Pretreatment of alkali/surfactant/polymer (ASP)-flooding produced wastewater by electron beam radiation to improve oil-water separation.

The management of wastewater produced from alkali/surfactant/polymer (ASP) flooding, known for its considerable volume and high emulsion stability, poses a challenge in oilfields globally. This study has demonstrated that ionizing irradiation is a promising pretreatment method for ASP wastewater to improve oil-water separation. After a settling time of 1 h, approximately 69.5% of oil remained in the raw ASP wastewater, while only 20-29% of the oil persisted in the liquid phase following radiation at absorbed doses ranging from 0.1 to 5.0 kGy. A noticeable increase in the size of oil droplets and reduction in turbidity was observed after irradiation. Further analysis revealed that the combination of surfactant, sodium dodecyl sulfate (SDS) and alkali exhibits a synergistic impact, leading to a substantial reduction in interface tension of ASP wastewater. Notably, ionizing irradiation induces several key changes that are crucial for efficient demulsification. The transformation of the wastewater's rheological behavior from pseudoplastics to a Newtonian fluid accompanied by a reduction in viscosity, the increased interfacial tension at both liquid-air and liquid-oil interfaces, along with the degradation of organic components such as partly hydrolyzed polyacrylamide (HPAM) and SDS, all contribute to the coalescence and floatation of oil droplets.

Denitrification of groundwater using PHBV blends in packed bed reactors and the microbial diversity.

In the present study, three kinds of biopolymers, PHBV, PHBV/starch and PHBV/bamboo powder (BP) blends were used as carbon source and biofilm carriers for denitrification in packed bed reactors to remove nitrate from groundwater. Results showed that a fast start-up was obtained in bioreactors filled with both PHBV/Starch and PHBV/BP blends without external inocula and it took more than 3 month for PHBV reactor to reach the same loading rate. The PHBV/BP packed reactor exhibited a better nitrate removal efficiency (87.4 ± 7.0%) and less adverse effects in nitrite accumulation and DOC release (below 0.5 mg NO2N L(-1) and 10.5 mg DOC L(-1) in the effluent) during stable operation. Pyrosequencing analysis demonstrated that bacteria belonging to genus Clostridium in phylum Firmicus, which play the primary role in degrading the biopolymers, are the most dominant (33-15% of the sequences). The predominant species in all samples is related to Clostridium crotonatovorans. All the identified 11 genera of denitrifying bacteria affiliated with phylum Proteobacteria and constituted 30-55% in the representative sequences. The PHBV/BP blend is economically attractive carbon source with good denitrification performance.

Denitrification performance and biofilm characteristics using biodegradable polymers PCL as carriers and carbon source.

In this study, a fixed bed bioreactor filled with biopolymer polycaprolactone (PCL) was developed to remove nitrate from groundwater through denitrification. PCL serves both as carbon source and biofilm carriers. During a long-term operation of 561 d, the performance of the reactor in nitrogen removal, characteristics of biofilm attached to biodegradable carriers, and the hydrolysis and utilization of solid carbon source were studied. With temperatures exceeding 24 °C, the average nitrate concentration in the effluent was lower than 3.7 mg NL(-1), and more than 95% of TN was removed at hydraulic retention time of 3-6h. Nitrite and ammonium remained at low levels (less than 0.32 and 0.78 mg NL(-1), respectively). The calculated PCL amount consumed ranged between 1.6 and 3.7 g PCL g(-1) NO3-N. The FT-IR spectrum of the used PCL indicated the chain scission by hydrolytic degradation. A pyrosequencing analysis of the biofilm showed that genus Diaphorobacter belonging to family Comamonadaceae accounted for most of the sequences. Bacteria of genera Hydrogenophaga, Rhodocyclaceae uncultured and Desulfovibrio were highly enriched in the PCL biofilm. Microelectrode data indicated that the biofilm had an average thickness of around 800 µm and the intensive denitrification activities occurred in the area of 300-500 µm of biofilm with values up to 400 µmol cm(-3)h(-1).

Effects of packing rates of cubic-shaped polyurethane foam carriers on the microbial community and the removal of organics and nitrogen in moving bed biofilm reactors.

The effects of packing rates (20%, 30%, and 40%) of polyurethane foam (PUF) to the removal of organics and nitrogen were investigated by continuously feeding artificial sewage in three aerobic moving bed biofilm reactors. The results indicated that the packing rate of the PUF carriers had little influence on the COD removal efficiency (81% on average). However, ammonium removal was affected by the packing rates, which was presumably due to the different relative abundances of nitrifying bacteria. A high ammonium removal efficiency of 96.3% at a hydraulic retention time of 5h was achieved in 40% packing rate reactor, compared with 37.4% in 20% packing rate. Microprofiles of dissolved oxygen and nitrate revealed that dense biofilm limits the DO transfer distance and nitrate diffusion. Pyrosequencing analysis of the biofilm showed that Proteobacteria, Bacteroidetes and Verrucomicrobia were the three most abundant phyla, but the proportions of the microbial community varied with the packing rate of the PUF carriers.

Comparison of polyurethane foam and biodegradable polymer as carriers in moving bed biofilm reactor for treating wastewater with a low C/N ratio.

This paper presents a comparison between two different materials used as carriers: inert polyurethane (PU) foam and biodegradable polymer polycaprolactone (PCL) particles for the removal of organics and nitrogen from wastewater with a low C/N ratio using moving bed biofilm reactors. The results, during a monitoring period of four months, showed that TOC and ammonium removal efficiency was higher in reactor 2 filled with PU carriers than in reactor 1 filled with PCL carriers (90% and 65% in the former, compared with 72% and 56% in the latter at an hydraulic retention time of 14 h). Reactor 1 showed good behavior in terms of total nitrogen removal as the biodegradable polymer was an effective substrate providing reducing power for denitrification. From three-dimensional excitation-emission matrix analysis, it was shown that the effluent from reactor 1 contained mainly protein-like and soluble microbial product-like substances.