Degradation of polyethoxylated nonylphenols in a sewage treatment plant. Quantitative analysis by isotopic dilution-HRGC/MS

Polyethoxylated alkylphenols (APnEO, where n is the number of ethylene oxide molecules), are non-ionic surfactants widely used for domestic and industrial purposes. Most of APnEO are polyethoxylated nonylphenols (NPnEO). NPnEO are widespread environmental pollutants with relatively low toxicity for mammals and higher toxicity for aquatic organisms. In addition, they have been described as endocrine disrupters in recent publications. One of the main problems related to these surfactants is their uncomplete degradation, even in the most effective sewage treatment plants. Usually, the final products, more toxic and resistant to biological degradation than NPnEO, are nonylphenol (NP), monoethoxylated nonylphenol (NP1EO), diethoxylated nonylphenol (NP2EO), nonylphenoxy acetic acid (NP1EC), and nonylphenoxyethoxy acetic acid (NP2EC). In this paper, the degradation of NPnEO was studied in the different processes of a sewage treatment plant. For this purpose, NP, NP1EO and NP2EO were analysed in composite samples collected at different points along the plant (influent, pre-treatment effluent, primary effluent, plant effluent). Analyses were carried out by isotopic dilution-HRGC/MS, using available labelled nonylphenols (13C6-NP, 13C6-NP1EO, 13C6-NP2EO) as internal standards. Extraction of NPnEO from aqueous samples, previous to analysis, was performed by the Likens-Nickerson method (simultaneous steam distillation/solvent extraction, SDE).     

Occurrence and fate of endocrine disrupters in Greek sewage treatment plants

The occurrence of five endocrine-disrupting compounds (EDCs), namely 4-n-nonylphenol (4-n-NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), triclosan (TCS) and bisphenol A (BPA), was assessed in the raw, treated wastewater and sewage sludge of eight sewage treatment plants (STPs) in Greece. The analytes were extracted by solid-phase extraction (dissolved phase) or sonication (solid phase). Qualitative and quantitative analyses were performed by gas chromatography-mass spectrometry (GC-MS). The average concentrations in the raw and treated wastewater ranged from 0.23 (4-n-NP) to 5.76microgL(-1) (NP1EO) and from 0.15 (BPA) to 1.84microgL(-1) (NP2EO), respectively. A great part of the detected EDCs was sorbed on suspended solids. In sewage sludge, the average concentrations ranged between 0.17 (4-n-NP) and 12.3microgg(-1)dw (NP1EO). Analysis of daily mass flows in STP of Athens showed that, with the exception of 4-n-NP, all other EDCs were significantly removed (>85%) during wastewater treatment. Regarding the fate of these compounds, a significant part ranging from 45% (for TCS) to more than 70% (for NP1EO, NP2EO and BPA) was transformed by abiotic or biotic mechanisms, while the rest was accumulated in sewage sludge or disposed to the environment via the effluents. Calculation of risk quotients showed the existence of possible threat due to the presence of certain EDCs in treated wastewater and sludge.     

Occurrence and risk assessment of nonylphenol and nonylphenol ethoxylates in sewage sludge from different conventional treatment processes

In the present work, the concentrations of the organic pollutants nonylphenol (NP) and nonylphenol mono- and diethoxylates (NP1EO and NP2EO, respectively) in primary, secondary, mixed, aerobically-digested, anaerobically-digested, dehydrated, compost and lagoon sludge samples from different sludge treatments have been evaluated. Toxicological risk assessment of these compounds in sludge and sludge-amended soil has also been reported. NP, NP1EO and NP2EO were monitored in sludge samples obtained from treatment plants located in Andalusia (south of Spain) based on anaerobic treatments (11 anaerobic-digestion wastewater treatment plants and 3 anaerobic wastewater stabilization ponds) or on aerobic treatments (3 aerobic-digestion wastewater treatment plants, 1 dehydration treatment plant and 2 composting plants). The sum of NP, NP1EO and NP2EO (NPE) concentrations has been evaluated in relation to the limit value of 50 mg/kg set by the European Union Sludge Directive draft published in April 2000 (Working Document on Sludge). In most of the samples, NP was present at higher concentration levels (mean value 88.0 mg/kg dm) than NP1EO (mean value 33.8 mg/kg dm) and NP2EO (mean value 14.0 mg/kg dm). The most contaminated samples were compost, anaerobically-digested sludge, lagoon sludge and aerobically-digested sludge samples, which contained NPE concentrations in the ranges 44-962 mg/kg dm, 8-669 mg/kg dm, 27-319 mg/kg dm and 61-282 mg/kg dm, respectively. Risk quotients, expressed as the ratios between environmental concentrations and the predicted no-effect concentrations, were higher than 1 for NP, NP1EO and NP2EO in the 99%, 92% and 36% of the studied samples, respectively; and higher than 1 in the 86%, 6% and 2%, respectively, after sludge application to soil, leading to a significant ecotoxicological risk mainly due to the presence of NP.     

Occurrence of selected surfactants in untreated and treated sewage

Several surfactants were monitored in treated and untreated sewage in nine municipal wastewater treatment plants (WWTPs) in western Austria. The nine sampled WWTPs cover a wide variety referring to size and applied treatment technology. The investigation focused on linear alkylbenzene sulphonate (LAS), quaternary ammonia compounds (QAC), nonylphenol (NP), octylphenol (OP), nonylphenolmono- (NP(1)EO) and -diethoxylates (NP(2)EO). Whereas LAS, NP, OP and NP(1,2)EO were analysed separately in the liquid phase and in the solid phase, the QACs were measured in the total sample. Total influent concentrations of LAS varied between 2.4 mg l(-1) up to 6.7 mg l(-1) whereas total effluent concentrations were in the lower microg l(-1) range (11-50 microg l(-1)). Whichever the type of treatment, a clear removal during treatment was observed. Solid liquid distribution coefficients K(d) were calculated for untreated sewage. The calculated K(d) values varied between 1300 and 3900 l kg(-1). OP was of minor importance with total influent concentrations below 1microg l(-1). NP and NP(1,2)EO were present in all analysed influents in concentrations between 1 and 35microg l(-1). Effluent concentrations were notably lower than the measured influent concentrations. K(d) values for NP varied between 500 and 6600 l kg(-1), for NP(1)EO between 800 and 2700 l kg(-1) and for NP(2)EO between 100 and 1800 l kg(-1). From the QACs several alkyl benzyl (BAC), dialkyl (DDAC) and trialkyl (ATAC) ammonium chlorides with varying alkyl chain lengths were analysed. Highest total concentrations in the influents to the WWTPs were observed for the BAC-C12 and the ATAC-C16 homologues. Effluent concentrations were notably lower compared to influent concentrations, indicating removal by adsorption and/or biodegradation. The influence of the removal by adsorption increased with increasing alkyl chain length.     

Bacterial community shifts in nonylphenol polyethoxylates-enriched activated sludge

A molecular approach was used to evaluate the effect of nonylphenol ethoxylate surfactants on the bacterial diversity in lab-scale activated sludge reactors. Separate bench-scale units were fed synthetic wastewater with and without addition of branched nonylphenol ethoxylates (NPnEO). The performance of the reactors, in terms of carbonaceous removal was largely unaffected by the presence of NP10EO in the feeding solution. However, addition of NP10EO exerted a pronounced shift in bacterial community composition. In situ hybridization analyzing larger phylogenetic groups of bacteria with ribosomal RNA-targeted oligonucleotide probes revealed the dominance of clusters composed of Betaproteobacteria, accounting for up to one-third of 4',6-diamidino-2-phenylindol-dihydrochloride (DAPI)-stained cells in NP10EO amended reactors and only 5% of DAPI-stained cells in the controls. These shifts in populations of larger phylogenetic groups were confirmed by dot-blot analysis of rRNA. Members of gamma subclass of Proteobacteria were present in low numbers in all activated sludge samples examined, suggesting that only bacteria affiliated with the beta subclass of Proteobacteria may have a specific role in NP10EO degradation.     

Treatment of raw domestic sewage in an UASB reactor

The treatment of raw domestic sewage at ambient temperatures in an upflow anaerobic sludge blanket (UASB) reactor with a volume of 120 l. and a height of 1.92 m was studied. The sewage had an average BOD₅ of 357 mg l⁻¹ and COD of 627 mg l⁻¹. Approximately 75% of the organic materials were in the suspended fraction. The sewage temperature ranged from 18 to 28°C during the experimental period. The reactor operated continuously for 9 months and assessed self-inoculation and raw domestic sewage purification. The unit was started without inoculum and ran during the entire experimental period with a hydraulic retention time of 4 h. During the experiment, a sludge bed build-up was observed. At the end of the experimental period, the predominance of spherical granular particles up to 6–8 mm in diameter was evident.

After a 4-month operation, it was observed that the inoculation/acclimatization steps had been concluded. Removal efficiencies of BOD₅ = 78%, COD = 74% and TSS = 72% were obtained. A typical gas production factor of 80 l kg⁻¹ COD added was observed and the CH₄ content of the biogas was 69%.     

Anaerobic treatment of domestic sewage with a rotating stationary fixed-film reactor

An anaerobic reactor was developed for on-site and small scale wastewater treatment applications. The up-flow fixed-film reactor was packed with two different types of circular media: stationary and rotating. Experimental results showed the reactor can treat primary settled domestic wastewaters efficiently, under different operating conditions. At 29°C the mixing action did not improve the organic matter removal efficiencies (65% COD removal was obtained with an organic load of 1.7 kg COD m⁻³ day⁻¹ and a 6 h space time). However, at 16°C the removal efficiency was greatly dependent on the mixing conditions: a gentle agitation (5 rpm) up-graded significantly the reactor operation, but no improvement was observed beyond 15 rpm. It appears that at low temperatures liquid biofilm mass transfer is the rate limiting step when treating sewage anaerobically. Gas production was rather limited [0.11 m³ (STP) kg⁻¹ COD removed] and calculations suggest that more than 50% of the total CH₄ produced is lost due to its dissolution in the effluent. Improved effluent quality, reduced sludge production (0.11 kg TSS kg⁻¹ COD supplied), low energy requirements and low maintenance needs make this reactor a good, compact alternative to conventional household wastewater treatment processes.     

Plant-scale phosphate removal experiments at the Balatonfüred sewage treatment plant

Operational parameters at the Balatonfüred sewage treatment plant and the technology of chemical phosphate removal on a plant-scale have been examined in a 3-week series of experiments. Aluminium sulphate and iron(II) sulphate have been used as precipitating agents. It was found that the addition of 30 mg 1⁻¹ aluminium gave 90 per cent removal of total phosphorus. The addition of 60 mg 1⁻¹ iron(II) gave 89 per cent removal of total phosphorus. The costs of these chemicals are 0·93 Ft m⁻³ for aluminium and 0·11 Ft m⁻³ for iron precipitants, resp. Thus the iron is significantly less expensive as a phosphorus precipitant.     

The effect of thermal hydrolysis pretreatment on the anaerobic degradation of nonylphenol and short-chain nonylphenol ethoxylates in digested biosolids

The presence of micropollutants can be a concern for land application of biosolids. Of particular interest are nonylphenol diethoxylate (NP₂EO), nonylphenol monoethoxylate (NP₁EO), and nonylphenol (NP), collectively referred to as NPE, which accumulate in anaerobically digested biosolids and are subject to regulation based on the environmental risks associated with them. Because biosolids are a valuable nutrient resource, it is essential that we understand how various treatment processes impact the fate of NPE in biosolids. Thermal hydrolysis (TH) coupled with mesophilic anaerobic digestion (MAD) is an advanced digestion process that destroys pathogens in biosolids and increases methane yields and volatile solids destruction. We investigated the impact of thermal hydrolysis pretreatment on the subsequent biodegradation of NPE in digested biosolids. Biosolids were treated with TH, anaerobic digestion, and aerobic digestion in laboratory-scale reactors, and NPE were analyzed in the influent and effluent of the digesters. NP₂EO and NP₁EO have been observed to degrade to the more estrogenic NP under anaerobic conditions; therefore, changes in the ratio of NP:NPE were of interest. The increase in NP:NPE following MAD was 56%; the average increase of this ratio in four sets of TH-MAD samples, however, was only 24.6 ± 3.1%. In addition, TH experiments performed in pure water verified that, during TH, the high temperature and pressure alone did not directly destroy NPE; TH experiments with NP added to sludge also showed that NP was not destroyed by the high temperature and pressure of TH when in a more complex sludge matrix. The post-aerobic digestion phases removed NPE, regardless of whether TH pretreatment occurred. This research indicates that changes in biosolids processing can have impacts beyond just gas production and solids destruction.     

Fate and removal of selected endocrine‐disrupting compounds in sewage using activated sludge treatment

The variation and fate of four endocrine‐disrupting compounds (EDCs) composed of 4‐n‐nonylphenol (4‐n‐NP), bisphenol A (BPA), 17β‐estradiol (E2) and 17α‐ethinylestradiol (EE2) were investigated along treatment units in a sewage treatment plant (STP), China with anaerobic, anoxic and aerobic activated sludge processes. The mean concentrations were 64.8 ng/L (E2), 115.3 ng/L (4‐n‐NP), 171.5 ng/L (EE2), and 920.7 ng/L (BPA) in the influents, and 22.8 ng/L (E2), 50.9 ng/L (4‐n‐NP), 49.9 ng/L (EE2), and 84.3 ng/L (BPA) in the effluents. The biological treatment was more effective in removing NP, BPA and E2 from the aqueous phase than the primary treatment, while the latter could effectively remove EE2. Their possible removal mechanisms during the biological treatment with activated sludge were further explored through spiked batch experiments under three oxygen‐supplying conditions (anaerobic, anoxic and aerobic). The batch experiments showed that 4‐n‐NP, E2 and BPA were removed from the aqueous phase through biodegradation. The combination of sludge sorption and biodegradation accounted for the removal of EE2. Anoxic activated sludge showed the most rapid degradation of 4‐n‐NP, while E2 could be removed most effectively by aerobic activated sludge, and sludge sorption had a remarkable effect on its removal within the initial 15 min of the experiments under three oxygen‐supplying conditions.     

Development of an advanced biological treatment system applied to the removal of nitrogen and phosphorus using the sludge ceramics

To develop a method of forming lake sediment into sludge ceramics with porosity and good biological adhesion for use as a medium for microorganisms in wastewater treatment, a study of the effects of forming conditions was conducted by adjusting the water content of sludge and compounding some additives. By adjusting the water content of the raw material at the kneading/pelletizing step to 40–42% and adding 3% waste glass to the raw materials to make up for the lack of flux, a sludge ceramic with a density in terms of specific gravity of saturated surface dry aggregate of about 1400 kg m⁻³ was formed. In addition, to develop a small-scale wastewater treatment system capable of removing nitrogen and phosphorus, a sludge ceramic was applied as a medium for biological filtration. The results indicated that the BOD removal nitrification rate were superior to those of conventional ceramic media, reached at 95.3% and 87.4%, respectively. The introduction of iron electrolysis resulted in high treatment performance achieving BOD levels of 10 mg L⁻¹ or less, T-N of 10 mg L⁻¹ or less and T-P of 1 mg L⁻¹ or less.     

Phthalates,nonylphenols and LAS in an alternately operated wastewater treatment plant--fate modelling based on measured concentrations in wastewater and sludge

The performance of an alternately operated activated sludge wastewater treatment plant (WWTP) has been investigated with respect to six phthalates, nonylphenol (NP) and nonylphenol diethoxylate (NPDE) and linear alkylbenzene sulphonates (LAS). Samples of raw sewage, primary and secondary sludge and treated water were collected during an 8-day period in May 1999 and analysed for dissolved and sorbed substances. To evaluate the system performance with respect to substance removal through biodegradation and sorption to sludge the measured data were applied in a model describing the different bioreactors as one single reactor, corresponding to the concepts of, e.g. SimpleTreat. The most abundant of the investigated phthalates was di-(2-ethylhexyl)-phthalate (DEHP) with a measured mean inlet flow of 240g/day. Two percent of this amount was found in the treated water, 70% was biodegraded and 28% was found in the sludge. For LAS the mean inlet flow was 20,300g/day, of which less than 1% was found in the treated water, 84% was biodegraded and 15% was found in the sludge. The mean inlet flow of NP and NPDE was 44 and 590g/day, of which 4% and 2% was found in the treated water, 80% was biodegraded for both substances, and 16% and 18% was found in the sludge, respectively. The WWTP removal of the investigated substances was thus high compared to other studies of conventional activated sludge WWTPs. The simple model set-up presents a strong tool for predicting substance removal and system sensitivity related to changes in the inlet conditions, such as concentrations and flow. Furthermore, it allows the inclusion of complex alternately operated WWTPs in risk assessment tools such as e.g. SimpleTreat.     

Complexation of copper in the effluent of a sewage treatment plant and an estimate of its influence on toxicity to coho salmon

Measurements by cupric ion electrode of the complexing capacity of the effluent from a sewage treatment plant (STPE) averaged 0.300 mg 1⁻¹. Of the complexed Cu 67% was due to compounds of 10,000 MW. Organic compounds removable by activated carbon composed 88% of the total organic carbon and were responsible for 87% of the complexation. Complexation of Cu²⁺ by STPE diminishes the toxicity from total Cu to juvenile coho salmon; the LC₅₀ was 0.164 mg 1⁻¹ for river water vs 0.286 mg 1⁻¹ for 40% STPE. The LC₅₀ of Cu²⁺ was approximately the same (0.017 vs 0.022 mg 1⁻¹) in both matrices; this species thus appears to play a toxic role. The mean survival time in diluted STPE with added Cu was inversely proportional to the Cu²⁺ concentration.     

Effect of settling on performance of the upflow anaerobic sludge bed reactors

The effects of settler volume on the start-up and steady-state performance of 41. laboratory upflow sludge bed reactors treating bean blanching waste of 10,000 mg COD l⁻¹ were determined. The rate of start-up, as well as the maximum loading rate, increased with increased settler volume and performance. A loading rate of 30 kg COD m⁻³ day⁻¹ (based on reactor volume alone) and a COD removal of 95% was obtained with a 21. settling flask and a 4 to 1 recirculation rate. Without a settler, the maximum loading rate was 10 kg COD m⁻³ day⁻¹. The sludge was flocculent rather than granular. Sludge profiles and characteristics in the reactors and settlers were determined.     

Removal of the endocrine disrupter nonylphenol and its estrogenic activity in sludge treatment processes

The estrogenic compound nonylphenol (NP) is frequently found in sludge from sewage treatment works. Hence, when sewage sludge is spread on the land, endocrine-disrupting compounds may get into the soil. The goal of this study was to investigate the extent to which aerobic mesophilic treatment in continuous reactors permits the removal of NP from sludge and how this process may be useful for treating anaerobically stabilised sludge. We also report on the behaviour of NP during the anaerobic treatment of sludge. The reduction in sludge estrogenic activity observed in the different types of treatment, as measured using estrogen-responsive reporter cells lines (MELN bioassay), was compared with NP removal rates. Under anaerobic conditions, no degradation of NP and its estrogenic activity was observed. Indeed, an accumulation of the compound occurred. In contrast, high removal of NP was achieved in aerobic conditions as well as in aerobic Post-treatment of anaerobically pre-digested sludge, with a concomitant reduction of the sludge's estrogenic potency.     

Comparing steroid estrogen, and nonylphenol content across a range of European sewage plants with different treatment and management practices

The effluent of 17 sewage treatment works (STW) across Norway, Sweden, Finland, The Netherlands, Belgium, Germany, France and Switzerland was studied for the presence of estradiol (E2), estrone (E1), ethinylestradiol (EE2) and nonylphenol (NP). Treatment processes included primary and chemical treatment only, submerged aerated filter, oxidation ditch, activated sludge (AS) and combined trickling filter with activated sludge. The effluent strength ranged between 87 and 846 L/PE (population equivalent), the total hydraulic retention time (HRT) ranged between 4 and 120 h, sludge retention time (SRT) between 3 and 30 d, and water temperature ranged from 12 to 21 °C. The highest estrogen values were detected in the effluent of the STW which only used primary treatment (13 ng/L E2 and 35 ng/L E1) and on one occasion in one of the STW using the AS system (6.5 ng/L E2, 50.5 ng/L E1, but on three other occasions the concentrations in this STW were at least a factor of 6 lower). For the 16 STW employing secondary treatment E2 was only detected in the effluent of six works during the study period (average 0.7-5.7 ng/L). E1 was detected in the effluent of 13 of the same STW. The median value for E1 for the 16 STW with secondary treatment was 3.0 ng/L. EE2 was only detected in two STW (1.1, <0.8-2.8 ng/L). NP could be detected in the effluent of all 14 STW where this measurement was attempted, with a median of 0.31 μg/L and values ranging from 0.05 to 1.31 μg/L. A comparison of removal performance for E1 was carried out following prediction of the probable influent concentration. A weak but significant (α<5%) correlation between E1 removal and HRT or SRT was observed.     

Anaerobic biological treatment of phenol at 9.5-15 degrees C in an expanded granular sludge bed (EGSB)-based bioreactor

The aims of this study were to demonstrate the (1) feasibility of psychrophilic, or low-temperature, anaerobic digestion (PAD) of phenolic wastewaters at 10–15 °C; (2) economic attractiveness of PAD for the treatment of phenol as measured by daily biogas yields and (3) impact on bioreactor performance of phenol loading rates (PLRs) in excess of those previously documented (1.2 kg phenol m⁻³ d⁻¹). Two expanded granular sludge bed (EGSB)-based bioreactors, R1 and R2, were employed to mineralise a volatile fatty acid-based wastewater. R2 influent wastewater was supplemented with phenol at an initial concentration of 500 mg l⁻¹ (PLR, 1 kg m⁻³ d⁻¹). Reactor performance was measured by chemical oxygen demand (COD) removal efficiency, CH₄ composition of biogas and phenol removal (R2 only). Specific methanogenic activity, biodegradability and toxicity assays were employed to monitor the physiological capacity of reactor biomass samples. The applied PLR was increased to 2 kg m⁻³ d⁻¹ on day 147 and phenol removal by day 415 was 99% efficient, with 4 mg l⁻¹ present in R2 effluent. The operational temperature of R1 (control) and R2 was reduced by stepwise decrements from 15 °C through to a final operating temperature of 9.5 °C. COD removal efficiencies of c. 90% were recorded in both bioreactors at the conclusion of the trial (day 673), when the phenol concentration in R2 effluent was below 30 mg l⁻¹. Daily biogas yields were determined during the final (9.5 °C) operating period, when typical daily R2 CH₄ yields of c. 3.3 l CH₄ g⁻¹ COD_removed d⁻¹ were recorded. The rate of phenol depletion and methanation by R2 biomass by day 673 were 68 mg phenol g VSS⁻¹ d⁻¹ and 12–20 ml CH₄ g VSS⁻¹ d⁻¹, respectively.     

Phytoplankton biomass and production in the river meuse (Belgium)

The biomass and production of the phytoplankton in a relatively unpolluted reach of the River Meuse (Belgium) were followed through two years (1983 and 1984). Chlorophyll a varied from 0.2 to about 120 mg m⁻³, and production ranged between 0.05 and 5.78 gC m⁻² d⁻¹. The mean photosynthetic quotient (PQ) was 1.25.

The parameters of the light-photosynthesis relationship (P_opt and l_k) were calculated and related to the variations of temperature and light in the water column. A simple model allowed calculations of the annual production, which was estimated to be 494 gC m⁻² yr⁻¹ in 1983 and 547 gC m⁻² yr⁻¹ in 1984.

Finally, a simple model is developed, which explains the relationship between phytoplankton development and discharge; this model shows how the effect of discharge can be described by a “dilution rate” of the plankton growing in the river water.     

The long-term nutrient accumulation with respect to anthropogenic impacts in the sediments from two freshwater marshes (Xianghai Wetlands, Northeast China)

Sediment cores, representing a range of watershed characteristics and anthropogenic impacts, were collected from two freshwater marshes at the Xianghai wetlands (Ramsar site no. 548) in order to trace the historical variation of nutrient accumulation. Cores were ²¹⁰Pb- and ¹³⁷Cs-dated, and these data were used to calculate sedimentation rates and sediment accumulation rates. Ranges of dry mass accumulation rates and sedimentation rates were 0.27–0.96 g m⁻² yr⁻¹ and 0.27–0.90 cm yr⁻¹, respectively. The effect of human activities on increased sediment accumulation rates was observed. Nutrients (TOC, N, P, and S) in sediment were analyzed and nutrient concentration and accumulation were compared in two marshes with different hydrologic regime: an “open” marsh (E-0) and a partly “closed” marsh (F-0). Differences in physical and chemical characteristics between sediments of “open” and partly “closed” marsh were also observed. The “open” marsh sequestered much higher amounts of TOC (1.82%), N (981.1 mg kg⁻¹), P (212.17 mg kg⁻¹), and S (759.32 mg kg⁻¹) than partly “closed” marsh (TOC: 0.32%, N: 415.35 mg kg⁻¹, P: 139.64 mg kg⁻¹, and S: 624.45 mg kg⁻¹), and the “open” marsh indicated a rather large historical variability of TOC, N, P, and S inputs from alluvial deposits. Nutrient inputs (2.16–251.80 g TOC m⁻² yr⁻¹, 0.43–20.12 g N m⁻² yr⁻¹, 0.39–3.03 g P m⁻² yr⁻¹, 1.60–15.13 g S m⁻² yr⁻¹) into the Xianghai wetlands of China are in the high range compared with reported nutrient accumulation rates for freshwater marshes in USA. The vertical variation, particularly for N, P, and S indicated the input history of the nutrients of the Xianghai wetlands developed in three periods—before 1950s, 1950–1980s, and after 1980s. The ratios between anthropogenic and natural inputs showed that the relative anthropogenic inputs of TOC, N, P, and S have been severalfold (TOC: 1.68–11.21, N: 0.47–3.67, P: 0.24–1.36, and S: 1.46–2.96) greater than values of their natural inputs after 1980s. The result is probably attributable, in part, to two decades of surface coal mining activities, urban sewage, and agriculture runoff within the upstream region of the Huolin River. Our findings suggest that the degree of anthropogenic disturbance within the surrounding watershed regulates wetland sediment, TOC, N, P, and S accumulation.     

Removal of indigenous rotaviruses during primary settling and activated-sludge treatment of raw sewage

An eight month study of indigenous rotavirus removal during primary settling and activated sludge treatment of raw sewage was made in a plant in Houston, Texas treating 1.5 million gal day⁻¹. An average reduction of 44–55% was obtained by primary settling and a 93–99% reduction was achieved in final chlorinated effluents. Composite sampling at 1 h intervals over a 24 h period indicated average removals of 85% compared to a misleading 6% indicated by one set of grab samples of raw sewage and effluent collected simultaneously. Quantification of rotaviruses was made by immunofluorescent foci counts 24 h after addition of sample concentrates to coverslip cultures of fetal rhesus kidney cells. Rotaviruses varied from 40–5101⁻¹ of raw sewage and from 0 to 25 in the final chlorinated effluent.