Influence of Different Pretreatments on Anaerobically Digested Sludge Characteristics: Suitability for Final Disposal

Abstract

The debate on sludge recycling and disposal has been recently a target of growing interest due to the expressed concern about the potential risks of its agricultural use on human health and the environment. This fact has led to revisions in government policy and regulations and many novel treatment processes have been proposed in order to make the recycling and reuse of sewage sludge sustainable. In this work, the use of some pretreatments (alkaline, thermal, and ozonation) combined with conventional anaerobic digestion has been assessed on digested sludge quality in terms of pathogens, dewatering properties, heavy metals, and organic pollutants. All pretreatments proved to be efficient to reach the requirements proposed in the Working Document on Sludge prepared by the European Commission (CEC, Council Directive of 27 April 2000 on Working Document on Sludge-third draft. Brussels: European Commission DG Environment. Retrieved from http:// ec.europa.eu/environment/waste/sludge/pdf/sludge_en. pdf, 2000a) and also those established by the U.S. Environmental Protection Agency (EPA, Standards for the disposal and utilization of sewage sludge, part 503.

Influence of feed characteristics on the removal of micropollutants during the anaerobic digestion of contaminated sludge

“…According to this view, thermal pre-treatment should decrease micropollutant biodegradation, as a result of a decrease in the bioavailability. The fact that no impact or, indeed, a negative impact was previously detected on NP [35], pharmaceuticals and personal care products [26] and linear alkylbenzene sulphonates [42] tend to corroborate the hypotheses. The poorer removal of micropollutants after thermal pre-treatment observed in this study is thus consistent with the previously published data and might be explained by lower bioavailability after such pretreatment.…”

Application of physico-chemical pretreatment methods to enhance the sludge disintegration and subsequent anaerobic digestion: an up to date review

“…The pretreatment of sludge with lime at pH 11 or higher was observed to be efficient to kill the pathogens . Carballa et al (2009) also observed the significant removal ([85%) of total coliforms and fecal streptococcus by adding the lime up to pH 12 for 24 h reaction time.…”

“…According to Chu et al (2008), about 80% microorganism (activated sludge micro-fauna) inactivation was observed in micro-bubble ozonation system at an ozone dose of 0.02 g O 3 /g TSS for 20 min contact time. Carballa et al (2009) applied an ozone dose of 20 mg O 3 /g TSS for 2 h for the treatment of combined sludge (primary and WAS). They observed that the ozonation is not capable to eliminate the Salmonella spp.…”

“…Carballa et al (2009) reported that the numbers of pathogens was decreased significantly after thermal pretreatment of sludge (at 130°C for 1 h). The numbers of TC, E. coli, F. streptococci (MPN/gTS), C. prefringens, were 41, 15, 24 and 1,700 CFU/gTS, respectively.…”

Multivariate analysis of sludge disintegration by microwave–hydrogen peroxide pretreatment process

“…1). In particular, the results suggest that, to achieve optimal conditions generally, focus should be placed primarily on solubilization conducted under mild conditions (i.e., H 2 O 2 ∈ [1.4, 2.0]; pH ∈ [8,10]). Moreover, the model acquired from the response surfaces discussed in the previous sections provides an effective strategy to optimize the microwave/hydrogen peroxide/pH pretreatment process for multiple objectives, including anaerobic digestion, sludge leaching, and nutrient recovery.…”