Overview of biologically digested leachate treatment using adsorption

Biological process is effective in treating most biodegradable organic matter present in leachate; however, a significant amount of ammonia, metals and refractory organic compounds may still remain in this biologically digested leachate. This effluent cannot be released to receiving bodies until the discharge limit is met. Several physical/chemical processes have been practiced as post-treatment to remove the remaining pollutants including coagulation–flocculation, oxidation and adsorption. Adsorption is often applied in leachate treatment as it enhances removal of refractory organic compounds. This chapter will focus on works related to adsorption as one of the commonly used methods to treat biologically digested leachate further down to acceptable discharge limit

Overview of biologically digested leachate treatment using adsorption

Biological process is effective in treating most biodegradable organic matter present in leachate; however, a significant amount of ammonia, metals and refractory organic compounds may still remain in this biologically digested leachate. This effluent cannot be released to receiving bodies until the discharge limit is met. Several physical/chemical processes have been practiced as post-treatment to remove the remaining pollutants including coagulation–flocculation, oxidation and adsorption. Adsorption is often applied in leachate treatment as it enhances removal of refractory organic compounds. This chapter will focus on works related to adsorption as one of the commonly used methods to treat biologically digested leachate further down to acceptable discharge limit

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

Behavior of electro-osmotic dewatering of biological sludge with salinity

The salinity effect on electro-osmosis dewatering was investigated by measuring the solid content of sludge after dewatering. Three levels of salinity were studied, 5,000, 10,000, and 12,500 ppm. Coagulant chemicals such as alum, ferrous sulfate, and organic polyelectrolytes were used for some tests. Increasing the salinity from 5,000 to 10,000 ppm and 10,000 to 12,500 ppm was found to increase the sludge solid content about 88 and 28\%, respectively. A 2 V/cm increase in voltage intensity can also increase the solid content about 46\%. The effect of chemicals is evident at low salinity. At 5,000 and 10,000 ppm, addition of chemicals in average can enhance the sludge solid content about 44 and 16\%, respectively. Because of the electrolysis of salt solution and the release of chlorine gas, the pH of the sludge increased. Consequently the zeta potential of the sludge increased, which in turn results in an increase in dewatering rate. Therefore an S-shape solid content-time curve was observed for most of the operating conditions, contrary to the conventional shape of a linear increase followed with a decrease of rate before reaching zero rate

The binding chemistry and leaching mechanisms of zinc-bearing sludges in cementitious solidification/stabilization systems

This paper aims at studying the binding chemistry and leaching mechanisms of cement-based solidification of industrial Zn-bearing sludge. Two cement-based solidification systems were considered: one with cement alone and the other with cement and ny ash. Toxicity characteristic leaching procedure (TCLP), dynamic leaching test (DLT), and sequential chemical extraction (SCE) were employed in this study. TCLP and DLT results show that the sample with cement alone has lower leaching of zinc and calcium compared to the sample with cement and fly ash. SCE results show that zinc has the highest leaching in the oxide phase. Microstructures and crystalline phases of the solidified samples were examined by scanned electron microscopy (SEM) and x-ray diffraction (XRD), respectively. SEM images of solidified samples suggest that the presence of zinc might retard the hydration of cement and fly ash because identifiable hydration products of cement were no longer observed. For the solidified samples with the presence of zinc sludge, only calcium silicate (CS) was detected by XRD while calcium silicate hydrate (CSH) and calcium hydroxide crystal (CH) were not found. Moreover, zincite (ZnO) was found in those solidified samples by XRD. It is believed that zinc may have replaced calcium from calcium hydroxide to form zincite. The high leaching in the oxide phase from SCE, and the high leaching of calcium from TCLP also supported this finding. For the sludge sample solidified by OPC alone, the results from SEM and XRD indicate that zinc might react with calcium hydroxide and is likely to be trapped in the solidified cement matrix. This leads to low leaching of zinc from both TCLP and DLT. Although zincite was also observed in the sample with both OPC and PFA, the high leaching of zinc from this sample implies that OPC alone is more effective than a mixture of OPC and PFA in the solidification/stabilization process

Organically modified clays for pollutant uptake and environmental protection

Because of their natural abundance and widespread occurrence, clays have been used 'in the service of man' (Konta 1995) since antiquity, notably as the raw materials in pottery and ceramics. Similarly, the use of fuller's earth (a calcium-rich montmorillonite) as a scouring and cleaning agent of raw wool dates back to before 2000 BC (Robertson 1986). Clays have also long served as medicinal and therapeutic agents, among which Bolus Armenus (a red clay from Cappadocia) and terra sigillata (a kaolinite-rich material from the island of Lemnos) are well known for their efficacy in curing festering wounds, skin afflictions, and snake bites (Robertson 1986, Carretero et al. 2006, Droy-Lefaix and Tateo 2006). Likwise, Sudanese villagers along the Nile have traditionally used a local bentonite clay to rid river water of viruses and bacteria (Lund and Nissen 1986, Madsen and Schlundt 1989). For a description of the modern-day uses of clays and clay materials in various industries the reader is referred to the reviews by Murray (2003) and Harvey and Lagaly (2006). Clay therapy and many practical applications of clays rely on the ability of these minerals to sorb and retain harmful and undesirable substances from their immediate environment. The sorptive capacity of clays is related to their small particle size, extensive surface area, layer structure, and charge characteristics. The vast literature on the interactions of clay minerals, especially smectites, with small and polymeric organic molecules has periodically been reviewed (Mortland 1970, Theng 1974, 1979, Huang and Schnitzer 1986, Yariv and Cross 2002, Lagaly et al. 2006). Although the reactivity of these minerals might be expected to extend to anthropogenic and industrial pollutants, the use of smectites for environmental protection is a relatively recent development. Its emergence is prompted by a growing awareness that industrial pollutants pose a threat to environmental and human health, and the need to find inexpensive and environmentally friendly materials for pollution control (Kowalska et al. 1994, Xu et al. 1997, Prost and Yaron 2001). Here we assess the literature that has accumulated over the past two decades on the use of smectites and their organically modified forms as sorbents of non-ionic organic compounds and pollutants. As far as is possible, we will refer to key papers and reviews, rather than cite individual authors.B.K.G. Theng, G.J. Churchman, W.P. Gates & F. Yua