Evaluation of microbiological and physicochemical indicators for wastewater treatment

Abstract

The quality control of wastewater treatments was monitored using selected novel and classical physicochemical and microbiological indicators, and the associations of the treatments with the effluents was analyzed. The microbiological indicators monitored were heterotrophic plate count (HPC), total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS), sulfite-reducing clostridia (SRC), Pseudomonas aeruginosa, and Salmonella spp. The stages of wastewater treatment also were evaluated through determination of ammonia; biological oxygen demand (BOD(5)); chemical oxygen demand (COD); chloride; conductivity; suspended dissolved and total solids; fats; nitrate, nitrite, and total nitrogen; pH; phosphate and total phosphorus. Additional indicators included the Escherichia coli growth inhibition (IGEC) bioassay for assessing whole effluent toxicity, spectral determinations between wavelengths (lambda) 190-650 nm, and total (TP) and soluble (SP) protein contents. Of the more common physicochemical parameters, only BOD(5), COD, suspended and total solids, and fats showed a statistically significant reduction between raw water and effluent; for the microbiological indicators, significant reduction was seen only for HPC, FC, and Ps. aeruginosa. We suggest that determinations of Ps. aeruginosa be commonly used as an indicator of wastewater quality. Spectral analysis--most notably the values of absorbance at 225, 255, and 295 nm-revealed a statistically significant correlation with several physicochemical parameters. Statistical analysis of SP and TP values showed them to be good indicators of contamination. The quantitative study of Salmonella spp. and the results of the IGEC bioassay show the need for close control of infectious and toxic risks in wastewater and effluents.

Molecular typing, antibiotic resistance, virulence gene and biofilm formation of different Salmonella enterica serotypes

“…Furthermore, wastewater is often contaminated by urban wastewater, by effluents of meat industries and by wastewater from livestock ranches (Espigares et al, 2006). Several studies showed that the conventional wastewater treatment process does not guarantee their total removal (Howard et al, 2004). The survival of Salmonella even with treatment implies the possibility of selection and dissemination of the most resistant strains.…”

Serotyping and molecular typing of Salmonella species isolated from wastewater in Nsukka, Nigeria

“…This is in consonance with the work done by El Hussein et al (2012) in Khartoum State, Sudan, who reported an occurrence of 11.09% of Salmonella species in wastewater. Conversely, a report by Howard et al (2004) showed that municipal wastewater having undergone an activated sludge process continued to bear Salmonella at high concentration; the treated water yielded a most probable number (MPN) of 45/100 ml. Also, El-Taweel (1994) found that Salmonella spp.…”

Salmonella in Wastewater: Identification, Antibiotic Resistance and the Impact on the Marine Environment

“…An activated sludge treatment process remains unable to totally remove Salmonella [9,12]. Koivunen et al have also shown that activated sludge process coupled with phosphorus precipitation followed by a secondary settling or coupled with denitrification-nitrification fails to remove Salmonella from municipal wastewater [1].…”

“…Previous works [1,[9][10][11][12][13] have studied the presence of Salmonella in wastewater but they stay insufficient to provide enough information on the diversity and the antibiotic resistance profiles of Salmonella. This makes transmission of Salmonella via wastewater, its impact on the environment and the origin of contamination poorly understood.…”