, physical, and chemical phenomena so that quasi-steady-state conditions can be used in the solution. Simulations with Desulfovibrio vulgaris and Methanobacterium formicicum result in the formation of a biofilm heterogeneous in structure and composition. The model predicts different biofilm structures in the absence of sulfate, when a syntrophic association between the two organisms develops, and in the presence of sulfate, when the two organisms compete for the available hydrogen.