Bioremediation of Sewage Sludge by Composting

Abstract

Sewage sludge used as soil organic amendment can positively affect soil physical, chemical, and biological properties. This organic material may be a solution for improving the low organic matter content of Mediterranean soils. However, the addition of sewage sludge to soils have not always shown positive effects, probably due to the particular characteristics of the residues concerned: high heavy metal or phytotoxic substance content, excess of labile organic matter, pathogenic microorganisms, etc. Composting process can be a useful tool to eliminate some of these problems. In the present work, a sewage sludge mixed with wood shaving as bulking agent has been composted. During this process, a decrease of organic matter fractions due to organic matter mineralization was observed. Fresh sewage sludge contained high numbers of pathogen microorganisms but when this material was submitted to composting process microorganisms decreased to suitable level. Organic compounds 957 such as pesticide residues can also be partially or totally degraded by microorganisms during composting process, prometrine and terbutrine being the most recalcitrant compounds. Composting process eliminated phytotoxic compounds contained in sewage sludge, permitting an adequate germination index.

Evolution of chemical and biological characterization during agitated pile composting of flower waste

“…The buffering capacity of humus and volatilization of ammonia result in a slight decrease in pH value. Similar results were reported for organic waste composting (Kalamdhad and Kazmi 2009;Mena et al 2003). The final pH value between 6 and 8 shows the maturity of the compost (Varma and Kalamdhad 2014a).…”

Changes in chemical and biological parameters during co-composting of anaerobically digested sewage sludges with lignocellulosic material

“…Such a trend due to organic matter mineralization is reported by several authors. [12,15,25,26] Potassium content Both the starting mixtures exhibited a high total K content (5.6 and 4.4 g Kg -1 in mixtures A and B respectively) which increased to 7.1 and 8.2 g Kg -1 . Although K is an important nutrient, its concentration in compost is seldom reported.…”

“…Although K is an important nutrient, its concentration in compost is seldom reported. A compost obtained from sewage sludge mixed with woodchips exhibited a K concentration of 2.3 g Kg -1 [15] while about 10 mg Kg -1 K was found in a vermicompost of organic wastes. [25] K concentration is largely dependent on the starting materials.…”

“…An increase in EC usually takes place during composting as a result of the release of salts due to the mineralization of organic material. The range of variation of this parameter is dependent on the nature of the initial feedstocks: increases from about 600 to 800 µS cm -1 during composting of sheep manure and straw, [14] from 1166 to 2230 µS cm -1 during composting of sewage sludges mixed with wood shavings, [15] from 900 to 1600 µS cm -1 during composting of pig manure and sawdust, and from about 2000 to 3000 µS cm -1 during composting of food waste [16] were reported. In contrast, Li et al [17] observed a decrease from 4360 to 2750 µS cm -1 during composting of a mixture of sewage sludges, pig manure, and sawdust.…”

“…[13] However, in the case of sewage sludges based mixtures several studies report a low initial C/N ratio and a reduced change in this parameter during the process in agreement with our results. [15,18,20,23] Several studies have been conducted in order to verify the effect of the initial C/N ratio on the composting process by using different compositions of starting materials. Eiland et al [24] observed that low initial C/N ratios caused a fast degradation of fibres during the first three months of composting of straw and pig manure (hemicellulose: 50-80%, cellulose: 40-60%).…”