Human Cell Culture, a Pertinent In Vitro Model to Evaluate the Toxicity of Landfill Leachate/Sewage Sludge. A Review

Abstract

Both landfill leachate and sewage sludge are complex mixtures of many potentially toxic substances in unknown and unpredictable amounts and concentrations. Both types of matrices can pose a risk to human health and the functioning of ecosystems if released into the environment. Therefore, constant monitoring of the toxicity of these mixtures is necessary. However, traditional methods of analysis of sewage sludge/landfill leachate are mainly based on physicochemical studies that do not fully reflect the effects of these mixtures on living organisms. For this purpose, research based on biological models, including mammalian, mainly human, cells is recommended and increasingly implemented. A variety of cytotoxicity tests, based on various metabolic transformations in living cells, are a very useful tool in landfill leachate/sewage sludge toxicology studies. This paper reviews the methods used in the study of the cytotoxicity of environmental matrices and the cell lines used in these studies as biological models.

Advances in sewage sludge application and treatment: Process integration of plasma pyrolysis and anaerobic digestion with the resource recovery

“…Owing that SS contains toxic HMs, pathogens and other organic micro pollutants, hence environmental contamination. Landfill leachate and SS both contains complex toxic substances with random and unknown concentration, when discharged into the environment, it can harm living creatures and affect working process of ecosystem [ 87 ]. Apart from this, when sludge is landfilled, it generates some greenhouse gases during decomposition of organic material.…”

“… Treatment Parameter Principles Drawbacks Benefits Reference Landfilling – A bottom liner, a leachate collection system, a cover, and the natural hydrogeologic setting. Generation of leachate, waste of valuable organic/inorganic materials, emission of greenhouse gases if not engineered Cheap process with no energy consumption, reduces SS volume [ 85 , 87 ] Farm land – Direct use of SS without any treatment Contamination of heavy metals Great source of inorganic/organic substances as fertilizer or to improve soil properties [ 81 , 149 ] Drying 60–93 °C. Spread of waste/SS on open bed of sand and allowed to remain until dry Climate dependent, unstable temperature conditions, cover large land surface, emit odor, heavy metals pollution Performed in natural way, affordable, destroy pathogen, reduce sludge volume [ 136 , 138 ] Dewatering 30–70 °C and 1–300 bar Minimization of water content from SS for its effective disposal This treatment process can't mitigate HMs pollution in SS Improve bio-energy utilization, reduce volume, easy transportation, lessen leachate in landfills, does not contribute to carbon emission [ 61 ] Torrefaction >300 °C Low/slow thermal process in oxygen starving environment Pollution of HMs through different application of torrefied product Produce high amount of biochar, improves solid fuel properties, low energy consumption, short torrefaction time, enhance carbon fixation and hydrophobicity of torrefied material [ 134 , 135 ] Incineration …”