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Colloidal carbon interference in the treatability of pulp and paper wastewater by MBR

- Scholes, Emily, Brook-Carter, Phillip, Verheyen, Vincent

  • Authors: Scholes, Emily , Brook-Carter, Phillip , Verheyen, Vincent
  • Date: 2019
  • Type: Text , Journal article
  • Relation: Journal of Environmental Chemical Engineering Vol. 7, no. 5 (2019), p. 1-9
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  • Description: Pulp and paper wastewaters are challenging to treat due to their variability, complexity and toxicity. Membrane Bioreactor’s (MBR’s) provide high-quality filtrates but are subject to periods of low filterability / high capillary suction time (CST) which potentially limit their use in this application. There is a paucity of published literature concerning long-term operational issues in full-scale, industrial MBR’s. We hypothesised that either changes of bacterial population, alteration/reduction of bacterial metabolism or bacterial production of extra-cellular polymers (ESPs) increased CST and reduced filterability. This study, conducted over two years at the 16.4MLD Gippsland Water Factory, was structured to inform this bacterial centric hypothesis. However, no shifts in bacterial population were seen as causative of high CST and microbial stress levels and biological activity were observed to be low during high CST and no sign of toxicity was found. The strongest correlator with CST was the concentration of colloidal Total Organic Carbon of the mixed liquor suspended solids (MLSS) supernatant (following centrifugation). The carbonaceous colloids accumulated in the supernatant were named ‘Non-Centrifugable Total Organic Carbon’ (NCTOC). Their accumulation in the MLSS was found be due to their biologically refractory nature and their retention by the MBR membrane. The accumulation of NCTOC typically followed a period where the influent had a high colour and a high sodium to calcium ratio, which is consistent with a pulping by-product called ‘Black Liquor’. Additional experiments with Black Liquor allowed us to conclude that high CST can be produced by addition of Black Liquor.

Differential evolution algorithm for predicting blast induced ground vibrations

- Saadat, Mahdi, Hasanzade, Ali, Khandelwal, Manoj

  • Authors: Saadat, Mahdi , Hasanzade, Ali , Khandelwal, Manoj
  • Date: 2015
  • Type: Text , Journal article
  • Relation: International Journal of Rock Mechanics and Mining Sciences Vol. 77, no. (2015), p. 97-104
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  • Description: 1. Introduction One of the most crucial problems in construction blasting is to predict and then mitigate the ground vibration [1]. Blast-induced ground vibration is considered as one of the most important environmental hazards of mining operations and civil engineering projects. Intense vibration can cause critical damage to structures and plants nearby the open-pit mines, dams, and mine slopes, etc [2] and [3]. Researchers who deals with this undesirable phenomenon take into account various range of parameters in order to mitigate the detrimental effects of blasting. Blast influencing parameters can be divided into two categories [2]: (a) Uncontrollable parameters, such as geological and geotechnical characteristics of the rockmass. (b) Controllable parameters, such as burden, spacing, stemming, sub-drilling, delay time, etc.

On robustness analysis of linear vibrational control systems

- Cheng, Xiaoxiao, Tan, Ying, Mareels, Iven

  • Authors: Cheng, Xiaoxiao , Tan, Ying , Mareels, Iven
  • Date: 2018
  • Type: Text , Journal article
  • Relation: Automatica Vol. 87, no. (2018), p. 202-209
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  • Description: By injecting high frequency dither signals, it is possible to stabilize an inverted pendulum without any feedback. The concept of the vibrational control system is thus proposed to provide extra design freedom in stabilization or other performance indexes. Although various vibrational control algorithms have been proposed and implemented in literature, little work has been done to show their robustness with respect to disturbances and uncertainties. This paper focuses on the robustness analysis of linear vibrational control systems with additive disturbances. By applying perturbation techniques, the linear vibrational control system is shown to be input-to-state stable with respect to disturbances. When disturbances are periodic, frequency analysis technique obtains a less conservative estimate of the ultimate bound of the system, indicating that disturbances with high frequencies lead to relatively small ultimate bounds. When additive state-dependent disturbances are considered, weak averaging techniques can be used to show the robustness of the system when bounded disturbances are slow time-varying. Numerical results support the theoretic analysis.
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