Environmental Engineering

The recovery of spent or waste lead acid batteries is important both for the management of lead input to the environment and to meet the lead demand of the market in a more energy and cost effective manner than primary production. As an important producer of lead acid batteries for the Middle Eastern and Eastern European market, Turkey seems to meet 22%–52% of its total lead demand by waste lead acid battery recovery. In this study, the wastes from Turkish waste lead acid battery recovery plants are identified and management strategies that are both technically sufficient and economically feasible for each of these wastes are complied. Furthermore, ranges of the amount of each waste generated per mass of final lead produced in these plants are estimated. Some of the most significantly generated wastes are lead containing dusts, wash water treatment sludges and slags from smelting furnaces with generation rates between 5–250, 1–150 and 5–100 kg t−1 of product lead, respectively. Many of these can be fed back to the recovery process inside the plants except a subset of slags that are called ‘final slag’ and have low (5%–6%) lead content. Final slags can either be recovered for the production of cement, road-filling materials or abrasives proven that they are in a non-leachable, stable state or should be stored at hazardous waste landfills. For improved environmental performance, newly emerging techniques that eliminate the generation of such slags are also discussed and suggested.

The objective of this study is to investigate the effect of phase-digestion (single-and two-phase) of molasses on energy production as methane in batch reactors. The effect of substrate to initial microorganism ratio (S/Xo as mg COD/mg VSS) on biogas production was also investigated for unfermented molasses. Experiments were performed in two sets of anaerobic batch reactors. The first set (Set 1) was operated with molasses which was not previously fermented. In order to investigate the effect of S/Xo ratio on methane yield and productivity, batch reactors were conducted at different S/Xo ratios of 0.5, 1, 1.5, 2, 2.5, 3 (mg sCOD/mg VSS). The results showed that the highest methane yield and productivity were achieved at an S/X0 ratio of 0.5 as 311 mL CH4/g sCODadded and 4 mol CH4/Lreactor.h, respectively. The second set (Set 2, i.e. the second-phase of a two-phase system) was conducted with the effluents of dark fermentation batch reactors operated with molasses. The reactors in Set 2 differed in their initial soluble COD (sCOD) concentrations, VFA compositions and VFA concentrations. S/Xo of reactors in Set 2 was also set as 0.5. The highest methane percent, methane yield and productivity obtained in Set 2 were 83%, 461 mL CH4/g sCODadded and 12 mol CH4/ Lreactor.h, respectively. INTRODUCTION Anaerobic digestion (AD) process has long been applied to the treatment of domestic and industrial wastes, wastewaters. Nowadays, however, this process has been considered to produce renewable bioenergy like hydrogen and methane by not only treating the wastes/wastewaters, but also using industrial and agricultural by-products. Especially, due to current imperative global issues such as petroleum depletion and global warming, worldwide attention has been paid to the AD process for bioenergy production. As a result a significant amount of literature study already exists about the improvement of energy efficiency of application and benefit of the AD process for hydrogen and/or methane production.

The efficient and economic management of waste activated sludge (WAS) requires a proper understanding of the sludge's material properties. Though there has been much study of WAS, an adequate linkage between its physical and chemical properties has been elusive. In particular, the conditioning and dewatering of WAS are expensive operations, and the addition of polymer to WAS leads to even more complex material behavior that is difficult to optimize. This paper reports on an extensive characterization of WAS, both with and without polymer conditioning. We combined the classical "jar test" approach with less conventional rheometric and electrokinetic measurements. In addition to the use of sampled WAS, a synthetic surrogate sludge was formulated, attempting to duplicate properties of WAS and allow more extensive characterization of a reproducible surrogate to WAS. Results with both the synthetic surrogate and WAS indicated that the traditional, electrokinetic, and rheolo...