Toxicity of different industrial effluents in Taiwan: a comparison of the sensitivity of Daphnia similis and Microtox

Theoretical and experimental studies on photocatalytic removal of methylene blue (MetB) from aqueous solution using oyster shell synthesized CaO nanoparticles (CaONP-O)

The development of technologies for the removal of dye from aqueous solution is most desirable if the end product is relatively green (i.e., environmentally friendly). Photodegradation (as one of such technology) and photolysis (without the catalyst) was applied to investigate the role of sol-gel synthesized calcium oxide nanoparticle (using the oyster shell as the precursor). The results obtained gave substantial evidence that calcium oxide nanoparticles catalyzed the degradation of the methylene blue dye up to a maximum percentage of 98 % removal. Degradation efficiency displayed a strong dependency on time, initial dye concentration, catalyst load, pH, and ionic strength. Chi-square and sum of square error analysis indicated that the photodegradation kinetics fitted the Langmuir-Hinshelwood, first order, and pseudo first-order models best. The half-life of the dye was significantly reduced from hours to minutes due to photocatalysis. Quantum chemical calculations indicated that the degradation proceeded through adsorption, deformation/degradation, and desorption through the chloride end of the molecule linked to the calcium active center of the catalyst. Results from Fukui functions and molecular descriptors analysis confirmed the mechanism of photocatalysis.

Artisanal tannery wastewater: quantity and characteristics

Tannery wastewater is one of the most toxic waste generated in industries. In spite of this, there still remains a paucity of information on characteristics of wastewater generated from artisanal tanneries. This study, therefore, assessed the water consumption, wastewater generation rates, physicochemical and microbiological characteristics of wastewater produced from each process unit of an artisanal tannery in Ghana. The study revealed that the total amount of water use in the tannery ranged between 1171 and 2120L/day whilst the total volume of wastewater generated was within 820 and 1324L/day. Physicochemical characteristics of the different wastewater types generated at the tannery including chemical oxygen demand (13600-24333.30 mg/L), biochemical oxygen demand (1445.64-2803 mg/L), ammonia (3.20-21.38 mg/L), colour (950.35-53900.10PtCo), electrical conductivity (8170 - 10080 μS/cm), turbidity (450.24-1805NTU), suspended (1033.50-3216.40 mg/L) and dissolved (26166.50-4996.65 mg/L) solids exceeded the guidelines set by the Ghana Environmental Protection Agency. There were also high levels of chlorides, sodium, sulphates and calcium ions. The most dominant anion and cation in the wastewater were chlorides (715-20490.60 mg/L) and sodium ions (258-14056.45 mg/L) respectively. Heavy metals identified in the wastewater included zinc, aluminium, iron and chromium ions with the most dominant one being aluminium ions (0.58-78.18 mg/L). Whilst the E-coli was below detectable limit, the count of total coliforms ranged between 0 and 4.5 × 10⁴CFU/100mL. Five helminth egg species (Ascaris lumbricoides, hookworm, Trichuris trichiura, Strongyloides stercoralis, and Enterobius vermicularis) were identified with their numbers surpassing the safe limit set by the World Health Organisation for irrigation purposes. These results indicated that the indiscriminate discharge of the untreated wastewater on the bare soil as it is practised at the tannery has the potential to adversely affect public and environmental health. Appropriate treatment schemes are therefore, required to treat the wastewater to safe limits prior to discharge.

Effects of water produced by oil segment on aquatic organisms after treatment using advanced oxidative processes

The water produced (PW) by the petroleum industry is a potential contaminant to aquatic biota, due to its complex mixture that may contain polycyclic aromatic hydrocarbons (PAHs), organic chemical compounds, including benzene, toluene, ethylbenzene and xylene (BTEX), metals and other components that are known to be toxic. The aim of this investigation was to examine the acute toxicity produced by a PW sample in aquatic organisms Vibrio fischeri and Daphnia similis prior to and after 4 treatments using advanced oxidative processes such as photocatalysis, photoelectrocatalysis, ozonation and photoelectrocatalytic ozonation. Data demonstrated that exposure to PW was toxic to both organisms, as evidenced by reduced luminescence in bacterium Vibrio fischeri and induced immobility in Daphnia similis. After treatment of PW with 4 different techniques, the PW remained toxic for both tested organisms. However, photoelectrocatalysis was more efficient in decreasing toxicity attributed to PW sample. Therefore, data demonstrate the importance of treating PW for later disposal in the environment in order to mitigate ecotoxicological impacts. Further photoelectrocatalysis appeared to be a promising tool for treating PW samples prior to disposal and exposure of aquatic ecosystems.

Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment: A review

Vibrio fischeri bioluminescence inhibition bioassay (VFBIA) has been widely applied for the monitoring of toxicity on account of multiple advantages encompassing shorter test duration, sensitive, cost-effective and ease of operation. Moreover, this bioassay found to be equally applicable to all types of matrices (organic & inorganic compounds, metals, wastewater, river water, sewage sludge, landfill leachate, herbicides, treated wastewater etc.) for toxicity monitoring. This review highlights the apparent significance of Vibrio fischeri bioluminescence inhibition assay for ecotoxicological screening and evaluation of diverse chemical substances toxicity profile. The biochemical and genetic basis of the bioluminescence assay and its regulatory mechanism have been concisely discussed. The basic test protocol with ongoing improvements, widespread applications, typical advantages and probable limitations of the assay have been overviewed. The sensitivity of VFBIA and toxicity bioassays has also been compared.

The effect of the feeding pattern of complex industrial wastewater on activated sludge characteristics and the chemical and ecotoxicological effluent quality

Research has demonstrated that the feeding pattern of synthetic wastewater plays an important role in sludge characteristics during biological wastewater treatment. Although considerable research has been devoted to synthetic wastewater, less attention has been paid to industrial wastewater. In this research, three different feeding strategies were applied during the treatment of tank truck cleaning (TTC) water. This industry produces highly variable wastewaters that are often loaded with hazardous chemicals, which makes them challenging to treat with activated sludge (AS). In this study, it is shown that the feeding pattern has a significant influence on the settling characteristics. Pulse feeding resulted in AS with a sludge volume index (SVI) of 68 ± 15 mL gMLSS^-1. Slowly and continuously fed AS had to contend with unstable SVI values that fluctuated between 100 and 600 mL gMLSS^-1. These fluctuations were clearly caused by the feeding solution. The obtained settling characteristics are being supported by the microscopic analysis, which revealed a clear floc structure for the pulse fed AS. Ecotoxicological effluent assessment with bacteria, Crustacea and algae identified algae as the most sensitive organism for all effluents from all different reactors. Variable algae growth inhibitions were measured between the different reactors. The chemical and ecotoxicological effluent quality was comparable between the reactors.

Toxicity assessment using different bioassays and microbial biosensors

Toxicity assessment of water streams, wastewater, and contaminated sediments, is a very important part of environmental pollution monitoring. Evaluation of biological effects using a rapid, sensitive and cost effective method can indicate specific information on ecotoxicity assessment. Recently, different biological assays for toxicity assessment based on higher and lower organisms such as fish, invertebrates, plants and algal cells, and microbial bioassays have been used. This review focuses on microbial biosensors as an analytical device for environmental, food, and biomedical applications. Different techniques which are commonly used in microbial biosensing include amperometry, potentiometry, conductometry, voltammetry, microbial fuel cells, fluorescence, bioluminescence, and colorimetry. Examples of the use of different microbial biosensors in assessing a variety of environments are summarized.

Assessment of the toxicity of wastewater from the metalworking industry treated using a conventional physico-chemical process

This article presents results from a toxicity reduction evaluation program intended to describe wastewater from the metalworking industry that was treated using a conventional physico-chemical process. The toxicity of the wastewater for the microcrustacean Daphnia magna was predominantly expressive. Alkaline cyanide wastewater generated from electroplating accounted for the largest number of samples with expressive toxicity. When the raw wastewater concentrations in the batches were repeated, inexpressive toxicity variations were observed more frequently among the coagulated-flocculated samples. At the coagulation-flocculation step, 22.2 % of the treatments had reduced acute toxicity, 30.6 % showed increased toxicity, and 47.2 % remained unchanged. The conductivity and total dissolved solids contents of the wastewater indicated the presence of salts with charges that were inappropriate for the survival of daphnid. The wastewaters treated by neutralization and coagulation-flocculation had average metallic compound contents that were greater than the reference toxic concentrations reported in other studies, suggesting that metals likely contributed to the toxic effects of the wastewater on freshwater microcrustaceans. Thus, alternative coagulants and flocculants should be assessed, and feasible doses should be determined to improve wastewater treatment. In addition, advanced treatment processes should be assessed for their abilities to remove dissolved toxic salts and ions.

Semi-continuous detection of toxic hexavalent chromium using a sulfur-oxidizing bacteria biosensor

Toxicity testing is becoming a useful tool for environmental risk assessment. A biosensor based on the metabolic properties of sulfur-oxidizing bacteria (SOB) has been applied for the detection of toxic chemicals in water. The methodology exploits the ability of SOB to oxidize elemental sulfur to sulfuric acid under aerobic conditions. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. Five hours after Cr(6+) was added to the SOB biosensor operated in semi-continuous mode (1 min rapid feeding and 29 min batch reaction), a decrease in effluent EC and an increase in pH (from 2-3 to 6) were detected due to Cr(6+) toxicity to SOB. The SOB biosensor is simple; it can detect toxic levels of Cr(6+) on the order of minutes to hours, a useful time scale for early warning detection systems designed to protect the environment from further degradation.

Assessing acute toxicity of effluent from a textile industry and nearby river waters using sulfur-oxidizing bacteria in continuous mode

Bioassays are becoming an important tool for assessing the toxicity of complex mixtures of substances in aquatic environments in which Daphnia magna is routinely used as a test organism. Bioassays outweigh physicochemical analyses and are valuable in the decision-making process pertaining to the final discharge of effluents from wastewater treatment plants as they measure the total effect of the discharge which is ecologically relevant. In this study, the aquatic toxicity of a textile plant effluent and river water downstream from the plant were evaluated with sulfur-oxidizing bacterial biosensors in continuous mode. Collected samples were analysed for different physicochemical parameters and 1,4-dioxane was detected in the effluent. The effluent contained a relatively high chemical oxygen demand of 60 mg L(-1), which exceeded the limit set by the Korean government for industrial effluent discharges. Results showed that both the effluent and river waters were toxic to sulfur-oxidizing bacteria. These results show the importance of incorporating bioassays to detect toxicity in wastewater effluents for the sustainable management of water resources.

The azo dye Disperse Orange 1 induces DNA damage and cytotoxic effects but does not cause ecotoxic effects in Daphnia similis and Vibrio fischeri

Azo dyes constitute the largest group of colorants used in industry and can pass through municipal waste water plants nearly unchanged due to their resistance to aerobic treatment, which potentially exposes humans and local biota to adverse effects. Unfortunately, little is known about their environmental fate. Under anaerobic conditions, some azo dyes are cleaved by microorganisms forming potentially carcinogenic aromatic amines. In the present study, the azo dye Disperse Orange 1, widely used in textile dyeing, was tested using the comet, Salmonella/microsome mutagenicity, cell viability, Daphnia similis and Microtox(®) assays. The human hepatoma cell line (HepG2) was used in the comet assay and for cell viability. In the mutagenicity assay, Salmonella typhimurium strains with different levels of nitroreductase and o-acetyltransferase were used. The dye showed genotoxic effects with respect to HepG2 cells at concentrations of 0.2, 0.4, 1.0, 2.0 and 4.0μg/mL. In the mutagenicity assay, greater responses were obtained with the strains TA98 and YG1041, suggesting that this compound mainly induces frameshift mutations. Moreover, the mutagenicity was greatly enhanced with the strains overproducing nitroreductase and o-acetyltransferase, showing the importance of these enzymes in the mutagenicity of this dye. In addition, the compound induced apoptosis after 72h in contact with the HepG2 cells. No toxic effects were observed for either D. similis or Vibrio fischeri.

Toxicity assessment of dye containing industrial effluents by acute toxicity test using Daphnia magna

Toxicity of dye containing effluent of tannery, textile, dyes and pulp-paper industries was evaluated in an acute toxicity test using Daphnia magna. The 48-hour EC(50) values were 4.33% and 19.5% for tannery effluents (Tn1 and Tn2). Textile effluents (Tx1-Tx7) had 48-hour EC(50) values; >100%, >100%, 62.9%, 63.0%, 40.3%, >100% and >100%, respectively. Dye industries (D1-D7) had 48-hour EC(50) values; 14.1%, 15.5%, 24.5%, 29.7%, 23.2%, >100% and >100%, respectively. Similarly pulp-paper effluents (P1-P5) showed acute toxicity as 100%, 77.87%, 46.44%, 69.55% and 82.84%, respectively. These results showed linear relationship with high degree of confidence (r(2) ≥ 0.84-0.99) between immobility and test concentrations. Toxicity classification criteria showed that out of five effluents from pulp-paper mill, four were minor acutely toxic having 48-hour EC(50) value in between >46%-100%. Out of seven textile effluents, four were not acutely toxic (48-hour EC(50) value >100%) and three were minor acutely toxic (48-hour EC( 50) value in the range of 40.3%-63.0%). Similarly, out of seven dye industrial effluents, two were not acutely toxic and five minor acutely toxic. One of the two tanneries was moderately acutely toxic and another one was minor acutely toxic. Classification based on toxic unit revealed that four out of five pulp-paper effluent, three out of seven textile effluents, five out of seven dye effluents and both the tannery effluents were toxic. Overall, 66.67% effluents were found toxic and 33.33% as non-toxic. In general, tannery and dyes effluents showed more toxicity than textile and paper mill effluents.

Acute toxicity assessment of textile dyes and textile and dye industrial effluents using Daphnia magna bioassay

Aquatic toxicity of textile dyes and textile and dye industrial effluents were evaluated in an acute toxicity study using Daphnia magna as an aquatic experimental animal model. The 48-h EC50 value for the azo dyes, Remazol Parrot Green was 55.32 mg/L and for Remazol Golden Yellow was 46.84 mg/L. Whereas 48-h EC50 values for three dye industrial effluents (D1, D2, and D3) were 14.12%, 15.52%, and 29.69%, respectively. Similarly, EC50 value for three textile mill effluents (T1, T2, and T3) were >100%, 62.97%, and 63.04%, respectively. These results also showed linear relationship with high degree of confidence ( r2 = >0.84 to >0.99) between immobility and test concentrations. The ratio of 24 to 48-h EC50 remains to be in between 1.1 and 1.2. The general criteria of toxicity classification showed that both dyes were minor acutely toxic having 48-h EC50 in between 10 and 100 mg/L. Of the six textile and dye industrial effluents tested, one was not acutely toxic (48-h EC50 > 100%) and five were minor acutely toxic (48-h EC50 > 14.12–29.69%). The toxicity classification of effluent based on toxic unit (TU) showed that of the six effluents tested five were found toxic (TU = >1) and one was non-toxic (TU = <1). Thus, dye effluents showed highest toxicity and textile effluents lowest toxicity. The study also suggested that the assay with D. magna was an excellent method for evaluation of aquatic toxicity of dyes and dyes containing industrial effluents.

Toxicity assessment of a complex industrial wastewater using aquatic and terrestrial bioassays Daphnia pulex and Lactuca sativa

Aquatic and terrestrial bioassays were used to assess toxicity at several stages in an industrial wastewater treatment plant that processes 400 L/s from a complex influent formed by wastewater from 135 industries. Daphnia pulex and Lactuca sativa were used to assess and compare toxicity between the influent wastewater and effluent wastewater from an activated sludge process, and compare their relationship with physicochemical parameters of Biological Oxygen Demand (BOD); Chemical Oxygen Demand (COD); Total Suspended Solids (TSS); total Nitrogen (N (N-total)), and ammonia Nitrogen (N (N - NH3)). Samples from the primary clarifiers (PC), mix liquor stage (ML) and secondary clarifiers (SC) were processed using physicochemical and bioassay test. Toxicity results with Daphnia pulex showed decreased mean values of acute Toxic Units (a.T.U.) between PC (2.1 a.T.U.) and SC (1,25 a.T.U.). Lactuca sativa showed high values of toxicity between PC and SC (3.37 and 3.32 a.T.U. respectively). Some samples exhibited higher toxicity values at the effluent stage (SC) than the influent stage (PC). The highest correlations of physicochemical properties with toxicity were obtained with COD and nitrogen compounds in effluent samples (SC), but not with influent samples (PC).

Biological and electrochemical treatment of used metalworking fluids: a toxicity-reduction evaluation

The aim of this study was to evaluate and compare the toxicity of spent metalworking fluids (MWFs) and two different effluents obtained by biologic and electrochemical treatment of spent MWFs toward aquatic organisms of different trophic levels. The obtained toxicity data was used to calculate safe concentrations of both effluents. The spent MWFs without treatment showed the highest toxicity among the tested samples and should be classified as "extremely toxic" (toward invertebrates) or "very toxic" (toward other test organisms). Both methods applied for MWFs treatment resulted in a significant decrease in toxicity of the treated MWFs, but the obtained effluents had still to be regarded as "toxic". The ranges of the values of acute toxic units for both effluents were significantly narrower than for the untreated spent MWFs. The values of the safe concentrations of the spent MWFs, the biologic effluent, and the water phase resulting from electrochemical emulsion breaking were equal to 0.013%, l.8%, and 1.3%, respectively, corresponding to chemical oxygen demand concentrations of 1.8%, 32, and 34 mg O(2)*L(-1). These values are far lower than the discharging limit of 125 mg O(2)*L(-1) for industrial effluents, according to the relevant Polish regulations. It is therefore recommended to include toxicity bioassay parameters into guidelines for wastewater discharges to surface waters because the existing chemical and physical parameters are not sufficient to describe the environmental impact of industrial wastewater. Toxicity bioassays can be a promising tool for evaluating the efficacy of unit operations in industrial wastewater treatment (toxicity reduction evaluation) as well as identification of toxic substances in effluents (toxicity identification evaluation).

Cr(VI) reduction into Cr(III) as a mechanism to explain the low sensitivity of Vibrio fischeri bioassay to detect chromium pollution

Vibrio fischeri bacteria, used as a biological target in either acute or chronic toxicity tests, display a low sensitivity to Cr(VI). This phenomenon could be due to the capacity of these bacteria to reduce Cr(VI) into Cr(III). This reducing capacity was found to depend on culture medium composition, pH value, incubation time and the presence of a carbon source. It also depends on the nature of the carbon source, glucose being more efficient than glycerol. This is probably related to differences in bacterial metabolism when given either glucose or glycerol. The thermostable Cr(VI)-reducing activity found in the supernatants of V. fischeri cultures grown on glucose suggests that, under these conditions, the bacteria release non-proteic reducing substances which have not been identified yet.