Development of a land use regression model for black carbon using mobile monitoring data and its application to pollution-avoiding routing

Black carbon is often used as an indicator for combustion-related air pollution. In urban environments, on-road black carbon concentrations have a large spatial variability, suggesting that the personal exposure of a cyclist to black carbon can heavily depend on the route that is chosen to reach a destination. In this paper, we describe the development of a cyclist routing procedure that minimizes personal exposure to black carbon. Firstly, a land use regression model for predicting black carbon concentrations in an urban environment is developed using mobile monitoring data, collected by cyclists. The optimal model is selected and validated using a spatially stratified cross-validation scheme. The resulting model is integrated in a dedicated routing procedure that minimizes personal exposure to black carbon during cycling. The best model obtains a coefficient of multiple correlation of R = 0.520. Simulations with the black carbon exposure minimizing routing procedure indicate that the inhaled amount of black carbon is reduced by 1.58% on average as compared to the shortest-path route, with extreme cases where a reduction of up to 13.35% is obtained. Moreover, we observed that the average exposure to black carbon and the exposure to local peak concentrations on a route are competing objectives, and propose a parametrized cost function for the routing problem that allows for a gradual transition from routes that minimize average exposure to routes that minimize peak exposure

Potential of sulfide-based denitrification for municipal wastewater treatment

Wastewater treatment through anaerobic carbon removal followed by sulfide-based denitrification for nitrogen removal offers significant advantages over conventional processes in terms of decreased sludge production and reduced energy requirements. While the process has been demonstrated to treat wastewater with very high sulfate concentrations resulting from saline water supply, this contribution assesses the potential of sulfide-based denitrification for a broader range of municipal wastewater characteristics. A mass balance-based calculation procedure was presented to determine the optimal recycle ratio and the corresponding effluent nitrogen concentrations in a pre-denitrification system. The calculation procedure was first validated with experimental data from literature and was then applied to various scenarios. The latter showed that legal effluent requirements may be achievable only for specific municipal wastewater streams with a low nitrogen concentration and an elevated sulfate content (>42 g S m(-3)), e.g. close to the sea, or if a significant amount of biodegradable carbon enters the anoxic reactor to stimulate auxiliary heterotrophic denitrification. A stoichiometric calculation illustrated that even with external carbon addition to supplement the sulfide-based denitrification, the total sludge production and aeration energy could still be reduced compared to a scenario with purely heterotrophic denitrification. Finally, it was shown that a broader range of wastewater types could be treated when applying nitrification-denitrification over nitrite instead of over nitrate, due to the lower sulfide and carbon requirements for the reduction of nitrite