Petroleum-contaminated soil: using sonolysis to improve mineralization and biodegradation potential of Fenton reaction and ozonolysis process.

The degradation efficiency of the Fenton reaction or ozonolysis (O3) to treat soil contaminated by crude petroleum was studied in association with the sonolysis process. To quantify oxidation efficiency, total organic carbon (TOC) and chemical oxygen demand (COD) were measured, while biochemical oxygen demand (BOD5) was measured to estimate biodegradation potential. TOC removal efficiency ranged from 9 to 52% to the Fenton reaction without sonolysis, and 18% and 78% with sonolysis for reagent concentrations of 1% H2O2-100 mM Fe2+ and 20% H2O2-1 mM Fe2+, respectively. For ozonolysis (after 10 and 60 min of treatment), the reduction in TOC ranged from 9 to 43% without sonolysis and 15 to 61% with sonolysis. The Fenton reaction without sonolysis increased the biodegradability in relation to the non-oxidized sample by 6% (1% H2O2-100 mM Fe2+) and 26% (20% H2O2-1 mM Fe2+), and with sonolysis the corresponding values were 13% and 42%, respectively. The biodegradation potential under ozonolysis without sonolysis increased from 0.18 (10 min of treatment) to 0.38 (30 min of treatment), and with sonolysis these values were 0.26 and 0.58, respectively. Optimization of the remediation processes is essential to determine sequential treatment order and efficiency.

Influence of desorption process and pH adjustement on the efficiency of O3, O3/H2O2 and O3/UV treatment of water and soil samples contaminated by crude petroleum.

The influence of the pH and the contaminant desorption/emulsification on ozone (O3), ozone-hydrogen peroxide (O3/H2O2) and ozone-photolysis (O3/UV) oxidation reactions were performed to treat crude petroleum (CP) contaminated soil and water samples. Oxidation efficiency is also related to both free radicals formation in reaction medium (which is dependent of the pH), and contaminant availability (which is dependent of the compounds solubilization or desorption processes). Thus, batch basic processes of O3/H2O2 or O3/UV were improved with sonication system and surfactant addition. In the case of O3/H2O2 process, the reactions were performed at adjusted (pH = 11) and natural pH (free pH= 4-5). The effectiveness of the improved advanced oxidation processes were evaluated through the time-course analysis of the chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and total organic carbon (TOC) values. For both improved treatment processes, CP-contaminated water samples displayed higher values for TOC removal and BOD5/COD ratios than CP-contaminated soil samples. The O3/H2O2 process provided better results than the O3/UV process regarding degradation efficiency, but the former is associated with higher treatment costs due to H2O2 consumption. Overall, oxidation treatment processes increase their efficiencies when reactions are carried out associated with solubilization and desorption systems promoted by sonication/surfactant action.

Small hazardous waste generators in developing countries: use of stabilization/solidification process as an economic tool for metal wastewater treatment and appropriate sludge disposal.

The aim of this study was to propose a profitable destination for an industrial sludge that can cover the wastewater treatment costs of small waste generators. Optimized stabilization/solidification technology was used to treat hazardous waste from an electroplating industry that is currently released untreated to the environment. The stabilized/solidified (S/S) waste product was used as a raw material to build concrete blocks, to be sold as pavement blocks or used in roadbeds and/or parking lots. The quality of the blocks containing a mixture of cement, lime, clay and waste was evaluated by means of leaching and solubility tests according to the current Brazilian waste regulations. Results showed very low metal leachability and solubility of the block constituents, indicating a low environmental impact. Concerning economic benefits from the S/S process and reuse of the resultant product, the cost of untreated heavy metal-containing sludge disposal to landfill is usually on the order of US$ 150-200 per tonne of waste, while 1tonne of concrete roadbed blocks (with 25% of S/S waste constitution) has a value of around US$ 100. The results of this work showed that the cement, clay and lime-based process of stabilization/solidification of hazardous waste sludge is sufficiently effective and economically viable to stimulate the treatment of wastewater from small industrial waste generators.

Textile sludge application to non-productive soil: physico-chemical and phytotoxicity aspects.

As part of an assessment study on the risk of spreading textile sludge onto non-productive soil, the sorption behaviour of some sludge-metal constituents [Cr(VI), Cu(II), Pb(II), and Zn(II)] in the soil was studied. In addition, the sludge stabilization effect was evaluated by the biodegradation of organic compounds and phytotoxicity tests. Metal-soil sorption was assessed using soil columns and by sorption isotherms (i.e., Freundlich and Langmuir). In relation to the phytotoxicity of Eruca sativa L., there was a biomass inhibitory effect for the fresh sludge and a biomass stimulant effect for the stabilized sludge. Thus our results show that after stabilization, the tested loading ratio of 33% sludge: 67% soil (v/v) (equivalent to 85 Mg ha(-1)) did not significantly increase the risk of groundwater contamination since only small amounts of metals applied to the soil underwent percolation and almost all the organic compounds were degraded.