The objective of this research is to introduce a novel framework to quantify the risk of the reservoir system outside the design envelope, taking into account the risks related to flood-protection and hydro-energy generation under unfavourable reservoir element conditions (system element failures) and hazardous situations within the environment (flood event). To analyze water system behavior in adverse conditions, a system analysis approach is used, which is founded upon the system dynamics model with a causal loop. The capability of the system in performing the intended functionality can be quantified using the traditional static measures like reliability, resilience and vulnerability, or dynamic resilience. In this paper, a novel method for the assessment of a multi-parameter dynamic resilience is introduced. The multi-parameter dynamic resilience envelops the hydropower and flood-protection resilience, as two opposing demands in the reservoir operation regime. A case study of a Pirot reservoir, in the Republic of Serbia, is used. To estimate the multi -parameter dynamic resilience of the Pirot reservoir system, a hydrological model, and a system dynamic simulation model with an inner control loop, is developed. The inner control loop provides the relation between the hydropower generation and flood-protection. The hydrological model is calibrated and generated climate inputs are used to simulate the long-term flow sequences. The most severe flood event period is extracted to be used as the input for the system dynamics simulations. The system performance for five different scenarios with various multi failure events (e.g., generator failure, segment gate failure on the spillway, leakage from reservoir and water supply tunnel failure due to earthquake) are presented using the novel concept of the explicit modeling of the component failures through element functionality indicators. Based on the outputs from the system dynamics model, system performance is determined and, later, hydropower and flood protection resilience. Then, multi-parameter dynamic resilience of the Pirot reservoir system is estimated and compared with the traditional static measures (reliability). Discrepancy between the drop between multi-parameter resilience (from 0.851 to 0.935) and reliability (from 0.993 to 1) shows that static measure underestimates the risk to the water system. Thus, the results from this research show that multi-parameter dynamic resilience, as an indicator, can provide additional insight compared to the traditional static measures, leading to identification of the vulnerable elements of a complex reservoir system. Additionally, it is shown that the proposed explicit modeling of system components failure can be used to reflect the drop of the overall system functionality.

This paper discusses design principles and theoretical results for a new type of settling tank. Within the settling zone of the tank, sedimentation takes place in tube, as in a quiescent container of equal (3-5 cm) depth. The inlet, sludge and outlet zone are arranged for a continuous-flow rectangular (or circular) basin. A particle that enters the sludge zone is and stays removed, and the sludge can be removed by gravity or pumped from the sludge zone. Hydraulically, the process can be formulated in terms of horizontal-vertical-flow without short-circuiting. Tank loadings are 0.5 L/s per m2 to 1.5 L/s per m2 of tank surface area. The detention period of 15-20 minutes offers the same overall removal efficiency as 4-5 hours for classical one. Variations in flow are of little concern, provided that the maximum design flow is not exceeded. Scum is removed without difficulty from the tank as well as the sludge, and the sludge removal device will also act as a flocculator. This type of settling basin is suitable where sludge volumes are large or where putrefaction of sludge in contact with the flowing water is to be avoided.

The new approach of the study was to assess the consistency between the gas-particle partition coefficients of 16 EPA PAHs predicted by the ab/ad-sorption Dachs-Eisenreich model and the experimental results obtained within the field measurements. A total number of 29 air samples was obtained at 9 locations in Serbia. High Volume Air Sampler was applied, with quartz filters for collecting the atmospheric particles and polyurethane foam filters (PUF) for retaining the free gas molecules of PAHs. The results predicted by the model and experimental data were compared. Deviations between the measured and predicted f values were less than one order of magnitude for Flo, Phe, Ant, Flu, Pyr, B(a)A and Chr. For the PAHs with high molecular mass, B(b)F, B(k)F, B(a)P, I(1,2,3-cd)P, D(ah)A and B(ghi)P, very good agreement was confirmed, except for the data measured at the Oil refinery in Pancevo. Applied model underestimated the concentrations of PAHs in gas-phase for the low-molecular mass PAHs.