Adaptation of methanogenic sludge to high ammonia-nitrogen concentrations

The influence of ammonia-nitrogen concentrations in excess of 1500 mg 1⁻¹ on the methane formation from volatile fatty acids by two types of methanogenic sludge was investigated in batch experiments. One was digested sewage sludge, acclimated to 815 mg 1⁻¹ ammonia-nitrogen and the other was digested piggery manure, acclimated to an ammonia-nitrogen concentration of 2420 mg 1⁻¹. In the experiment with digested sewage sludge, methane formation took place still at an ammonia-nitrogen concentration as high as 5 g 1⁻¹. However, an increasing lag-phase was observed at increasing ammonia-nitrogen concentrations in the range 730–4990 mg 1⁻¹. On the other hand in digested piggery manure methane formation immediately started without any lag-phase in the ammonia-nitrogen concentration range of 605–3075 mg 1⁻¹. In the experiments with both types of sludge the maximum methane formation rate slowly decreased with increasing ammonia-nitrogen concentrations.     

Assessment of metal mobility in dredged harbour sediments from Barcelona, Spain

In order to assess heavy metal mobility in dredged harbour sediments, six superficial sediment samples covering a range of pollution levels and environments were collected in Barcelona Harbour. Samples were characterised in terms of major compounds (Al, Ca, Fe, Mn, Si, Ti, Mg, K and Na); total C, N and S contents; organic matter; and water content. Pseudo-total trace metal contents were assessed after aqua regia digestion (ISO 11466:1995). The modified BCR three-step sequential extraction procedure (BCR-SEP) was applied, and both major compounds (Al, Ca, Fe and Mn) and trace metals (Cd, Cr, Cu, Ni, Pb and Zn) were determined in the different extracts. Both the pseudo-total digestion method and the BCR-SEP were validated using two sediment certified materials from lakes (BCR CRM 701 and BCR CRM 601). The highest metal concentrations were observed in one of the sampling points which receives an urban discharge. The observed mobility order (percentage of metal extracted in the first step) of the six trace metals studied was Cd>Zn>Pb>Cu>Ni>Cr. The good agreement observed with the results obtained as the sum of the four steps (extractable+residue) and the pseudo-total content shows that laboratory working conditions were under control.     

Bioleaching of metals from sewage sludge: Microorganisms and growth kinetics

Microbial leaching is one of the advantageous methods of removing heavy metals from sewage sludge, however, the microbiological aspects of this technology have not been studied. This study presents the characterization of the naturally occurring microorganisms, responsible for the metal leaching activity, in 21 different sewage sludges. The results obtained indicate that the bioleaching of metals is carried out by successive growth of less-acidophilic and acidophilic thiobacilli. Several species of less-acidophilic thiobacilli participate in the sludge acidification, but Thiobacillus thioparus is the most important species. In contrast, Thiobacillus thiooxidans seems to be the only species involved in the acidophilic group of thiobacilli. The growth kinetics of the two groups of thiobaciili was followed in five different sewage sludges. After 5 days of incubation in shake flasks, the pH of the sludge was decreased to about 2.0 and this pH decrease solubilized the toxic metals (Cd: 83–90%; Cr: 19–41%; Cu: 69–92%; Mn: 88–99%; Ni: 77–88%; Pb: 10–54%; Zn: 88–97%). The maximum specific growth rate (μ_max) for the less-acidophilic thiobacilli varied between 0.079 and 0.104 h⁻¹ and that for the acidophilic thiobacilli varied between 0.067 and 0.079 h⁻¹.     

Removal of organic acids by activated sludges

Removal of coexisted volatile organic acids was studied using three kinds of activated sludges; treated with sewage, digested night soil and undiluted night soil at the plant scale and laboratrial experiment. Concentration of volatile fatty acids in sewage were too low to be detected, meanwhile 5–28 ppm of acetic acid were detected in influent of aeration tank of digested night soil treatment plant, and 1335–5340 ppm of acetic acid were detected in night soil. Removal rates of acetic acid were 35.9 mg g⁻¹ h⁻¹ by sewage activated sludge, 33.6 mg g⁻¹ h⁻¹ by digested night soil activated sludge and 16.9 mg g⁻¹ h⁻¹ by undiluted night soil activated sludge under coexisting volatile fatty acids. This difference depends on the number of bacteria in the activated sludge. Dissimilation percentage of acetic, propionic, butyric and valeric acids were similar results in these activated sludges.     

Mercury concentrations in fish inhabiting two polluted lakes in Northern Canada

The concentrations of total mercury in the sediments, water and fish of Giauque Lake and Thompson Lake in northern Canada were determined during 1977 and 1978. Both lakes had formerly received mercury-laden industrial discharges, which were terminated in 1968 (Giauque Lake) and 1949 (Thompson Lake). In Giaque Lake, lake trout (Salvelinus namaycusy) contained an average of 3.79 mg kg⁻¹ in their muscle while the average concentrations in northern pike (Esox lucius) and round whitefish (Prosopium cylindraceum) were 1.75 and 1.22 mg kg⁻¹ respectively. About 7% of the lake's bottom contained mercury levels of > 500 μg kg⁻¹ (dry weight) but, in the water, concentrations were always below detectable limits (0.2 μg l⁻¹). In Thompson Lake, mercury levels in northern pike averaged 1.69 mg kg⁻¹, whereas in lake whitefish (Coregonus clupeaformis), the highest recorded value was 0.6 mg kg⁻¹. Although mercury was usually not detectable in the water column, there was heavy contamination of the sediments, with values reaching 1300 μg kg⁻¹. In addition, approximately 15% of the lake bottom contained mercury in excess of 500 μg kg⁻¹. Based on these data, it is concluded that: (1) northern pike are still accumulating mercury from exposed tailings which were deposited in Thompson Lake 30 years ago, and (2) contamination of only a small part of a lake may result in high levels in fish throughout the lake: this is probably due to the movement of fish from contaminated to noncontaminated areas.     

Distribution of total mercury in the fishes of Lake Oahe

In 1971, a joint Federal-State survey was conducted to investigate the total mercury content of fish and sediment in Lake Oahe, South Dakota. Average total mercury concentration of 225 fish flesh samples was 0.27 mg kg⁻¹; game fish samples averaged 0.31 mg kg⁻¹ and nongame fish samples averaged 0.22 mg kg⁻¹. Frequency distributions of total mercury concentrations in the fish are presented by fish species and sampling location. Data include total mercury analyses of 43 sediment samples.     

Nitrification kinetics in activated sludge at various temperatures and dissolved oxygen concentrations

Activated sludge from a domestic sewage works was enriched with nitrifying bacteria by running a laboratory fermenter on ammonia-supplemented sewage. This enriched culture was used to determine respirometrically the kinetics of microbial nitrification. It was demonstrated that the reaction fits the Michaelis-Menten model for temperatures from 10 to 35°C, having a temperature optimum at 15°C (K₃ 0.72 mg 1⁻¹ NH₃). Nitrification is unaffected by high dissolved oxygen concentration 38 mg 1⁻¹ O₂ at 30°C) after acclimatisation. Nitrite concentrations > 20 mg 1⁻¹ are inhibitory to the reaction.     

Removal of heavy metals from electroplating rinsewaters by precipitation, flocculation and ultrafiltration

Chromium, nickel, copper and zinc can be effectively removed from electroplating rinsewaters by hydroxide precipitation, flocculation and ultrafiltration. Prior to precipitation, chromium is reduced from the hexavalent to the trivalent form by ferrous sulfate and cyanide in copper and zinc rinsewaters are oxidized by sodium hypochlorite. Minimum metal concentrations in the permeate from separate batches of chromium, nickel, copper and zinc rinsewaters were found to be, respectively, 0.17 mg 1⁻¹ Cr (T), 0.26 mg 1⁻¹ Ni, 0.30 mg 1⁻¹ Cu and 1.84 mg 1⁻¹ Zn. These solubilities are in good agreement with the theoretical solubility curves, except for copper where the formation of stable copper cyanide complexes appears to increase the solubilities at least two orders of magnitude relative to those predicted on the basis of the equilibrium constants for copper hydroxides and oxides. A simple mass balance model, assuming concentrate recycle and constant metal concentration in the permeate, is adequate for the prediction of feed and permeate concentrations as a function of the volume filtered up to a relative volume of about 0.3. Above this value, the feed concentrations are lower than predicted, apparently because of entrapment of metal precipitate in the strainer. Water recoveries are strongly dependent on the specific metal removed and are found to be 24% for Ni with a 0.20 μm membrane, 10% for Cr with a 0.80 μm membrane, 6.5% for Cu and 3.7% for Zn, both with a 0.45 μm membrane.     

Effects of microelements on soil nematode assemblages seven years after contaminating an agricultural field

Long-term effects of Cd, Cr, Cu, Se and Zn were studied 7 years after artificially contaminating plots of an agricultural field on a calcareous chernozem soil. Effects of three to four different contamination levels (originally 10, 30, 90 and 270 mg kg⁻¹) were studied. Nematode density was significantly reduced by 90 and 270 mg kg⁻¹ Se as well as by 270 mg kg⁻¹ Cr, while 90 and 270 mg kg⁻¹ Se also reduced nematode generic richness. Maturity Index values (calculated for c-p 2–5 nematodes) consistently decreased with increasing Cr and Se concentration and to a lesser extent in Zn plots as well. Structure Index showed decreasing trends in increasing Cr, Se and (to a lesser extent) in Zn treatments, while in Cd it shows a moderate increase. Distribution of c-p groups was negatively affected by the increasing Cr and Se concentration, while in Zn plots, this decrease was not significant. Response of feeding groups to pollutions was similar to other parameters: Cr and Se caused significant changes toward the loss of variability. The proportion of the most sensitive omnivorous and predatory nematodes decreased clearly as a consequence of Cr and Se treatments. Zn pollution also resulted in a slight decrease in this group, while Cd caused an increase. Nematode diversity profiles showed a significant decrease in the plots of increased Cr and Se concentrations, while increased concentrations of Cu and Zn resulted in ambiguous effects. Besides providing evidence on the harmful effects of Cr and Se on a soil nematode assemblage, our results suggest that simultaneous analysis of Maturity Index, Structure Index and diversity profiles provide a promising tool in nematological indication of soil pollution.     

Zinc, cadmium and lead in water, sediments and submerged plants of the Derwent Reservoir, Northern England

A partial budget is presented of the zinc, cadmium and lead entering the Derwent Reservoir. The mean levels in the water column upstream of the site of inflow are: Zn, 0.216 mg 1⁻¹ ; Cd, 0.003 mg 1⁻¹; Pb, 0.065 mg 1⁻¹; the levels after passage through the 4.1 km² reservoir fall by: Zn, 70.3%; Cd, 98.3%; Pb, 89.2%. Most of these metals are deposited in sediments, the mean values for which are: Zn, 1035 μg⁻¹; Cd, 13μg⁻¹; Pb, 827μg⁻¹. Lead, a higher percentage of which occurs as particulate material, is deposited more rapidly than zinc; this effect is especially obvious when streaming of colder water along the bottom of the reservoir takes place at the time of floods. Macroscopic plants are only occasional in this reservoir, due perhaps in part to heavy metal toxicity. Of the two most common submerged species, Nitella flexilis probably accumulates almost all of its metal content directly from the water, but the data suggest that sediments are a source of some of the heavy metals accumulated by Glyceria fluitans.     

The effect of sewage sludge land disposal on the microbiological quality of groundwater

The long term effect of farmland disposal of anaerobically digested sewage sludges (alum, iron and lime) on the microbiological quality of groundwater was investigated using the lysimeter system. It was observed that after 4 years of heavy sludge application (5100 kg TKN ha⁻¹ 4 yr⁻¹), 92–98% of the sewage micoorganisms in the sludge had perished in the soils systems. Analyses of leachates and soils for coliforms and heterotrophic bacterial populations revealed that there was little possibility of microbiological contamination of groundwater by the practice of sludge farmland disposal, provided that the groundwater table was not too high and the soil was well-drained.     

Sorption and bioavailability of heavy metals in long-term differently tilled soils amended with organic wastes

In this study, bioavailability and enrichment studies were focused on Cd, Zn and Cu in two different soils (sandy loam and silt loam), which were treated with compost and sewage sludge, respectively, both under conventional tillage (CT) and no tillage (NT). Long-term NT resulted in a significant increase in Cd and Zn extracted by aqua regia in a soil profile (0-25 cm), especially in the 0-3 cm layer. In the sandy loam, a slight increase in cadmium due to sewage sludge application was observed. Results from EDTA-extractable heavy metal analyses were not consistent but NH(4)NO(3)-extractable concentrations were significantly lower in the NT soil. Bioavailability of heavy metals was reduced in the long-term NT, resulting in lower uptake of Cd and Zn by plants and accumulation in the soil. The effect of tillage on enrichment of heavy metals in soils was more significant than the impact of the fertilisation by means of legally allowable application rates of organic wastes. This work suggests that non-tilled soils enriched in heavy metals should not be amended with organic waste in the long term.     

Direct analytical procedure for determination of volatile organic acids in raw municipal wastewater

A direct analytical method for identification and determination of the individual volatile acids in raw sewage was developed. The proposed procedure is rapid, omitting tedious sample pretreatment and thus avoiding possible losses involved in steam distillation, evaporation or extraction. It consists of direct injection of raw sewage into a gas chromatograph, including Carbowax 20 M on acid washed Chromosorb W column and a flame ionization detector. Sample preparation is confined to addition of solid metaphosphoric acid to the raw sewage, and removal of precipitated proteins and suspended solids by centrifugation.The direct injection method proved to be practicable, accurate and rapid. Volatile acids content in raw municipal sewage in Haifa, Israel, was found to be in the range of 150–160 mg l⁻¹, of which 120–125 mg l⁻¹ was acetic acid, 30–33 mg l⁻¹ propionic acid, 6–8 mg l⁻¹ butyric acid, 2 mg l⁻¹ isovaleric acid, and 0.5–1 mg l⁻¹ valeric acid.     

Variation of sludge volume index with activated sludge characteristics

Activated sludge samples from 2 laboratory units and 12 sewage treatment plants were examined to determine the effect of filamentous microorganisms, floc size and suspended solids concentration on SVI. An attempt was also made to correlate SVI to zone settling velocity. At a suspended solids concentration range of 700–4800 mg 1⁻¹ there was no effect of filamentous microorganisms at filament length concentrations below 10⁷μm (mg SS)⁻¹. However, when it was over 10⁷ μm (mg SS)⁻¹ SVI increased sharply with increasing concentrations of filamentous microorganisms.At all suspended solids concentrations examined SVI varied with floc size at filament length concentrations below 10 μm (mg SS)⁻¹. But, at filament length concentrations higher than this level, no effect of floc size on SVI was observed.The effect of suspended solids concentration on SVI was examined at different levels of filament lengths. It was found that the shape of SVI-suspended solids concentration curve varied with the level of filament lengths. A well defined relationship was found between SVI and zone settling velocity at all suspended solids concentrations examined.     

Anaerobic degradation of nonionic and anionic surfactants in enrichment cultures and fixed-bed reactors

Anaerobic biodegradation and inhibitory effects of nonionic and anionic surfactants on methanogenic fermentation were tested in incubation experiments with anoxic sediment samples and sewage sludge. Alkylsulfonates and alkylbenzenesulfonates were not degraded but inhibited methanogenesis from sludge constituents at concentrations ≥10 mgl⁻¹. Sodium dodecylsulfate was at least partly degraded after adaptation at concentrations 100 mgl⁻¹ and the sulfate group was reduced to sulfide. The polyethyleneglycol moiety of alkylphenolethoxylates was fermented to methane at concentrations 500 mgl⁻¹ whereas the alkylphenol residue probably remained unchanged. Alkylethoxylates were completely degraded to methane and CO₂ at concentrations up to 1.0 gl⁻¹. Complete anaerobic degradation of this surfactant type to methane, CO₂, and traces of acetate and propionate was demonstrated in a lab scale anaerobic fixed-bed reactor, either with prereduced mineral salts medium or with air-saturated artificial wastewater. This process lends itself as a suited, inexpensive means for treatment of wastewaters containing enhanced loads of nonionic surfactants, e.g. from the surfactant manufacturing or processing industry.     

Particulate and dissolved trace metals in Lake Ontario

Particulate metal concentrations in the nearshore waters of Lake Ontario have been determined to be 690 ng l⁻¹ for Cu; 40 ng l⁻¹ for Cd; 180 ng l⁻¹ for Ni; 1690 ng l⁻¹ for Zn; 2100 ng l⁻¹ for Mn; and 700 μg l⁻¹ for Fe. These values are considerably higher than the particulate metal concentrations in the offshore waters: 130, 8, 34, 230, 110, 260 and 9000 ng l⁻¹ for Cu, Cd, Ni, Zn, Pb, Mn and Fe respectively. In general, 50–80% of the Cu, 10–40% of the Ni, 20–60% of the Cd and >60% of the Pb in the lake water were bound to the suspended particulates. From the standing crop of the particulate metals and the estimated rates of their deposition on the lake bottom, the residence times of the particulate metals in the lake water column have been estimated to be about 0.5 yr. on the average. The suggestion is made that particulate organic matter may be an important vehicle for metal transport to the Lake Ontario sediments.     

Environmental chemistry of copper in Lake Monona, Wisconsin

Lake Monona, located at Madison, Wisconsin, received over 1.5 × 10⁶ pounds of copper sulfate in the past 50 yr to control excessive algal growth. Dissolved copper on Lake Monona epilimnion is inversely related to pH which indicates possible control of dissolved copper by basic copper carbonate. Concentrations as high as about 4 μg Cu l⁻¹ were found in Lake Monona epilimnion, which also contains 3.3 me l⁻¹ (milliequivalents per liter) of alkalinity, mostly bicarbonate. Concentrations of dissolved copper were consistently lower (0.3 μg Cu l⁻¹) in the hypolimnion. Sulfide probably controls dissolved copper in the hypolimnion during anoxic conditions because of sulfide insolubility. Particulate copper concentrations of about 3 μg l⁻¹ increased slightly with depth. The highest concentrations of copper in Lake Monona sediments (650 mg kg⁻¹) were found approximately 60 cm below the current sediment surface. Surface sediments of Lake Monona contained approximately 250 mg Cu kg⁻¹ sediment dry weight.     

Concentrations of nitrilotriacetate and certain metals in Canadian wastewaters and streams: 1971–1975

At 13 Ontario cities, representing a variety of populations and sewage treatment processes, grab samples were taken from the sewage treatment plant influent and effluent and from the receiving stream above and below the sewage outfall. The samples, taken once each month from November 1971 to March 1975 were analyzed for nitrilotriacetate (NTA), 9 metals, and phosphorus. From April 1971 to January 1973 household detergents in Canada contained an average of 6% NTA; after March 1973 they contained 15%. This increased usage of NTA was reflected in the NTA content of sewage influents, which rose from a median level of 1.3 mg l⁻¹ before the change to 3.2 mg l⁻¹ after the change. NTA levels in sewage effluent also increased somewhat, but much of the NTA disappeared in the sewage treatment processes. Even with the increased usage of NTA, the receiving streams below the sewage outfall contained only low levels of NTA: 97% of all samples during this period contained less than 0.5 mg l⁻¹, and the median concentration was 0.05 mg l⁻¹. Phosphorus concentrations in the sewages decreased at the time detergent compositions changed. Comparison of metal concentrations before and after the change, as well as metal-NTA correlation coefficients, failed to show clear evidence of an association between NTA concentration and metal concentration.     

Screening of antimycotics in Swedish sewage treatment plants - Waters and sludge

Concentrations of six pharmaceutical antimycotics were determined in the sewage water, final effluent and sludge of five Swedish sewage treatment plants (STPs) by solid phase extraction, liquid/solid extraction, and liquid chromatography-electrospray tandem mass spectrometry. The antimycotics were quantified by internal standard calibration. The results were used to estimate national flows that were compared to predictions based on sales figures. Fluconazole was the only one of the six investigated antimycotics that was detected (at concentrations ranging from 90 to 140 ng L⁻¹) in both raw sewage water and final effluent. Negligible amounts of this substance were removed from the aqueous phase, and its levels were below the limit of quantification in all of the analyzed sludge samples. In contrast, clotrimazole, ketoconazole and econazole were present in all of the sludge samples, at concentrations ranging between 200 and 1000 μg kg⁻¹, dry weight. There were close correlations between the national measured and predicted antimycotic mass flows. Antimycotic fate analysis, based on sales figures, indicated that 53% of the total amount of fluconazole sold appeared in the final effluents of the STPs, while 1, 155, 35, 209 and 41% of the terbinafine, clotrimazole, ketoconazole, econazole and miconazole sold appeared in the digested dewatered sludge.     

Role of bacterial extracellular polymers in metal uptake in pure bacterial culture and activated sludge—II Effects of mean cell retention time

A gel filtration technique afforded a good separation between metal complexed with bacterial extracellular polymers and free metal ions. The complexation of polymers extracted from cultures of Klehsiella aerogenes and activated sludge with cadmium, nickel, manganese and cobalt was demonstrated. The extraction of extracellular polymers from cultures of K. aerogenes and activated sludge reduced the capacity of the cells and flocs to adsorb metal. Adsorption and complexation of metals by cells of K. aerogenes and extracellular polymers extracted from activated sludge were fitted to Freundlich equilibrium isotherms. Saturation of activated sludge polymer binding sites occurred at 10 mg 1⁻¹ metal additions for all the metals studied except manganese which was complexed to a very limited extent. Cells of K. aerogenes exhibited no saturation effects in the range of metal concentrations studied.Precipitation of metals below a concentration of 1 mg 1⁻¹ was minimal, with the exception of cadmium precipitation. At a concentration of 10 mg 1⁻¹, precipitation of cadmium, cobalt and manganese may have been the major mechanism of metal removal. The more soluble metals generally displayed the lowest removals. Concentrations of extracellular polymers and soluble chelating agents may be important in controlling removals of metals which are largely soluble in activated sludge.