Analysis of heavy metals during composting of the tannery sludge using physicochemical and spectroscopic techniques

Abstract

The major limitation of direct application of tannery sludge compost in agriculture is the total heavy metal contents and their bioavailability to the soil-plant system. This study focused on the heavy metal characterization and the influence of changing the physicochemical properties of the medium throughout the composting on the concentrations, bioavailability or chemical forms of Cr, Cu, Zn, Pb and Cd in tannery sludge. The study shows that throughout the 60 days of composting, physicochemical analysis and Fourier-transformed infrared (FTIR) spectroscopic characterization show that all parameters elaborated and reached relatively stable levels reflecting the stability and maturity of the final product, and revealed the biodegradation of components that can be easily assimilated by microorganism. The C/N ratio reaches the optimal range of stable compost; inorganic nitrogen is transformed into stable organic forms. The total concentration of Cr, Zn, Cu, Pb and Cd is very low rendering final compost acceptable for agricultural use. The germination index for both Chinese cabbage and lettuce was 97% after 60 days of composting, showing that the final compost was not phytotoxic. Furthermore, in using a sequential extraction method in sludge compost at different phases of treatment, a less than 2% of metals bound to bioavailable fractions X-(KNO(3)+H(2)O). A large proportion of the heavy metals were associated to the residual fraction (75-85%) and more resistant fractions to extraction X-NaOH, X-EDTA, X-HNO(3) (15-25%). Mobile fractions of metals are poorly predictable from the total content. Bioavailability of all fractions of elements tends to decrease.

Phytoremediation of chlorobenzenes in sewage sludge cultivated with Pennisetum purpureum at different times

“…These data are consistent with those of Haroun et al (2009), who observed that during the sewage sludge mineralization stage there is a substantial increment of contaminants.…”

Vitrification as an alternative to landfilling of tannery sewage sludge

“…Numerous studies have been conducted all over the world in order to finally solve the problem of tannery sewage sludge and tannery waste in general. The use of methods such as co-digestion (Zupancic and Jemec, 2010) or composting (Haroun et al, 2009) is strictly dependent on chromium concentration, which represents the main limitation. As noted by Altas (2009), chrome concentration as low as 27 mg/l negatively affects methane production during co-digestion, which means that the amount of co-digested sewage sludge is limited.…”

Avaliação Da Biodegradação De Serragem De Rebaixamento De Couro Curtido Ao Cromo

“…A composição do estrume suíno pode variar conforme inúmeros fatores, como a alimentação dos animais, condições de coleta, períodos de armazenamento, entre outros. No caso do lodo de ETE os valores de CO e NTK são aproximados aos obtidos por outros autores, como Haroun et al (2009). Os teores de cromo encontrados na literatura são de grande divergência, que pode ocorrer de acordo com as etapas realizadas no processamento do curtume.…”