Performance of three small-scale wastewater treatment plants. A challenge for possible re use

Abstract

The study focused on the assessment of the performance of three WWTPs in Greece by the estimation of the microbiological and chemical quality of influent and effluent sewage. Physicochemical parameters were recorded (temperature, pH, COD, BOD, suspended solids, conductivity), and meteorological data were collected (air temperature, rain). Microbiological parameters were analyzed (Escherichia coli, total coliforms, bacteriophages, Salmonella, human adenoviruses, Candida, Pseudallescheria boydii, helminths, parasites Cryptosporidium ssp., and Giardia spp.). Statistically significant correlations among the various aforementioned parameters were investigated, in an attempt to propose appropriate processing performance indicators. Furthermore, the study aimed to assess current joint ministerial decision (JMD) on wastewater reuse, for irrigation purposes; to evaluate its practicability and its potential for public health protection. In the vast majority, outlet samples from all three studied WWTPs were not appropriate for irrigation reuse purposes based on BOD50 and suspended solids limit values, set by the current JMD, for both limited and unrestricted irrigation applications. Reductions for E. coli, total coliforms, and bacteriophages were found to range between 2-3, 1.5-2.5, and 2-4 log10 values, respectively. Salmonella spp. was detected in outlet sewage samples from Patra (PAT), Arachova (ARH), and Livadeia (LEV), at 23% (3/13), 33% (4/12), and 38% (5/13), respectively. Molds were detected at 92.3% (12/13), 100% (13/13), and 91.6% (11/12), respectively, while Candida was found at 85% (11/13), 67% (8/12), and 46% (6/13). A high prevalence of Pseudallescheria boydii, in outlet samples from all studied WWTPs is an important public health issue, which underlines the need for further studies on this emerging fungal pathogen in wastewater reuse applications. Pseudallescheria boydii was found at 85% (11/13), 67% (8/12), and 46% (6/13), respectively. Helminths were found in both inlet and outlet samples, of all studied WWTPs, at 100%. Human adenoviruses, were detected at high percentages in outlet samples at 76.9% (10/13), 92.3% (12/13), 84.6% (11/13), respectively, while no influence of UV irradiation was recorded on the entry and exit loads of human adenoviruses. No influence of meteorological parameters was found on the microbiological and chemical parameters, with the exception of a weak positive correlation between environmental temperature and bacteriophages. A moderate positive correlation was found between BOD and suspended solids, bacteriophages, and total coliforms, bacteriophages and E. coli, and bacteriophages and adenoviruses. A significant positive correlation was found between total coliforms and E. coli, COD and BOD, and suspended solids and COD. No correlations were proved between human pathogens and bacterial indicator parameters. Collectively, our findings underlined the unsuitability of the current JMD on wastewater reuse in Greece, or public health protection. The study is expected to support the deve...

Study on the efficiency of sequential batch reactor (SBR)-based sewage treatment plant

“…Highly significant positive correlation (r = 0.728; P < 0.01) of COD with TSS shows that increase in TSS increases the COD and TSS is composed of both organic and inorganic substances. Kokkinos et al (2015) also reported positive correlation between COD and TSS.…”

Environmental and Adaptive Changes Necessitate a Paradigm Shift for Indicators of Fecal Contamination

“…Over 200 enteric viruses known to infect humans are considered pathogens because of their high resistance to treatment processes and their low infectious doses (35). To appropriately eliminate these viruses, it is necessary to use tertiary treatment processes involving chlorine, ozone, and exposure to UV light in drinking water treatment plants and WWTPs (36)(37)(38). However, due mainly to cost issues, many of the rather complex treatments are not always available in most DWTPs or drinking water treatment plants worldwide.…”

“…Taking into account that most pathogenic viruses are also resistant to several of the most commonly used water treatment technologies (disinfection, heating, pressure, and low pH [56,199]), it is essential that the treatment of water for human consumption or water reuse be effective and regulated (200). However, some studies indicate that these treatments are sometimes not completely effective in eliminating the enteric viruses discussed here, either in drinking water or wastewater (38,56,189,190,201). Moreover, about 90% of all wastewater is released into the environment without complete disinfection.…”

Deteção de vírus entéricos em amostras de água natural superficial e de água para consumo humano

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