Bromide concentration in Swedish precipitation, surface and ground waters

The occurrence of bromide in precipitation, surface and ground waters in Sweden has been investigated (300 samples). The concentration of bromide in precipitation is 0.05–0.15 μM in the south and <0.05 μM in the north of Sweden. The concentrations of bromide and chloride are well correlated. For river water the same areal distribution pattern as for precipitation is found, but the concentrations are 2–4 times higher. The molar ratio Br/Cl is 1 × 10⁻³ which is lower than that for sea water (1.54 × 10⁻³) and, most likely, also lower than for precipitation. A detailed study of Lake Mälaren has been made. The north-eastern feeder streams, passing an area of post-glacial clay, showed unusually high bromide concentrations (0.3–3 μM) and Br/Cl quotients (2 × 10⁻³-8 × 10⁻³). No correlation between the concentrations of bromide and chloride was found. Rough calculations indicate that fertilizers and chemicals added to the fields could only contribute a minor fraction of the bromide found. Analysis of 18 ground water samples indicated increased bromide levels as compared to surface waters.     

Detoxification of seawater used for gas scrubbing in the steel industry

Cyanide ion present in seawater after scrubbing blast furnace and coke ovens gases can be removed by sedimentation of hexacyanoferrate complexes followed by oxidation of residual cyanide with Caro's acid. Zinc ion is removed at the same time by adsorption on the hexacyanoferrate/hydrous ferric oxide precipitate.Sulphide is precipitated as ferrous sulphide, then oxidised by atmospheric oxygen. At 25°C and using an Fe/CN ratio of 1·00, initial concentrations of 50 mg l⁻¹ of CN⁻ and 10 mg l⁻¹ of Zn²⁺ in seawater are reduced to 5–7 mg l⁻¹ and 0·1 mg l⁻¹. Subsequent treatment with H₂SO₅/CN = 1·2 reduces the [CN⁻] to 0·1 mg l⁻¹.Treatment of a combined blast furnace/coke ovens effluent ([CN⁻] = 24 mgl⁻¹, [Zn²⁺] = 4·0 mgl⁻¹) with Fe/CN = 1·5 reduced [CN⁻] to 0·2 mg l⁻¹ and [Zn²⁺] to <0·1 mgl⁻¹. Subsequent treatment with H₂SO₅/CN = 2·0 reduced [CN⁻] to 0·2 mg l⁻¹. The process operates best in the pH range 7–9 and so is not affected by the buffer characteristics of seawater.     

The occurrence and removal of nitrogen in subsurface agricultural drainage from the San Joaquin Valley, California

During the years 1967–1973 there have been extensive studies of subsurface agricultural drainage in the San Joaquin Valley of California. These studies, by cooperating state and federal agencies, were to determine the composition and quantity of drainage waters produced from irrigated agriculture, to evaluate possible methods of removing problem constituents (mainly nitrogen) from these waters, and to obtain an idea of the effectiveness of the treatment methods studied for reducing the waters biostimulatory content with respect to potential receiving waters. The results of the studies indicated that on an annual average, the drainage waters will probably contain about 20 mg NO₃-N I⁻¹ even after 50 years of leaching and that most of the nitrogen is derived from native soil nitrogen. Treatment studies demonstrated that the nitrogen could be reduced from 20 to 3–5 mg N I⁻¹ by any one of several biological treatment processes including bacterial denitrification (filter and pond), algae growth and harvesting, and by a combination plant growth—bacterial denitrification (“symbiotic”) process. Cost estimates for the processes studied ranged from $10 to $36 1000⁻¹ m³ (1969 dollars). Laboratory algal assays demonstrated that the nitrogen removal systems studied effectively reduced the drainage waters biostimulatory content.     

Utilisation de la clinoptilolite en potabilisation des eaux—elimination de l'ion NH4

The objective of this study is to develop a technique to remove ammonium ion from water intended for potable purposes. An ion exchange method is used with a selective ion exchanger, a natural cation zeolite, clinoptilolite. Glass columns (Fig. 1) are used for laboratory experiments. These experiments show that the NH₄⁺ exchange capacity is very small compared to its total capacity 2.17 meq g⁻¹; its value depends essentially on the NH₄⁺ initial concentration and less on the Ca²⁺ concentration in the influent water. Figure 3 illustrates the practical exchange capacity relative to the initial concentration of ammonium ion for a soft water (Ca²⁺ = 35–50 mg l⁻¹). We were particularly interested in waters weak in ammonium ion concentration (NH₄⁺ = 1–3 mg l⁻¹). In this case and for 1 and 2 mg l⁻¹ NH₄⁺ concentration in water, the practical capacity is only 0.06 and 0.108 meq g⁻¹ respectively. The leakage is smaller than the ECC limit (European Community Council) for drinking waters (NH₄⁺ 0.5 mg l⁻¹) and the treated volume of water to breakthrough, defined at 0.5 mg l⁻¹ of NH₄⁺, is 720 BV (BV = bed volume) in both cases.In another way Fig. 6 shows that hard waters (due to Ca²⁺ ions) are more difficult to treat than soft waters. The practical capacity is smaller than before and the NH₄⁺-leakage is greater. To lessen NH₄⁺-leakage to less than 0.5 mg l⁻¹ for soft waters down-flow and up-flow, regeneration is used. Figure 7 shows that up-flow regeneration is more attractive than down-flow regeneration.Cycle reproducibility (Figs 4 and 5) shows that the regeneration conditions satisfied our requirements: in this case, the salt consumption is 180 eq of salt per eq of NH₄⁺ eliminated. This prompted us to try to reuse the regenerant (with NH₄⁺ ion). An increase of NH₄⁺-leakage is noticed in the presence of an NH₄⁺-residual in the regenerant. This increase is more significant with down-flow regeneration.After these laboratory experiments, we carried out a semi-industrial pilot-plant. Our objective was first to verify the laboratory results and secondly to study clinoptilolite behaviour relative to the time it was used. Two plexiglass columns comprise the pilot-plant shown in Fig. 9; soft water is used for these experiments. The first column is regenerated with fresh salt solution. The cycles obtained, considering their initial NH₄⁺-concentration, are reproduced in Fig. 10. For 2 mg l⁻¹ NH₄⁺ in the influent water, the leakage is about 0.2 mg l⁻¹ and the treated volume to breakthrough (0.5 mg l⁻¹ of NH₄⁺) is about 750 BV. The second column is regenerated with a recycled solution. The quality of the cycles decreases with the number of reuse of the regenerant as shown in Fig. 11. Nevertheless, it is interesting to note that after 3 reuses, the performance decrease is only 25% and the leakage, although it increases is smaller than 0.5 mg l⁻¹.Pilot results allowed us to propose a treatment of 30,000 m³ day⁻¹; the cost per cubic meter water treated, relative to NH₄⁺-removal, is about 0.165 FF (0.033 US $) for a plant and 0.77 FF (0.014 US $) for the same plant at the seaside. Using two serial columns decreased the cost by about 40–50%.     

An automated procedure for the determination of total Kjeldahl nitrogen

A procedure for the determination of total Kjeldahl nitrogen in surface fresh waters and organic wastes is described. Organic nitrogen compounds are converted to ammonium sulphate by a catalytic (red mercuric oxide) acid-sulphate digestion. The digest time is 3 h and allows for a maximum of 36 samples, 2 blanks and 2 standards to be processed simultaneously. There is no pH adjustment required following the digestion. Calibration curves covering the ranges (i) 0.5–100 μg NH₃---Nl⁻¹ and (ii) 10–1000 μg NH₃---Nl⁻¹ were linear within ±2%. The detection limit of the method is 0.5 μg TKNl⁻¹. The concentration range of TKN for which the method is suitable is 0.5 μg Nl⁻¹–40 mg Nl⁻¹. The method displayed a high tolerance to interferences from copper, iron, mercury and hardness. Digest procedure gave a high recovery and reproductibility over a wide range of nitrogen compounds tested.     

Effects of sodium and phosphate on growth of cyanobacteria

We conducted laboratory experiments to evaluate the effects of NaCl and phosphorus enrichments on natural phytoplankton assemblages from Lake Michigan in continuous-flow systems, at a dilution rate of 0.25 d⁻¹. The experiment was repeated four times, 1981–1982, using freshly-collected natural lakewater inocula and temperature regimes typical of near-surface waters at initiation (6, 12, 16 and 20°C), at two levels of PO₄−P (1–2 vs 91–92 μg l⁻¹) and of Na⁺ (3–4 vs 9–10 mg l⁻¹) each time. As a single factor, sodium chloride enrichments had no significant effect on growth rates or densities of cyanobacteria in cultures containing natural phytoplankton assemblages from Lake Michigan. However, filamentous cyanobacteria proliferated in the presence of elevated phosphorus concentrations, both with and without concurrent NaCl additions, particularly in warmer waters. Our laboratory results were consistent with the hypothesis that cyanobacteria are favored in phytoplankton of large lakes with low N:P ratios.     

Investigation of the Folin-Ciocalteau phenol reagent for the determination of polyphenolic substances in natural waters

The methodology associated with the Folin-Ciocalteau phenol reagent was investigated and the performance characteristics of a method using sodium carbonate as the supporting medium were determined. Calibration curves using phenol, tannic acid, or l-tyrosine were linear up to at least 1000 μg l⁻¹. The limit of detection was 6 μg phenol l⁻¹ and the relative standard deviation at 100 μg phenol l⁻¹ was 5.2% and at 1000 μg phenol l⁻¹ was 4.1%. The absorbances obtained with equal amounts of a range of potential standards showed variations when compared with that of phenol: phenol (100%), l-tyrosine (62%), oak gall tannin (58%), tannic acid (48%), chestnut tannin (26%), oak tannin (24%), fulvic acid (5%). The method was applicable to a wide range of monohydric and polyhydric phenolic substances and interferences from inorganic and non-phenolic organic compounds were examined. Interference would be expected above 30 μg S²⁻ l⁻¹, 300 μg Mn(II) l⁻¹, or 400 μg SO₃²⁻ l⁻¹. Concentrations of iron >2 mg l⁻¹ as Fe(II) or Fe(III) formed the insoluble iron(III) hydroxide which increased the absorbance, but centrifugation could be used to remove this source of interference. Other potential sources of intereference (e.g. reducing agents and certain metabolic products) would be expected to have a negligible effect in unpolluted waters. Methods using diazotised sulphanilic acid or 4-aminoantipyrine (4-AAP) were found to be inferior when applied to natural water samples.     

Conditions required for the precipitation of aluminium in acidic natural waters

Laboratory and field studies were carried out in order to define the conditions necessary for the precipitation of Al in natural waters of pH 4–6. It is concluded that if precipitation does occur it involves the formation of Al(oxy)hydroxide, not aluminosilicates or basic aluminium sulphates. The solubility product of the Al(oxy)hydroxide is highly temperature dependent (ΔH = −30.5 kcal⁻¹). It is also sensitive to concentrations of SO₄²⁻ and, more markedly, humic substances (HS); both of these decrease solubility, HS by more than an order of magnitude at a concentration of approx. 5 mg l⁻¹ (equivalent to approx. 2.5 mg l⁻¹ dissolved organic carbon). A semi-empirical equation is proposed that allows the prediction of the effective solubility product at different temperatures and at humic concentrations in the range 0–7 mg l⁻¹. Of the 113 natural water samples analysed, only one was calculated to be oversaturated with respect to Al(oxy)hydroxide.     

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.     

Growth responses of selected freshwater algae to trace elements and scrubber ash slurry generated by coal-fired power plants

In laboratory studies, the freshwater algae Ankistrodesmus falcatus, Scenedesmus obliquus, Selenastrum capricornutum, and Microcoleus vaginatus were exposed to potential pollutants from coal-fired power plants, and their growth responses were evaluated. Using a modification of the EPA Algal Assay Procedure Bottle Test, algae were incubated in media containing As(V) as Na₂HAsO₄ · 7H₂O, Cd(II) as CdSO₄, Hg(II) as HgSO₄, Se(VI) as Na₂SeO₄, in solution, and scrubber ash slurry generated at a western U.S. coal-fired power plant complex. First significant inhibition levels as well as algistatic-algicidal levels are reported. The median effective concentration (EC50) values for the potential pollutants ranged from 0.048–30.761 mg l⁻¹ (0.00064–0.41058 M) As(V), 0.005–0.019 mg l⁻¹ (0.00004–0.00017 M) Cd(II), 0.033–0.253 mg l⁻¹ (0.00016–0.00126 M) Hg(II), 0.033–8.511 mg l⁻¹ (0.00042–0.10779 M) Se(VI), and 3.048–15.417% scrubber ash slurry extract (SASE).     

Preliminary studies on the leaching of some trace metals from kitchen faucets

Preliminary studies were carried out on the leaching of copper, zinc, chromium, cadmium and lead from eight kitchen faucets by samples of raw, filtered and distributed Ottawa water, a sample of well water and deionized water containing 2 mg l⁻¹ aqueous fulvic acid. Leaching was effected by allowing the test solutions to stand in the inverted faucets for two successive 24-h periods. Concentrations of the metals found in the leachates were copper: first leaching, 0.12–28.0 mg l⁻¹, second leaching, 0.08-3.54 mg l⁻¹; zinc: first leaching, 0.13-10.25 mg l⁻¹, second leaching, 0.06-2.85 mg l⁻¹; chromium: first leaching, < 1.0 × 10⁻³ − 0.395 mg l⁻¹, second leaching, < 1.0 × 10⁻³−0.032 mg l⁻¹; cadmium: first leaching, < 0.05 × 10⁻³−0.01 mg l⁻¹, second leaching, < 0.05 × 10⁻³−4 × 10⁻³ mg l⁻¹; and lead: first leaching, < 0.2−110.0 mg l⁻¹, second leaching, < 0.2−82.0 mg l⁻¹. The faucets containing lead-soldered copper joints released high concentrations of lead, particularly in the case of leaching with the aqueous fulvic acid solution. Under the conditions of the present investigations it is indicated that in some cases the concentrations of metals leached could lead to intakes in excess of the maximum permissible limits for these metals. However, further investigations will be required to determine the possible contribution of these faucets to metal intake under normal usage.     

Restoration of heavily polluted branches of the Shatt Al-Arab river, Iraq

In view of the desire to improve the water quality of the heavily polluted branches of the Shatt al-Arab River at the City of Basrah, it was proposed to maintain effective flushing as well as contracting sewerage system. The present study was conducted in order to examine the water quality of these branches in an attempt to evaluate the effectiveness of the proposed flushing system. It has been found that their waters contained very low levels of dissolved oxygen and relatively high amounts of both COD and BOD₅. The annual average water quality parameters for Basrah Branches were: dissolved oxygen 3.4 ppm; pH 7.67; hydrogen sulphide 1.4 ppm; ammonia 97 μg-at. N l⁻¹; COD 15.9 mg l⁻¹; BOD₅ 12.7 mg l⁻¹; dissolved silicates 202 μg-at. Si l⁻¹; dissolved reactive phosphate 13.4 μg-at. P-PO₄³⁻ l⁻¹; nitrate 10.4 μg-at. N-NO₃⁻ l⁻¹; nitrite 2.1 μg-at. N-NO₂⁻ l⁻¹ and chlorophyll-α 14.3 mg m⁻³. Based on our calculations, it has been concluded that the proposed system is effective, thus within a flushing cycle all of the above mentioned parameters will become within the acceptable values of the Shatt al-Arab water quality. Moreover, this system has no appreciable effect upon the water quality characteristics of the Shatt al-Arab River due to the fact that it discharges a high volume of water annually. However, It has been recommended to dredge the deposited sludge to a minimum depth of 50 cm.     

The use of uric acid as a method of tracing domestic sewage discharges in riverine, estuarine and coastal water environments

The chemical tracking of sewage effluents discharged into fresh and saline waters presents difficulties, especially in estuaries. The main difficulty is caused by the dissolved constituents being used to monitor the effluent also occurring naturally at similar levels. Uric acid is present at significant levels in untreated sewage and is not normally found in unpolluted waters. Until now no suitable routine method has been available for uric acid estimation in fresh and saline waters at levels normally encountered in the environment. In this paper we describe a recently developed technique using high-performance liquid chromatography which estimates uric acid in both fresh and saline waters in the range 1–10,000 μg l⁻¹ with a precision (2σ) of ±20% at 2 μg l⁻¹, ±4% at 40 μg l⁻¹ and ±2% at 10 mg l⁻¹.     

A modified version of the sodium salicylate method for analysis of wastewater nitrates

The German sodium salicylate method for nitrate determination has been modified and improved by utilizing flocculating effect of the preservative HgCl₂ (1000 mg 1⁻¹). The method gives highly reproducible results in the range of 0·2–16 mg 1⁻¹ nitrate nitrogen and is applicable for routine analysis of untreated sewage. Interfering substances are chloride ions above 1500 mg 1⁻¹ and nitrite ions above 10 mg 1⁻¹N. The yellow color produced by sodium salicylate with nitrate ions obeys Beer's law and remains stable for several hours.     

Nutrient budget for a hypertrophic reservoir

A nutrient budget for the shallow, hypertrophic Ardleigh Reservoir, a pumped storage scheme in eastern England, is described for the period 1979–1982. Algal succession in the reservoir was typical of eutrophic waters, with maximum chlorophyll-a of 98 mg m⁻³. Although the reservoir did not stratify thermally, the concentrations of SRP, Mn and Fe increased in bottom waters during summer. The weight ratio of inorganic N to inorganic P ranged from 720 to 5. On average, SRP represented 72% of the total P content of the reservoir.Some 44% of water input was of pumped river water, 48% being of direct catchment flow. The specific loading of SRP was 5.014 g m⁻² yr⁻¹.Ninety per cent of the annual SRP load was derived from pumped water and 60% of the SRP load was retained in the reservoir. Nitrate input was more diffuse, with approx. 33% from pumped water and 66% from catchment flow. A net release of P from the sediment of 23 mg P m⁻² day⁻¹ was recorded in summer, equivalent to 33% of annual mean external SRP loading. Strategies of P control are discussed in relation to loading models.     

The behaviour of phosphate, nitrate, chloride and hardness in twelve welsh rivers

Selected water quality data from 12 rivers in the area administered by the Welsh Water Authority were analysed for the period 1974–1981. Mean nitrate-nitrogen concentrations varied from 0.4 to 3.7 mg l⁻¹ and were significantly related to the intensity of average catchment run-off; mean orthophosphate-phosphorus concentrations ranged from the limit of analytical detection to 0.730 mg l⁻²; chloride from 11 to 42 mg l⁻¹ and total hardness (as CaCO₃) from 13 to 173 mg l⁻¹. Seasonal patterns of change in concentration were established, generally for all determinands at most sites, but no long-term trends were detected. Relationships between concentration and flow were established for most determinands at many sites, increasing flow generally resulting in decreased concentration. However, positive relationships between nitrate concentration and flow were established at seven sites. Mass flows (kg ha⁻¹ yr⁻¹) were calculated at nine sites only: nitrate-N 4.8–24.6; orthophosphate-P 0.16–3.81; chloride 79–334; total hardness (as CaCO₃) 196–1629. Orthophosphate flows were related to sewered population density, estimates of per capita and land drainage contributions being 1.9 g day⁻¹ and 0.112 kg ha⁻¹ yr⁻¹ respectively.     

The growth inhibition of planktonic algae due to surfactants used in washing agents

A survey of inhibitory effects of nonionic and anionic surfactants, including a soap, used in washing agents, on the growth on three species of freshwater phytoplankton, Selenastrum capricornutum, Nitzschia fonticola and Microcystis aeruginosa was conducted. Based on the specific growth rate, μu estimated from a short period (2 or 3 days) cultivation of test algae, the growth inhibition was determined using EC₅₀ values where μu in the culture medium with surfactant decreased 50% of that without surfactant.The EC₅₀ values of nonionic and anionic surfactants tested here for S. capricornutum ranged from 2 to 50 mg l⁻¹ and from 10 to 100 mg l⁻¹, respectively. The tolerances of three species of algae tested with three surfactants, LAS, AE (EO:9) and soap, were different and the inhibitory effects were species specific. EC₅₀ values of LAS, AE (EO:9) and soap for S. capricornutum were 50–100, 4–8 and 10–50 mg l⁻¹, respectively. Those for N. fonticola were 20–50, 5–10 and 20–50 mg l⁻¹, and those for M. aeruginosa were 10–20, 10–50 and 10–20 mg l⁻¹, respectively.     

Effect of temperature and dissolved oxygen on biodegradation of nitrilotriacetate

The effect of temperature and dissolved oxygen on the rate of biodegradation of nitrilotriacetate (NTA) was examined in water samples collected from the Rur River. Biodegradation of NTA was first order with respect to NTA concentration over a concentration range of 50–1000 μg l⁻¹. First order rate constants showed a typical temperature dependency (temperature coefficient, Q₁₀ = 2) and biodegradation of NTA was observed over a temperature range of 2–24°C. The effect of temperature on the rate of NTA biodegradation was described by the Arrhenius equation, with calculated activation energies in the range reported for ordinary enzyme reactions. Biodegradation of NTA was also observed at low dissolved oxygen concentrations (0.3 mg l⁻¹), although at reduced rates compared to high oxygen concentrations (13 mg l⁻¹). Biodegradation of NTA was oxygen-dependent, suggesting an obligate oxygen requirement for the initial steps in NTA metabolism by natural microbial communities in surface waters. In general, our results indicate that NTA biodegradation will occur in natural waters under conditions of low temperature and low dissolved oxygen and also at low NTA concentrations.     

pH adjustment in anaerobic digestion

In the pH range 6·0–7·5, the pH in anaerobic processes is controlled by the interaction of the carbonic system and a net strong base. The acid-base state of a digestor can be monitored by only measuring pH and CO₂ partial pressure. Shock doses of strong bases and carbonates causes temporary undersaturated CO₂ conditions and excessively high pH. Bicarbonate dosing leaves the CO₂ solubility equilibrium unchanged. In the absence of a CaCO₃ precipitation inhibiting agent. CaCO₃ solubility limits the pH, and Ca(OH)₂ dosing is unable to raise the pH significantly. Orthophosphates inhibit CaCO₃ precipitation. With [PO₄] > 1·0 × 10⁻³mole·1⁻¹. CaCO₃. precipitation is partially inhibited. Ca(OH)₂ dosing being approximately 45 per cent effective for doses up to 15000 mg 1⁻¹ as CaCO₃. At [PO₄] < 1·0 × 10⁻³moles·1⁻¹ orthophosphates eventually precipitate out during Ca(OH)₂ dosing, thus removing the inhibition mechanism: pH is then limited by the CaCO₃ solubility. Most wastes contain [PO₄] > 2·0 × 10⁻³moles·1⁻¹ making pH adjustment with Ca(OH)₂ possible to a pH of about 7·2 although the dosages will be very high. The pH changes in a process following dosing can be predicted by the graphical representation of the carbonic and net strong base systems.     

Denitrification with a bacterial disc unit

An enclosed rotating disc unit was operated anaerobically as a denitrifying system, with methanol as the hydrogen donor. As the bacterial population became established, denitrification rate increased by 1·5 mg NO₃⁻—N reduced m⁻² h⁻², to a maximum rate of 260 mg NO₃⁻—N reduced m⁻²h⁻¹. The C:N ratio necessary for complete denitrification was found to be 2·6:1. Optimum pH for denitrification lay in the range between pH 7·0 and 8·5. Q₁₀ values were 1·38 between 10 and 30°C, −2·66 above 30°C and 13·06 below 10°C.