Municipal Wastewater Treatment Plant Effluents Research Articles

Peracetic acid (PAA) disinfection of primary, secondary and tertiary treated municipal wastewaters

The efficiency of peracetic acid (PAA) disinfection against enteric bacteria and viruses in municipal wastewaters was studied in pilot-scale. Disinfection pilot-plant was fed with the primary or secondary effluent of Kuopio municipal wastewater treatment plant or tertiary effluent from the pilot-scale dissolved air flotation (DAF) unit. Disinfectant doses ranged from 2 to 7 mg/l PAA in the secondary and tertiary effluents, and from 5 to 15 mg/l PAA in the primary effluents. Disinfection contact times were 4–27 min. Disinfection of secondary and tertiary effluents with 2–7 mg/l PAA and 27 min contact time achieved around 3 log reductions of total coliforms (TC) and enterococci (EC). PAA disinfection also significantly improved the hygienic quality of the primary effluents: 10–15 mg/l PAA achieved 3–4 log reductions of TC and EC, 5 mg/l PAA resulting in below 2 log reductions. F-RNA coliphages were more resistant against the PAA disinfection and around 1 log reductions of these enteric viruses were typically achieved in the disinfection treatments of the primary, secondary and tertiary effluents. Most of the microbial reductions occurred during the first 4–18 min of contact time, depending on the PAA dose and microorganism. The PAA disinfection efficiency remained relatively constant in the secondary and tertiary effluents, despite of small changes of wastewater quality (COD, SS, turbidity, 253.7 nm transmittance) or temperature. The disinfection efficiency clearly decreased in the primary effluents with substantially higher microbial, organic matter and suspended solids concentrations. The results demonstrated that PAA could be a good alternative disinfection method for elimination of enteric microbes from different wastewaters.

Sources of Pathogenic Microorganisms and Their Fate during Land Application of Wastes

ABSTRACTThe hazards associated with pathogens in land‐applied animal and human wastes have long been recognized. Management of these risks requires an understanding of sources, concentrations, and removal by processes that may be used to treat the wastes; survival in the environment; and exposure to sensitive populations. The major sources are animal feeding operations, municipal wastewater treatment plant effluents, biosolids, and on‐site treatment systems. More than 150 known enteric pathogens may be present in the untreated wastes, and one new enteric pathogen has been discovered every year over the past decade. There has been increasing demand that risks associated with the land treatment and application be better defined. For risks to be quantified, more data are needed on the concentrations of pathogens in wastes, the effectiveness of treatment processes, standardization of detection methodology, and better quantification of exposure.

PHOSPHATE EQUILIBRIUM BETWEEN STREAM SEDIMENTS AND WATER: POTENTIAL EFFECT OF CHEMICAL AMENDMENTS

Sediments often play an important role in the temporary storage and release of phosphorus (P) in streams, especiallystreams receiving municipal wastewater treatment plant (WWTP) effluent. The objective of this study was to evaluatesediment-aqueous phase P equilibrium in four Ozark streams, and to determine the effect of alum (Al2(SO4)3) and calciumcarbonate (CaCO3) on stream sediment-P interactions and content of exchangeable P. Stream physicochemical propertieswere significantly affected by the effluent discharge from the WWTPs; of particular interest to this study was that the increasein P concentrations varied greatly among streams. Phosphorus inputs from WWTP significantly increased sedimentequilibrium P concentrations (sediment-EPC0) and readily exchangeable sediment-bound P, while decreasing the Pbuffering capacity of stream sediments. Sediment-EPC0 values were as great as 7 mg L-1 downstream from one WWTP,suggesting that sediments are a transient storage pool of P and may release P back into the stream system when P inputs fromthe WWTP are reduced. The addition of alum and CaCO3 significantly reduced the sediment-EPC0 and readily exchangeableP, while increasing the ability of sediments to buffer increasing P loads.

Aquatic ecotoxicology of fluoxetine

Recent studies indicate that the pharmaceutical fluoxetine, a selective serotonin reuptake inhibitor, is discharged in municipal wastewater treatment plant effluents to surface waters. Few data on environmental fluoxetine exposure and hazard to aquatic life are currently available in the literature. Here, we summarize information on fluoxetine detection in surface waters and review research on single-species toxicity test, Japanese medaka ( Oryzias latipes) reproduction and endocrine function, and freshwater mesocosm community responses to fluoxetine exposure. Based on results from our studies and calculations of expected introduction concentrations, we also provide a preliminary aquatic risk characterization for fluoxetine. If standard toxicity test responses and a hazard quotient risk characterization approach are solely considered, little risk of fluoxetine exposure may be expected to aquatic life. However, our findings indicate that: (1) the magnitude, duration and frequency of fluoxetine exposure in aquatic systems requires further investigation; (2) mechanistic toxicity of fluoxetine in non-target biota, including behavioral responses, are clearly not understood; and (3) an assessment of environmentally relevant fluoxetine concentrations is needed to characterize ecological community responses.

An Ecological Risk Assessment of Nonylphenol and Its Ethoxylates in the Aquatic Environment

Nonylphenol ethoxylates (NPEs) are a group of surfactants that are widely used for industrial, commercial, institutional and household purposes in Canada. Ethoxylation of nonylphenol (NP) occurs upon reaction with ethylene oxide, producing NPEs, although NP is also used in the production of the antioxidant tris(nonylphenol)phosphite. NP and NPEs are not produced naturally, and the primary route of environmental exposure to NP and NPEs is via textile mill, pulp and paper mill and municipal wastewater treatment plant effluents. NPEs occur as complex mixtures and are described by the average ethoxylate chain length, which ranges from 1 to 100. The environmental fate of NPEs is strongly dependent on the effluent and, the degree and type of treatment to which the effluent is subjected. An ecological risk assessment was performed to determine if exposure to NP and NPEs results in effects on the Canadian environment, based on current use patterns. The Canadian ecological risk assessment found that adverse effects on aquatic organisms are likely, although assumptions were made with respect to appropriate dilution factors.

Use of chlorophyll fluorescence of Closterium ehrenbergii and Lemna gibba for toxic effect evaluation of sewage treatment plant effluent and its hydrophobic components

In this study fluorometric methods using an alga, Closterium ehrenbergii, and a higher plant, Lemna gibba, were employed to evaluate the toxicity of sewage treatment plant (STP) effluent and its hydrophobic components. Fluorescence parameters such as the operational photosystem II quantum yield at steady state of electron transport, the nonphotochemical quenching, and the complementary area were modified in the presence of hydrophobic components, particularly with C. ehrenbergii. It was found that C. ehrenbergii was a suitable species to be used in a hydrophobic components bioassay, since this alga was 400 times more sensitive than L. gibba to hydrophobic components. Results indicate that hydrophobic STP effluent components are less toxic as a constituent of the STP effluent than when they are extracted from the effluent. We also demonstrated here that in addition to the growth inhibition test, fluorometric methods can be usefully employed in bioassays for the toxic effect evaluation of pollutants present in municipal wastewater treatment plant effluents.

Elimination of enteric bacteria in biological–chemical wastewater treatment and tertiary filtration units

The occurrence and removal of salmonellae and faecal indicators in four conventional municipal wastewater treatment plants (MWTP) were investigated. In addition, we tested the efficiency of a semi-technical scale biological nutrient removal process and three pilot-scale tertiary filtration units in microbial removal. All influent samples collected from MWTPs contained salmonellae from 93 to 11 000 MPN/100 ml and indicator bacteria from about 10 7 to 10 8 CFU/100 ml. The reductions in salmonella numbers achieved in full-scale biological–chemical wastewater treatment and semi-technical scale biological nutrient removal processes were usually between 94% and virtually 100% (99.9%) and indicator bacteria reductions between 2 and 3 log units. Microbial numbers in MWTP effluents could be modelled as a function of effluent residual organic matter, suspended solids and total phosphorus concentrations. Pilot-scale tertiary treatment by rapid sand contact filter, chemical contact filter and biological–chemical contact filter reduced salmonella numbers below the detection limit and faecal coliform numbers on average by 99%, 39% and 71%, respectively. A total of 32 Salmonella serovars were identified among 197 Salmonella isolates from municipal wastewaters. Of the isolates, 32% were resistant to nalidixic acid, indicating reduced sensitivity to ciprofloxacin, the drug of choice in the treatment of salmonellosis. In addition, 18% of the isolates were multiresistant. Our results, especially antibiotic resistant Salmonella strains, indicate that conventional municipal wastewater treatment without efficient tertiary treatment, like filtration or disinfection, may constitute a risk for public health.

A comparison of stream biological responses to discharge from wastewater treatment plants in high and low population density areas

The ultimate purpose of this study was to identify broad relationships that may have relevance for the risk assessment of chemicals and materials that are discharged to receiving streams via municipal wastewater treatment plant (WWTP) effluents (e.g., consumer product ingredients). The effects of municipal wastewaters occurring in high population density (>500 persons per square mile, urban) and low population density (<500 persons per square mile, rural) environments were determined via analysis of biological, habitat, and water chemistry data collected both immediately upstream and downstream of 221 WWTPs in Ohio, USA. Several biological and chemistry indicators demonstrated poorer water quality in urban areas compared to rural areas. After considering the effect of river size, adverse effects downstream of WWTPs for both fish and macroinvertebrate communities were clearly identified for only urban areas. These data indicate that WWTP potency may be greater in urban areas compared to rural areas.

A COMPARISON OF STREAM BIOLOGICAL RESPONSES TO DISCHARGE FROM WASTEWATER TREATMENT PLANTS IN HIGH AND LOW POPULATION DENSITY AREAS

The ultimate purpose of this study was to identify broad relationships that may have relevance for the risk assessment of chemicals and materials that are discharged to receiving streams via municipal wastewater treatment plant (WWTP) effluents (e.g., consumer product ingredients). The effects of municipal wastewaters occurring in high population density (>500 persons per square mile, urban) and low population density (<500 persons per square mile, rural) environments were determined via analysis of biological, habitat, and water chemistry data collected both immediately upstream and downstream of 221 WWTPs in Ohio, USA. Several biological and chemistry indicators demonstrated poorer water quality in urban areas compared to rural areas. After considering the effect of river size, adverse effects downstream of WWTPs for both fish and macroinvertebrate communities were clearly identified for only urban areas. These data indicate that WWTP potency may be greater in urban areas compared to rural areas.

APPLICATION OF A WATERSHED MODEL TO EVALUATE MANAGEMENT EFFECTS ON POINT AND NONPOINT SOURCE POLLUTION

A Total Maximum Daily Load (TMDL) program has been initiated in the North Bosque River Watershed in Texas, USA, where point and nonpoint sources of pollution are of a concern. The Soil and Water Assessment Tool (SWAT), which had been validated for flow and sediment and nutrient transport, was applied to quantify the effects of Best Management Practices (BMPs) related to dairy manure management and municipal wastewater treatment plant effluent. Results are presented for the period from 1960 through 1998 for three sites along the North Bosque River. Results are presented as annual time–weighted concentrations (average of the daily load divided by daily flow over a year) and annual flow–weighted concentrations (total cumulative load divided by total cumulative flow over a year). The wastewater treatment plant BMPs resulted in greater improvement in time–weighted instream soluble phosphorus concentrations than dairy BMPs. On the other hand, dairy BMPs made greater differences in flow–weighted concentrations. This study showed that SWAT could be a useful tool for studying the effects of alternative management scenarios for pollution control from point and nonpoint sources in large watersheds.

Impact of a wastewater treatment plant on Cryptosporidium oocysts and Giardia cysts occurring in a surface water

The aim of this study was to assess the impact of a municipal wastewater treatment plant (MWTP) on the occurrence of Cryptosporidium oocysts and Giardia cysts in the receiving water. All MWTP effluent samples were Giardia and Cryptosporidium contaminated, although low mean values were found for both parasites (0.21±0.06 oocysts/L; 1.39±0.51 cysts/L). Otherwise, in the raw sewage a greater concentration was detected (4.5±0.3 oocysts/L; 53.6±6.8 cysts/L). The major occurrence of Giardia over Cryptosporidium, both in the influent and in the effluent of the MWTP, is probably related to the human sewage contribution to the wastewater. Data on protozoa contamination of the receiving water body demonstrated similar concentrations in the samples collected before (0.21±0.07 oocysts/L; 1.31±0.38 cysts/L) and after (0.17±0.09 oocysts/L and 1.01±1.05 cysts/L) the plant effluent discharge. The results of this study suggest that the MWTP has no impact related to Giardia and Cryptosporidium river water contamination, and underline the need for investigation into the effectiveness of these protozoa removal by less technologically advanced MWTPs which are the most widespread and could probably show a lower ability to reduce protozoa.

A study of selected pathogens in municipal wastewater treatment plant effluents

Wastewater reuse for irrigation increases the prevalence of health infections. Sixteen of the municipal wastewater treatment plants in Jordan, operated directly by the Government of Jordan, and others operated by the private sector are represented in this study which lasted for four years. Samples were collected from the effluents of these plants and were analysed for their content of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total fecal coliform count (TFCC), and parasites (protozoa and helminthes). The study concluded that the effluents of these plants are classified as moderate in strength in terms of BOD, COD, and TSS. It was also concluded based on the BOD, COD, TFCC and TSS results that the effluents of the treatment plants included in the study can be reused for irrigation purposes ranging from unrestricted irrigation to irrigation for animal feed. The results of TFCC indicated that the treated effluents of the treatment plants can be reused for irrigation for different purposes ranging from cooked vegetables to trees and pastures, and for dams and reservoirs. Results of the parasites content indicated that these effluents contain serious levels of parasites and cannot be reused to irrigate raw eaten vegetables. The study also provided recommendations to improve the performance of the treatment plants in terms of parasites removal.

Use of fly ash in reducing toxicity of and heavy metals in wastewater effluent

Fly ash is one of the most abundant waste materials; its major components make it a potential agent for the adsorption of heavy metal contaminants in water and wastewaters. The objective of this study was to measure the changes in toxicity of and heavy metals in a municipal (Salisbury, MD) wastewater treatment plant (SWTP) effluent on treatment with fly ash. The effluent from SWTP after treatment with fly ash for 4 h showed a significant reduction in toxicity, Cu and Pb, and PO 4 3− and NO 3 − contents. Toxicity of the effluent was measured using the marine luminescent microorganisms— Vibrio fischeri (‘Microtox’ test). Heavy metals (Cu, Pb and Zn) were measured using Atomic Absorption Spectrophotometry. Fly ash removed Cu and Pb from the effluent (through adsorption), and the removal of these toxic heavy metals resulted in the reduction of toxicity.

Flocculation in presence of organic macromolecules of natural water and secondary effluents

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand.

Flocculation in presence of organic macromolecules of natural water and secondary effluents

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand.

Ecotoxicological and chemical characterization of municipal wastewater treatment plant effluents

The toxicity and the chemical quality of three municipal wastewater effluents have been studied. Acute and sub-chronic bioassays were carried out. We also measured the induction of the hepatic ethoxy resorufin-O-deethylase enzymatic activity (EROD) of fish exposed to the effluents. Chemical analysis allowed to identify the most frequent substances detected in the effluents. From chemical data and results of bioassays we conclude that ammonia concentration explains a part of the lethal toxicity. But chronic toxicity tests carried out with whole effluents or extracted chemical fractions showed that organic pollutants detected in the effluents could also cause long-term effect. All the tested effluents induced fish EROD activity. The instream invertebrates monitoring confirmed the municipal wastewater treatment plant impact on the receiving water.

Ecotoxicological and chemical characterization of municipal wastewater treatment plant effluents

The toxicity and the chemical quality of three municipal wastewater effluents have been studied. Acute and sub-chronic bioassays were carried out. We also measured the induction of the hepatic ethoxy resorufm-O deethylase enzymatic activity (EROD) of fish exposed to the effluents. Chemical analysis allowed to identify the most frequent substances detected in the effluents. From chemical data and results of bioassays we conclude that ammonia concentration explains a part of the lethal toxicity. But chronic toxicity tests carried out with whole effluents or extracted chemical fractions showed that organic pollutants detected in the effluents could also cause long-term effect. All the tested effluents induced fish EROD activity. The instream invertebrates monitoring confirmed the municipal wastewater treatment plant impact on the receiving water

Significance of indicator bacteria changes in an urban stream

An urban coastal stream, above tidal reach, and three municipal wastewater treatment plant effluents were analyzed for fecal coliforms, fecal streptococci and enterococci to determine the effect of dechlorination on those bacterial populations. Analyses were conducted during low and high flow periods from stormwater inflow. Improvement in bacterial water quality was found, principally due to municipality efforts to correct illicit connections and other sewerage system problems. Fecal coliform genera were identified and quantified. Regrowth of dechlorinated effluent bacteria was minimal.

Significance of indicator bacteria changes in an urban stream

An urban coastal stream, above tidal reach, and three municipal wastewater treatment plant effluents were analyzed for fecal coliforms, fecal streptococci and enterococci to determine the effect of dechlorination on those bacterial populations. Analyses were conducted during low and high flow periods from stormwater inflow. Improvement in bacterial water quality was found, principally due to municipality efforts to correct illicit connections and other sewerage system problems. Fecal coliform genera were identified and quantified. Regrowth of dechlorinated effluent bacteria was minimal.

Identification of Non-Biodegradable, Hydrophilic, Organic Substances in Industrial and Municipal Waste Water Treatment Plant-Effluents by Liquid Chromatography-Tandem Mass Spectrometry (LC/MS/MS)

Effluents of biological waste water treatment plants containing high concentrations of non-biodegradable substances measured as COD (chemical oxygen demand) were analyzed by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). GC/MS could detect any relevant compound because of involatility of these substances. LC/MS/MS was able to give molecular weight information without any separation bypassing analytical column. Daughter- and parent-ions formed by MS/MS gave structural information by fragmentation under CID-conditions (collisionally induced dissociation) even for UV-non-detectable chromophor missing substances. Metabolites and anthropogenic, non-biodegradable substances such as polyether, nonionic alkyl-and arylsurfactants and benzene-sulfonic acid could be detected and identified after C 18 column separation and without any prior separation, bypassing column. Analysis without any separation could be done within a few minutes up to an hour, column separation lasted 10 to 100 fold longer.