Biological treatment of the effluent from a bleached kraft pulp mill using basidiomycete and zygomycete fungi

Three white-rot fungi (Pleurotus sajor caju, Trametes versicolor and Phanerochaete chrysosporium) and one soft-rot fungi (Rhizopus oryzae) species confirmed their potential for future applications in the biological treatment of effluents derived from the secondary treatment of a bleached kraft pulp mill processing Eucalyptus globulus. Among the four species P. sajor caju and R. oryzae were the most effective in the biodegradation of organic compounds present in the effluent, being responsible for the reduction of relative absorbance (25-46% at 250 nm and 72-74% at 465 nm) and of chemical oxygen demand levels (74 to 81%) after 10 days of incubation. Laccase (Lac), lignin (Lip) and manganese peroxidases (MnP) expression varied among fungal species, where Lac and LiP activities were correlated with the degradation of organic compounds in the effluent treated with P. sajor caju. The first two axes of a principal component analysis explained 88.9% of the total variation among sub-samples treated with the four fungus species, after different incubation periods. All the variables measured contributed positively to the first component except for the MnP enzyme activity which was the only variable contributing negatively to the first component. Absorbances at 465 nm, LiP and Lac enzyme activities were the variables with more weight on the second component. P. sajor caju revealed to be the only species able to perform the biological treatment without promoting an increment in the toxicity of the effluent to the Vibrio fischeri, as it was assessed by the Microtox® assay. The opposite was recorded for the treatments with the other three species of fungus. EC_50-5 min values ranging between 28 and 57% (effluent concentrations) were recorded even after 10 to 13 days of treatment with P. chrysosporium, R. oryzae or with T. versicolor.     

An evaluation of the potential toxicity of treated bleached kraft mill effluent to striped bass (Morone saxatilis walbaum) larvae exposed through metamorphosis to the juvenile stage

Twenty-day-old striped bass (Morone saxatilis) larvae were exposed to a range of treated bleached kraft mill effluent (BKME) concentrations from 0 to 20% effluent by volume (v/v) under continuous flow test conditins. The experimental test concentrations in the 2–20% BKME test aquaria had a BOD₅ which ranged from < 1 to 5 mg l⁻¹, TSS 12–17 mg l⁻¹, and true color 35–416 mg l⁻¹. Bleached kraft mill effluent did not kill larvae exposed to it for 20 days through metamorphosis to the juvenile stage. The BKME did not alter growth in length, weight or condition factor in larvae over the 20-day exposure period as determined by multiple regression analysis. A linear regression analysis on the dry weight data at Day 20 only, however, indicated a trend of decreasing weight with increasing BKME concentration. Effluent-exposed larvae also developed normally during the 20-day study. All individuals examined completed the transformation from postlarvae to juveniles by the age of 40 days.     

Phenolic removal in a model olive oil mill wastewater using Pleurotus ostreatus in bioreactor cultures and biological evaluation of the process

Pleurotus ostreatus grown in bioreactor batch cultures in a model phenolic wastewater (diluted and sterilized olive oil mill wastewater-OMW), caused significant phenolic removal. Laccase, the sole ligninolytic enzyme detected in the growth environment, was produced during primary metabolic growth. The bioprocess was simulated with the aid of a mathematical model and the parameters of growth were determined. When the fungal biomass was increased in the reactor (during repeated batch experiments) the rate of reducing sugars consumption progressively increased, but a phenolic fraction seemed of being strongly resistant to oxidation. The toxicity of OMW against the seeds of Lepidium sativum and the marine Branchiopoda Artemia sp. was significantly decreased after biotreatment. On the contrary, the toxicity against the freshwater Branchiopoda Daphnia magna was not affected by the treatment, whereas on the soil and freshwater sediments Ostracoda Heterocypris incongruens was slightly decreased. Both treated and untreated OMWs, used as water for irrigation of lettuce and tomato plants, did not significantly affect the uptake of several nutrients by the cultivated plants, but resulted in a decrease in the plant yields, which was minimized when high OMW dilutions were used. As a conclusion, P. ostreatus is able to reduce phenolic content and toxicity of sterilized OMW, in bioreactor cultures. However, high OMW dilutions should be used, and/or additional treatment should be applied before use of the OMW in the environment, e.g. as water for irrigation. Further research should be done in order to transfer this technology under industrial conditions (e.g. by using unsterilized OMW).     

In situ biomonitoring of freshwater quality using the New Zealand mudsnail Potamopyrgus antipodarum (Gray) exposed to waste water treatment plant (WWTP) effluent discharges

Mollusk species have been shown to be sensitive to various endocrine disrupting compounds (EDC) at environmentally relevant concentrations. Waste water treatment plant (WWTP) effluents are a major source of potential or known EDC in the aquatic environment. The aim of this study was to develop an in situ exposure method using the New Zealand mudsnail Potamopyrgus antipodarum (Molluska, Hydrobiidea) to assess the impact of water quality on the life traits of this species, by focusing on its reproduction. The impact of three WWTP discharges on three different receiving rivers was studied. The effects of WWTP effluent on adult survival, weight, reproduction and vertebrate-like sex-steroid levels in snails were monitored for three to four weeks. Although the physicochemical and hydrological parameters varied greatly between the rivers, the caging experiments allowed us to detect significant impairment of the life traits of snails when exposed downstream of the WWTPs discharge. While adult survival was not affected by exposure, reproduction was significantly impacted downstream from the WWTP effluent discharges (60-70% decrease of embryos without shells after three to four weeks exposure) independently of the river. Modulations of steroid levels proved to be an informative parameter with an increase of testosterone downstream of the discharges, and increases and decreases of 17β-estradiol levels according to site. The endpoints used proved to be an adapted method for field exposures and allowed the discrimination between upstream and downstream sites.     

Effects of lignin and chlorolignin in pulp mill effluents on the binding and bioavailability of hydrophobic organic pollutants

The partition coefficients (K_p) of benzo(a)pyrene (BaP), 3,3′,4,4′-tetrachlorobiphenyl (TCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to dissolved kraft lignin (Indulin AT), chlorolignin isolated from a bleached kraft mill effluent (BKME) and dissolved organic matter (DOM) in a lake receiving BKME were measured by equilibrium dialysis. The K_p values of kraft lignin were 28.2 × 10⁵, 6.5 × 10⁵ and 15.9 × 10⁵ and those of chlorolignin were 8.3 × 10⁵, 2.9 × 10⁵ and 2.2 × 10⁵ for BaP, TCB and TCDD, respectively. In addition, DOM in a series of lake water samples collected from the southern part of Lake Saimaa, SE Finland, receiving BKME revealed higher binding capacities to all of the three model compounds than natural DOM in water upstream from the pulp mill. An important phenomenon related to the environmental transport and fate of xenobiotics was almost the full reversibility of the binding between chlorolignin and model compounds. The obtained K_p values of chlorolignin after a 4 day dissociation period were 12.6 × 10⁵ and 4.6 × 10⁵ for BaP and TCDD, respectively.In short-term (24 h) accumulation experiments with Daphnia magna the effects of kraft lignin and chlorolignin on the bioavailability of three model compounds was very clear. The bioconcentration factors of the xenobiotics in the chlorolignin containing water (DOC = 10 mg C/l) were 20–30 and 25–35% of those organic-free control and upstream reference waters (DOC = 7.2 mg C/l), respectively. The effect of chlorolignin of BKME on the bioavailability of model compounds was also seen in the lake water series of Lake Saimaa.     

Effect of biological wastewater treatment on the molecular weight distribution of soluble organic compounds and on the reduction of BOD, COD and P in pulp and paper mill effluent

Pulp and paper mill wastewater was characterizated, before (influent) and after (effluent) biological wastewater treatment based on an activated sludge process, by microfiltration (8, 3, 0.45 and 0.22mum) and ultrafiltration (100, 50, 30 and 3kDa) of the wastewater samples into different size fractions. Various parameters were measured on each fraction: molecular weight distribution (MWD) using high performance size exclusion chromatography (HPSEC), total organic carbon (TOC), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (Tot-P), phosphate phosphorus (PO(4)-P), electrical conductivity, pH, turbidity, charge quantity and zeta potential. The MWD, TOC and COD(Cr) results indicated that the majority of the material present in both the influent and effluent was in the medium molecular weight (MW) range (i.e. MW<10kDa) with three main MW sub-fractions. There were no significant differences in the range of the MWD between the influent and effluent samples. The magnitude of the MWD in the effluent was about one half that in the influent, the greatest reduction being in the 6kDa fraction. The 3kDa fractions of both the influent and effluent showed a considerable increase in BOD(7), probably due to the removal of compounds harmful to bacteria in 3kDa ultrafiltration. Influent turbidity decreased considerably in microfiltration (8-0.22mum). As the turbidity was removed by 0.22mum filtration, the anionic charge quantity started to decrease. Particles in the influent and effluent contained 19-29% and 14-20% of the total phosphorus, respectively. The major phosphorus fraction was in the form of soluble phosphate.     

A seasonal study of the mecA gene and Staphylococcus aureus including methicillin-resistant S. aureus in a municipal wastewater treatment plant

The spread of methicillin-resistant Staphylococcus aureus (MRSA), in which the mecA gene mediates resistance, threatens the treatment of staphylococcal diseases. The aims were to determine the effect of wastewater treatment processes on mecA gene concentrations, and the prevalence of S. aureus and MRSA over time. To achieve this a municipal wastewater treatment plant was investigated for the mecA gene, S. aureus and MRSA, using real-time PCR assays. Water samples were collected monthly for one year, at eight sites in the plant, reflecting different aspects of the treatment process. The mecA gene and S. aureus could be detected throughout the year at all sampling sites. MRSA could also be detected, but mainly in the early treatment steps. The presence of MRSA was verified through cultivation from inlet water. The concentration of the mecA gene varied between months and sampling sites, but no obvious seasonal variation could be determined. The wastewater treatment process reduced the mecA gene concentration in most months. Taken together our results show that the mecA gene, S. aureus and MRSA occur over the year at all sites investigated.     

An investigation into the occurrence of sewage fungus in rivers containing papermill effluents—IV. Growth in experimental channels dosed with effluents and pure compounds

Wastewaters from the manufacture of pulp and paper have given rise to problems of excessive microbial growth in rivers over a number of years. This paper is the first in a series of four articles describing research undertaken by PIRA at four U.K. paper/board mills (one integrated with pulp production) over the period 1978–1980. This first paper briefly reviews the published literature on sewage fungus growth from pulp and paper mill discharges up to 1978, but mainly describes previously unpublished work undertaken by PIRA over the period 1965–1975. This introductory paper thus provides a state-of-the-art review of methods to control sewage fungus growth from pulp and paper mill effluents prior to commencement of the research described in the following three articles.     

Occurrence and diversity of Arcobacter spp. along the Llobregat River catchment, at sewage effluents and in a drinking water treatment plant

The presence of Arcobacter species in faecally contaminated environmental waters has previously been studied. However, the ability to eliminate Arcobacter during the water treatment processes that produce drinking water has been little studied. We have investigated the prevalence and diversity of Arcobacter spp. throughout the year at 12 sampling points in the Llobregat River catchment (Catalonia, Spain) including 3 sites at a drinking water treatment plant. Positive samples for Arcobacter spp., came predominantly from the most faecally polluted sites. Recovery rates from all sites were greater in the spring (91.7%) and summer (83.3%) than in autumn and winter (75.0% in both cases), but this trend was not statistically evaluated due to the limited number of samples. Among the 339 colonies analyzed, the most prevalent species by multiplex PCR and 16S rDNA restriction fragment length polymorphism were Arcobacter butzleri (80.2%), followed by Arcobacter cryaerophilus (19.4%) and Arcobacter skirrowii (0.3%). Isolates showed a high genotype diversity as determined by the enterobacterial repetitive intergenic consensus PCR. In fact, 91.2% (309/339) of the colonies had different genotypes, i.e. 248 of them among the 275 isolates of A. butzleri and 60 among the 63 isolates of A. cryaerophilus and 1 genotype of A. skirrowii. Arcobacter was never detected or isolated from finished drinking water, demonstrating that water treatment is effective in removing Arcobacter species.