Abstract
The objective of this study was the development and design of a treatment system at a pilot-plant scale for the remediation of hydrocarbons in industrial wastewater. The treatment consists of a combined approach of absorption and biodegradation to obtain treated water with sufficient quality to be reused in fire defense systems (FDSs). The plant consists of four vertical flow columns (bioreactors) made of stainless steel (ATEX Standard) with dimensions of 1.65 × 0.5 m and water volumes of 192.4 L. Each bioreactor includes a holder to contain the absorbent material (Pad Sentec polypropylene). The effectiveness of the treatment system has been studied in wastewater with high and low pollutant loads (concentrations higher than 60,000 mg L−1 of total petroleum hydrocarbons (TPH) and lower than 500 mg L−1 of TPHs, respectively). The pilot-plant design can function at two different flow rates, Q1 (180 L h−1) and Q2 (780 L h−1), with or without additional aeration. The results obtained for strongly polluted wastewaters showed that, at low flow rates, additional aeration enhanced hydrocarbon removal, while aeration was unnecessary at high flow rates. For wastewater with a low pollutant load, we selected a flow rate of 780 L h−1 without aeration. Different recirculation times were also tested along with the application of a post-treatment lasting 7 days inside the bioreactor without recirculation. The microbial diversity studies showed similar populations of bacteria and fungi in the inlet and outlet wastewater. Likewise, high similarity indices were observed between the adhered and suspended biomass within the bioreactors. The results showed that the setup and optimization of the reactor represent a step forward in the application of bioremediation processes at an industrial/large scale.
Highlights
Hydrocarbons are a large group of organic compounds ubiquitous in air, soil, and water and can be classified into saturated, unsaturated, and aromatic varieties
Immunotoxicity, cardiotoxicity, and carcinogenicity are some of the adverse effects caused by hydrocarbons [1]
The results of this study show that the system under consideration represents an effective technology for removing hydrocarbons from industrial wastewater; this technology is easy to handle and implement
Summary
The complexity of the hydrocarbon molecule will determine its toxicity, its persistence in the environment, and its degradability. The presence of total petroleum hydrocarbons (TPHs) in the soil likely inhibits seed germination and affects plant growth. It was reported that 1.5% TPH is the critical value for plant growth [3]. Some hydrocarbons such as PAHs can act as carcinogenic, mutagenic, and immunosuppressant pollutants. Not all petroleum hydrocarbons and their derivatives possess the same toxicity and recalcitrance and are influenced by different chemical properties such as the complexity of the molecule, water solubility, volatility, etc
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