Wastewater disposal to landfill-sites: a synergistic solution for centralized management of olive mill wastewater and enhanced production of landfill gas

The present paper focuses on a largely unexplored field of landfill-site valorization in combination with the construction and operation of a centralized olive mill wastewater (OMW) treatment facility. The latter consists of a wastewater storage lagoon, a compact anaerobic digester operated all year round and a landfill-based final disposal system. Key elements for process design, such as wastewater pretreatment, application method and rate, and the potential effects on leachate quantity and quality, are discussed based on a comprehensive literature review. Furthermore, a case-study for eight (8) olive mill enterprises generating 8700 m(3) of wastewater per year, was conceptually designed in order to calculate the capital and operational costs of the facility (transportation, storage, treatment, final disposal). The proposed facility was found to be economically self-sufficient, as long as the transportation costs of the OMW were maintained at <= 4.0 (sic)/m(3). Despite that EU Landfill Directive prohibits wastewater disposal to landfills, controlled application, based on appropriately designed pre-treatment system and specific loading rates, may provide improved landfill stabilization and a sustainable (environmentally and economically) solution for effluents generated by numerous small- and medium-size olive mill enterprises dispersed in the Mediterranean region

Effects of pretreatment methods on solubilization of beet-pulp and bio-hydrogen production yield,” Int

a b s t r a c t Sugar processing wastewater and beet-pulp are two major waste streams of sugar-beet processing plants. Contrary to wastewater, beet-pulp is generally used as animal feed in cattle-raising industry. However, it can serve as a substrate for bio-hydrogen production which corresponds to a higher valorization of beet-pulp. Moreover, pretreatment of lignocellulosic materials like beet-pulp is needed in order to improve overall energy efficiency and enable economic feasibility of bio-hydrogen production. Therefore, the effect pretreatment methods (alkaline, thermal, microwave, thermal-alkaline and microwavealkaline) on bio-hydrogen production from sugar beet-pulp through dark fermentation were investigated in this study. Reactors pretreated with alkaline, microwave-alkaline and thermal-alkaline methods yielded significant solubilization of beet-pulp compared to others. Therefore, in the second phase of the study, they were used to pretreat the beetpulp which was then subjected to dark fermentation for bio-hydrogen production. Maximum bio-hydrogen production yield of 115.6 mL H 2 /g COD was observed in reactor which contained alkaline pretreated beet-pulp. ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. Introduction Hydrogen is a clean and environmentally friendly fuel since the combustion of hydrogen produces only water vapor instead of greenhouse gases like CO 2 . Furthermore, hydrogen has a high energy yield of 122 kJ/g, which is about 2.75 times greater than that of hydrocarbon fuels From the perspective of global environmental impacts, such as greenhouse effect and resource recovery, biological hydrogen production from renewable biomass reduces dependence on fossil fuel, decrease carbon dioxide emission and recovers bio-energy. Moreover, in order to establish Abbreviations: AD, Anaerobic Digestion; BES, 2-Bromoethanesulfonate; BM, Basal Medium; COD, Chemical Oxygen Demand; GC, Gas Chromatograph; HeAc, Acetic Acid; H-Bu, n-Butyric Acid; HePr, Propionic Acid; HRT, Hydraulic Retention A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 6 ( 2 0 1 1 ) 3 8 2 e3 8

Influent COD/TAN ratio affects the carbon and nitrogen removal efficiency and stability of aerobic granules

Two identical sequencing batch reactors (SBRs) seeded with aerobic granules were operated with varying chemical oxygen demand/total ammonia nitrogen (COD/TAN) ratios (1-30). R1 was operated at increasing COD/TAN ratios (7.5, 10, 20, 30), while R2 was operated at decreasing COD/TAN ratios (7.5, 5, 3.5, 2, 1). The results indicated that high COD/TAN ratios (7.5-30) provided high COD removal efficiency (around 92%) and low TAN removal (33%), favoring heterotrophs that form white, fluffy flocs and large granules. Maintenance of high treatment efficiency and granular stability is hard due to high growth rate of heterotrophs. On the other hand, low COD/TAN ratios (2-5) provided high TAN removal efficiency up to 100%, while COD removal was relatively low (60%); leading to small, dense, orange granules enriched in nitrifiers with slow-growing but stable characteristics. The optimum COD/TAN ratio in terms of high COD and TAN removal and granular stability was found as 7.5. It was found out that bacterial population distribution among nitrifiers and heterotrophs can be adjusted by changing influent COD/TAN ratios. This study also proposed the polysaccharide to protein (PS/PN) ratio in the extracellular polymeric substance of the granules as indicators of their stability and value of 0.6 as threshold level for stable granulation