Bioaugmentation-Enhanced Remediation of Crude Oil Polluted Water in Pilot-Scale Floating Treatment Wetlands

Khadeeja Rehman,Samina Iqbal,Imran Amin,Asma Imran,Tanveer Mustafa,Muhammad Saeed,Muhammad Afzal,Muhammad Arslan,Jochen A Müller

doi:10.3390/w13202882

Abstract

Floating treatment wetlands (FTWs) are cost-effective systems for the remediation of polluted water. In FTWs, the metabolic activity of microorganisms associated with plants is fundamental to treatment efficiency. Bioaugmentation, the addition of microorganisms with pollutant-degrading capabilities, appears to be a promising means to enhance the treatment efficiency of FTWs. Here, we quantified the effect of bioaugmentation with a four-membered bacterial consortium on the remediation of water contaminated with crude oil in pilot-scale FTWs planted with Phragmites australis or Typha domingensis. The bacteria had been isolated from the endosphere and rhizosphere of various plants and carry the alkane hydroxylase gene, alkB, involved in aerobic hydrocarbon degradation. During a treatment period of 36 days, FTWs planted with P. australis achieved a reduction in hydrocarbon concentration from 300 mg/L to 16 mg/L with and 56 mg/L without bioaugmentation. In the FTWs planted with T. domingensis, respective hydrocarbon concentrations were 46 mg/L and 84 mg/L. The inoculated bacteria proliferated in the rhizoplane and in the plant interior. Copy numbers of the alkB gene and its mRNA increased over time in plant-associated samples, suggesting increased bacterial hydrocarbon degradation. The results show that bioaugmentation improved the treatment of oil-contaminated water in FTWs by at least a factor of two, indicating that the performance of full-scale systems can be improved at only small costs.

Highlights

The burning of petroleum products still accounts for about one-third of the global society’s energy budget [1]
Pilot-scale Floating treatment wetlands (FTWs) performance was evaluated by examining water quality parameters at 0, 12, 24, and 36 day time points (Figure 2)
The reduction in hydrocarbon concentration, COD, and BOD was significantly lower in the unplanted macrocosms C1 and T1 than in the macrocosms planted with either P. australis or T. domingensis

Summary

Introduction

The burning of petroleum products still accounts for about one-third of the global society’s energy budget [1]. Onshore oil field exploitation alone generates over 5 million m3 per day of polluted water globally [2,3,4]. The polluted water contains a slew of organic and inorganic contaminants such as hydrocarbons, phenols, and heavy metals with high human and ecotoxicological significance [4,5,6]. In particular in LowMiddle-Income Countries (LMIC) with oil production, treatment of the water is limited to storage in so-called evaporation pits as the cheapest approach. Physical and chemical treatment technologies are available but have significant demands on energy input, capital investment, and operation and maintenance cost requirements, and are rarely used in LMIC [7,8]

Methods

Results

Discussion

Conclusion