Effects of cell entrapment on growth rate and metabolic activity of mixed cultures in biological wastewater treatment

Entrapped-cells-based anaerobic forward osmosis membrane bioreactor treating medium-strength domestic wastewater: Fouling characterization and performance evaluation

A novel entrapped cells-based-anaerobic forward osmosis membrane bioreactor (E-FOMBR) was developed. Its performance and fouling were investigated in comparison with suspended cells-based-anaerobic forward osmosis membrane bioreactor (S-FOMBR). E-FOMBR and S-FOMBR were operated under the same conditions with two widely used draw solutions (NaCl and (NH₄)₂SO₄). The membrane fouling especially irreversible fouling in S-FOMBR was more severe than that in E-FOMBR regardless of the type of draw solution. The permeate flux of E-FOMBR were 1.79 and 1.85 LMH while those of S-FOMBR were 1.49 and 1.14 LMH with NaCl and (NH₄)₂SO₄ as draw solutions, respectively. More deterioration of biological activity (suggested by lower organic removal) due to accumulation of salt was observed in S-FOMBR compared to E-FOMBR. Proteobacteria dominated in both FOMBRs but was more abundant in E-FOMBR than S-FOMBR. The superiority of E-FOMBR over S-FOMBR included higher and stable system performance, higher flux, and longer operation time.

Performance and kinetics of triclocarban removal by entrapped Pseudomonas fluorescens strain MC46

This study investigated removal of triclocarban (TCC) from contaminated wastewater by Pseudomonas fluorescens strain MC46 entrapped in barium alginate. Appropriate entrapped cell preparation conditions (cell-to-entrapment material ratio and cell loading) for removing TCC were examined. The highest TCC removal by the entrapped and free cell systems at the initial TCC concentration of 10 mg/L was 72 and 45%, respectively. TCC was degraded to less toxic compounds. Self-substrate inhibition was found at TCC concentration of 30 mg/L. The kinetics of TCC removal by entrapped and free cells fitted well with Edwards model. Scanning and transmission electron microscopic observations revealed that entrapment matrices reduced TCC-microbe contact, which lessened TCC inhibition. A live/dead cell assay also confirmed reduced microbial cell damage in the entrapped cell system compared to the free cell system. This study reveals the potential of entrapment technology to improve antibiotic removal from the environment.

Entrapped cells-based-anaerobic membrane bioreactor treating domestic wastewater: Performances, fouling, and bacterial community structure

A laboratory scale study on treatment performances and fouling of entrapped cells-based-anaerobic membrane bioreactor (E-AnMBR) in comparison with suspended cells-based-bioreactor (S-AnMBR) treating domestic wastewater was conducted. The difference between E-AnMBR and S-AnMBR was the uses of cells entrapped in phosphorylated polyvinyl alcohol versus planktonic cells. Bulk organic removal efficiencies by the two AnMBRs were comparable. Lower concentrations of suspended biomass, bound extracellular polymeric substances and soluble microbial products in E-AnMBR resulted in less fouling compared to S-AnMBR. S-AnMBR provided 7 days of operation time versus 11 days for E-AnMBR before chemical cleaning was required. The less frequent chemical cleaning potentially leads to a longer membrane life-span for E-AnMBR compared to S-AnMBR. Phyla Proteobacteria, Chloroflexi, Bacteroidetes and Acidobacteria were dominant in cake sludge from both AnMBRs but their abundances were different between the two AnMBRs, suggesting influence of cell entrapment on the bacteria community.

Removal of environmental estrogens by bacterial cell immobilization technique

Contamination of steroidal estrogens in the environment has raised a great public concern, and therefore, developing an effective method for removal of trace amount of environmental estrogens is necessary. In this study, two estrogen-degrading bacteria were isolated from activated sludge and were identified as strain Sphingomonas sp. AHC-F and strain Sphingobium sp. AX-B. They were capable of utilizing estrone (E1) and 17ß-estradiol (E2) as sole carbon and energy source. Cell immobilization technique was applied to these two estrogen-degrading bacteria. Confocal laser-scanning microscopy images with live and dead staining of entrapped bacterial cells showed that most bacteria were present inside the porous structure and were mostly viable after immobilization procedures. Batch estrogen degradation study showed that immobilized strains AHC-F and AX-B could effectively degrade 2 mg/L of E2 and its metabolite E1. Immobilized bacteria column reactors using pure culture of strain AHC-F were set up for continuous-flow removal of 850 ng/L of E2 in the influent. The removal efficiency of E2 and equivalent estrogenic quantity of E2 (EEQ) could achieve 94 and 87% under 12 h hydraulic retention time (HRT), respectively. Increasing HRT could further improve the removal efficiency of EEQ. When the HRT increased to 72 h, the effluent concentrations of E2 and E1 were not detectable by gas chromatography-mass spectrometry. Our results also proved that most of the estrogen removal was due to biodegradation. This study has demonstrated the potential use of immobilized bacteria technique for the removal of environmental estrogens.

Simulated sugar factory wastewater remediation kinetics using algal-bacterial raceway reactor promoted by polyacrylate polyalcohol

The remediation kinetics of simulated sugar factory wastewater (SFW) using an algal-bacterial culture (ABC) of Chlorella vulgaris in association with Pseudomonas putida in a raceway reactor was found to be enhanced by 89% with the addition of 80ppm of copolymer Polyacrylate polyalcohol (PAPA). This was achieved by efficient suspension of the ABC throughout the water body maintaining optimum pH and dissolved oxygen that led to rapid COD removal and improved algal biomass production. The suspension of the ABC using the co-polymer PAPA maintained a DO of 8-10mgl(-1) compared to 2-3mgl(-1) when not suspended. As a result, the non-suspended ABC only achieved a 50% reduction in COD after 96h compared to a 89% COD removal using 80ppm PAPA suspension. In addition, the algae biomass increased from 0.4gl(-1)d(-1) for the non-suspended ABC to 1.1gl(-1)d(-1) when suspended using 80ppm PAPA.

Marine carbohydrates of wastewater treatment

Our natural heritage (rivers, seas, and oceans) has been exploited, mistreated, and contaminated because of industrialization, globalization, population growth, urbanization with increased wealth, and more extravagant lifestyles. The scenario gets worse when the effluents or contaminants are discharged directly. So wastewater treatment is a very important and necessary in nowadays to purify wastewater before it enters a body of natural water, or it is applied to the land, or it is reused. Various methods are available for treating wastewater but with many disadvantages. Recently, numerous approaches have been studied for the development of cheaper and more effective technologies, both to decrease the amount of wastewater produced and to improve the quality of the treated effluent. Biosorption is an emerging technology, which uses natural materials as adsorbents for wastewater treatment. Low-cost adsorbents of polysaccharide-based materials obtained from marine, such as chitin, chitosan, alginate, agar, and carrageenan, are acting as rescue for wastewater treatment. This chapter reviews the treatment of wastewater up to the present time using marine polysaccharides and its derivatives. Special attention is paid to the advantages of the natural adsorbents, which are a wonderful gift for human survival.

Effects of cell entrapment on nucleic acid content and microbial diversity of mixed cultures in biological wastewater treatment

The effects of entrapment on nucleic acid content and microbial diversity of mixed cultures in biological municipal wastewater treatment were investigated. Deoxyribonucleic acid content increased 1.6-5.5 times more in alginate entrapped cells than in free and polyvinyl alcohol (PVA) entrapped cells. PVA entrapment resulted in 1.1- to 5.9-fold more increases in ribonucleic acid content compared to that experienced by free and alginate entrapped cells. Entrapment in carrageenan changed the bacterial community structure more than the alginate and PVA entrapments (35-80% versus 0-35%) as determined by single-strand conformation polymorphism analyses. The change in the bacterial community structure of alginate entrapped cells was less time dependent than that of PVA entrapped cells. This study enhances understandings on the physiology of entrapped cells and their community evolution in wastewater treatment environments.