Fiber failure frequency and causes of hollow fiber integrity loss

Ultrafiltration (UF) and microfiltration (MF) have been successfully applied in water treatment plants to remove particles, microorganisms and viruses. Up to 5 logs removal can be obtained; nevertheless, the water quality is influenced by compromised fibers. Several methods have been developed to monitor the integrity of a membrane system, but there is no clear picture of the occurrence and causes of fiber failure. In the present study, for different commercially available membranes, an annual fiber failure rate was found, mostly between I to 10 per million fibers. Data were gathered from the literature and acquired by contacting membrane manufacturers and water treatment plants. An overview of factors playing a role in fiber failure is given: strength of the membrane material (reviewed from the literature), operating conditions and incidents, such as failing pre-treatment, were identified to be important. It is believed that a certain level of membrane leakage is acceptable as long as the integrated multi-barrier treatment process has sufficient disinfection credits. From our data it was concluded that fiber failure rates of UF/MF membranes are acceptable, but a further reduction of this rate can reduce repair costs and installation down-time

Multi-scale Validation of an Agent-Based Housing Market Model

Validation is a vital step in any model that aspires to have an impact. In agent-based computational economics in particular, it is essential because, unlike most neoclassical economic models, the models are vastly complex and often unique in their kind [1, 2]. Importantly, they often require disaggregated data to specify attributes, behavioural rules and interactions among agents. Therefore, agent-based models require more time and effort to validate. There are numerous ways of validation in agent-based modelling discussed in the literature, e.g [1, 3–7]. Reviewing them is beyond the scope of this paper. Here we will focus on two dimensions of validation: empirical versus theoretical validation and micro- versus macroscale validation. In our agent-based model of the housing market, we have applied both ends of the two spectra