The role of pH on the acute toxicity of sulfite in water

The toxicity of sulfite to fish decreases with increasing pH value, because the HSO⁻₃ ion is more toxic than the SO²⁻₃ ion. An effective sulfite concentration S_eff which is proportional to the toxicity on fish, is expressed by the following equation: S_eff=[HSO⁻₃]+ƒ[SO²⁻₃]where ƒ is a coefficient which expresses the change of toxicity of sulfite depending on the pH of the water, and varies for each species of fish. For goldfish, owing to the very small toxic contribution of SO²⁻₃ ion (ƒ = 0·07), the pH dependence of the toxicity of sulfite on pH was so strong that sulfite seemed almost non-toxic in basic solution. However, ƒ for guppy is somewhat larger (ƒ = 0·20) so that the toxicity of sulfite weakly depends on the pH value of water.     

A pilot-plant scale evaluation of potential precipitants in the secondary precipitation process

Chemical precipitation of presettled domestic wastewater (secondary precipitation) was studied in three pilot-plants operating in parallel with alum, ferric iron and lime as precipitants. With all precipitants phosphates were effectively removed down to less than 0·1 mg P l⁻¹. Total phosphorus removals were closely connected to the settling properties of the flocs. The factor that seemed to influence settling properties most was pH. In a favourable pH-range it was possible to achieve total phosphorus concentrations in the effluent of less than 0·5 mg P l⁻¹. The COD removal was at an average 70, 60 and 55% with alum, ferric iron and lime as precipitants.     

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.     

Ozonation of water containing chlorine or chloramines. Reaction products and kinetics

Ozone reacts with free aqueous chlorine when present as hypochlorite ion (OCl⁻) with a second order rate constant of 120 ± 15 M⁻¹ s⁻¹ at 20°C. About 77% of the chlorine reacts to produce Cl⁻ and 23% is oxidized to ClO⁻₃. No ClO⁻₄ is formed. Conversion of chlorine to monochloramine reduces the ozone reaction rate to 26 ± 4 M⁻¹ s⁻¹, independent of pH, NH₂Cl is transformed quantitatively to NO⁻₃ and Cl⁻ by O₃. Rate data for other chloramines are also presented. The direct reaction of ozone with chlorine accounts for a significant amount of the chlorine and ozone demand found when the two oxidants are used in combination under water works conditions.     

Study on chlorine disinfection of pond effluent

Chlorine disinfection experiments were conducted to investigate the die-off patterns of the fecal coliforms when present in waste stabilization pond effluents containing from 100 to 400 mg l⁻¹ algae. The fecal coliform inactivation was observed to occur at two rates, i.e. an initial rapid kill followed by a slower kill. The magnitude of inactivation was found to be proportional to the initial chlorine dose and contact time and inversely proportional to the algal concentration. A mathematical model was developed to predict the fecal coliform survival ratio during the chlorination of the pond effluent. When compared with the experimental data, the predicted results had a correlation coefficient of 0.981.     

Field studies on coliphages and coliforms as indicators of airborne animal viral contamination from wastewater treatment facilities

The occurrence of animal viruses in the aerosol emissions of wastewater treatment facilities was evaluated by direct assay and by the use of coliforms and coliphages as indicator organisms. Coliforms and coliphages were compared and evaluated with regard to their suitability as indicators of airborne animal viral contamination from wastewater treatment facilities. Two plants, one with treatment by activated sludge and the other by trickling filtration, were studied. Field air sampling procedures used large-volume air samplers, with recirculation devices, and Andersen samplers. Airborne viruses were enumerated by a most probable number (MPN) procedure. Partially treated liquid sewage contained about 1.0 × 10² pfu l⁻¹ of animal viruses assayed on Buffalo Green Monkey (BGM) cells, 3.6 × 10⁵ and 5.0 × 10⁵ pfu l⁻¹ of coliphages, depending upon the E. coli host strain used for assay, and 2.0 × 10⁹ colonies l⁻¹ of coliform bacteria. No airborne animal viruses were recovered, airborne coliphage levels averaged 2.3 × 10⁻¹ and 3.0 × 10⁻¹ MPN m⁻³, coliforms from aerosol emissions were 2.1 × 10² colonies m⁻³. Ratios of coliphages to animal viruses indicate that wastewater treatment plants may be continuous sources of low level concentrations of animal virus aerosols. Evidence shows coliforms to be much less stable than coliphages in the airborne state. Coliphages may be a more acceptable indicator of airborne animal viral contamination than coliforms.     

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.     

The Fe3O4-formation by the ‘Ferrite Process’: Oxidation of the reactive Fe(OH)2 suspension induced by sucrose

A mechanism of the formation of small particles of iron oxide in the wastewater treatment system ‘Ferrite Process’ is described. Small particles consisting of the Fe₃O₄−γ-Fe₂O₃ solid solution having slightly higher content of γ-Fe₂O₃ were obtained by the aerial oxidation of Fe(OH)₂ suspension in the presence of a weak dispersing reagent, sucrose, at pH 9.0. The increase of γ-Fe₂O₃ content is caused by a further oxidation of the Fe₃O₄ particles in the course of the reaction. The further oxidation was accelerated below 1000 Å of the particle size. When SO²⁻₄ ion coexisted with sucrose in the reaction medium, the further oxidation was reduced and the treatment of the wastewater was improved. At a temperature interval of 40°–65°C, the formation of α-FeOOH was completely inhibited by a small amount of sucrose and only Fe₃O₄ was obtained.     

Microbiological effects of wastewater effluent discharge into coastal waters of Puerto Rico

Microbiological effects of non-disinfected, combined chemical and domestic wastewater effluent discharge into coastal waters north of Barceloneta. Puerto Rico were investigated by membrane filter enumeration of fecal indicator bacteria and by enrichment isolation of specific pathogens. A wastewater plume was detected and delineated around the sewage outfall, located 800 m offshore and 30 m below the ocean surface. Fecal coliform and fecal streptococcus counts within the plume were significantly (F test) larger than comparable counts outside the plume. The shape and location of the plume was compatible with current patterns and prevailing winds and extended as far as 3.7 km west of the outfall, at which point the fecal coliform count was 146 100 ml⁻¹. The average non-plume fecal coliform concentration was 6.7 100 ml⁻¹. Specific pathogens isolated included Salmonella and Vibrio spp, including V. cholerae non-01 serovar isolated from a nearby river also impacted by the sewage plant.     

Treatment of low strength domestic wastewater using the anaerobic filter

A laboratory scale anaerobic filter packed with synthetic high surface area trickling filter media was used to treat a low strength domestic wastewater averaging 288 mg 1⁻¹ COD. The filter was operated for 60 days after reaching steady-state at 20, 25, 35°C at a loading rate of 0.02 lb COD ft⁻³ day⁻¹ and 24 h hydraulic retention time. Filter effluent BOD₅ averaged 38 mg 1⁻¹ providing an average removal rate of 79%, and effluent COD averaged 78 mg 1⁻¹, corresponding to a 73% removal rate. Removal efficiencies showed very little sensitivity to daily fluctuations in influent wastewater quality. The filter performance at 25 and 35°C was not significantly different, but BOD and TSS removal efficiency declined a: 20°C. Gas production averaged 0.027 ft⁻³ of gas per ft³ of influent wastewater, or 1.875 ft³ of gas per pound of influent COD. Gas composition averaged 30% nitrogen, 65% methane, and 5% carbon dioxide. Ammonia nitrogen and sulfides both increased during treatment. It is concluded that the anaerobic filter is a promising candidate for treatment of low strength wastewaters and that post treatment for sulfides and ammonia may be necessary.     

Resistance transfer fecal coliforms isolated from the whippany river

Three sites on the Whippany River, a tributary of the Passaic Watershed in Morris County, N.J., were monitored for resistance transfer coliforms. A high percentage of fecal coliform isolates showed multiple antibiotic resistance. A significant number of lac⁻ and lac⁻ isolates proved to be donors of transmissible antibiotic resistance plasmids (R donors), by conjugation with a recipient strain of Salmonella gallinarum. Re-examination of testing methods used for recreational and potable water sources is suggested by these findings.     

Études des transformations des formes du carbone, azote, phosphore, soufre et des principaux éléments minéraux au cours de la mesure de la demande totale en oxygene—III transformation des formes du soufre

Previous experiments carried out with the laboratory TOD meter Ionics 225 of the DOW Chèmical made it possible (after a high temperature catalytic action) to characterize the stable forms of organic and inorganic carbon and nitrogen (NH₄⁺, NO₂⁻, NO₃⁻), and the principal cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) in the course of the total oxygen demand (TOD) measurement.The object of this study is firstly to compare the oxidation capability of different techniques of organic pollution (particularly the COD and TOD) in relation to the constituent elements of the organic matter C, N, P, S, and to calculate the possible interferences of the inorganic compounds at the time of TOD test.These investigations warrant the application of this technique to measure the amount of organic pollution in relatively mineralized conditions (Industrial wastewater, sea-water…). The present publication is concerned more with the study of the transformation of the organic and inorganic sulphur forms (S²⁻, SO₃²⁻. SO₄²⁻) in the course of the TOD measurement.The study of the oxidizability of the organic sulphur compound type C_xH_yO_zS, made it possible to establish a specific relation with a ratio of 0–50 mg of organic sulphur l⁻¹, between the oxygen demand of this element [TOD (S)] and its concentration (TOD (S) = 0.97 [S]).These tests showed a partial oxidation of the sulphur to SO₂ and SO₃ as the literature claimed. On the other hand, the oxidation of the same compounds during the COD tests varies greatly and although it is not possible to establish a correlation between these two measurements, as applies in the case of organic nitrogen, nevertheless these experiments showed a greater reliability of the TOD compared with the COD in the oxidation of organic matter in general. We then carried out experiments on the different mineral forms of sulphur in order to distinguish the possible effects and to recommend simple improvements.A relative study on sulphate ions had been carried out with standard solutions which have the same TOD (the basic TOD is obtained using potassium phthalate acid) and the same increasing concentration of the salt M₂SO₄ type. The experiments showed that the basic TOD decreases when the concentration of sulphate ions is increased (Fig. 3). Therefore, the interference is negative and taking into consideration the specific oxygen demand of the cation, we can propose an evaluation of this interference (ΔTOD (SO₄²⁻) = 0.203 [SO₄²⁻]). The same experiments have been conducted with a salt of M₂SO₃ type and similar results obtained (Fig. 5).The specific interference of the sulphite ion is negative and can be estimated by the following equation (ΔTOD (SO₃²⁻) = 0.132 [SO₃²⁻]). In both cases, we have to note that the transformation of these inorganic anions occurs between those relative to the theoretical dissociation reaction corresponding to the appearance of the oxide SO₂ and SO₃. For sulphurous on the contrary, the interference is positive and therefore corresponds to an extra oxygen demand (Fig. 8).The experiments were conducted directly with the M₂S salts (M representing K or Na) in aqueous solution.The evaluation of this interference had been made in the consideration of two concentration ranges of the sulphurous ions (0–35 mg S²⁻ l⁻¹): TOD (S²⁻) = 0.4 [S²⁻] and (35–100 mg S²⁻ l⁻¹): TOD (S²⁻) = 1.2 [S²⁻] − 30.Therefore this study confirms a better oxidation of the organic matter by TOD test in comparison with COD test.But sulphate and sulfite have a negative interference in the TOD measurement, whereas sulphurous is positive.The evaluation model of these interferences allows a correction to be made of the TOD value or to verify TOD measurement of organic pollution obtained by this technique.     

Ozone oxidation of pharmaceuticals, endocrine disruptors and pesticides during drinking water treatment

This study investigates the oxidation of pharmaceuticals, endocrine disrupting compounds and pesticides during ozonation applied in drinking water treatment. In the first step, second-order rate constants for the reactions of selected compounds with molecular ozone (k_O3) were determined in bench-scale experiments at pH 8.10: caffeine (650 ± 22 M⁻¹ s⁻¹), progesterone (601 ± 9 M⁻¹ s⁻¹), medroxyprogesterone (558 ± 9 M⁻¹ s⁻¹), norethindrone (2215 ± 76 M⁻¹ s⁻¹) and levonorgestrel (1427 ± 62 M⁻¹ s⁻¹). Compared to phenolic estrogens (estrone, 17β-estradiol, estriol and 17α-ethinylestradiol), the selected progestogen endocrine disruptors reacted far slower with ozone. In the second part of the study, bench-scale experiments were conducted with surface waters spiked with 16 target compounds to assess their oxidative removal using ozone and determine if bench-scale results would accurately predict full-scale removal data. Overall, the data provided evidence that ozone is effective for removing trace organic contaminants from water with ozone doses typically applied in drinking water treatment. Ozonation removed over 80% of caffeine, pharmaceuticals and endocrine disruptors within the CT value of about 2 mg min L⁻¹. As expected, pesticides were found to be the most recalcitrant compounds to oxidize. Caffeine can be used as an indicator compound to gauge the efficacy of ozone treatment.     

Distribution of halomethanes in potable waters of Kuwait

The distribution of bromine containing trihalomethanes in the water distribution system of Kuwait has been studied. Total halomethanes in the drinking water averaged 25.6 ± 9.1 μg l⁻¹ with a maximum of 50.5 μg l⁻¹. Average concentrations (μg l⁻¹) of individual compounds were: CHBr₃, 13.6 ± 4.6; CHBr₂Cl, 8.8 ± 3.7; CHCl₂Br, 3.3 ± 1.5. Water from roof top storage tanks contained significantly less halomethanes than that from underground reservoirs.     

Enhanced uptake of phosphorus by activated sludge-effect of substrate addition

Studies were undertaken to examine the effect of substrate addition upon the release and subsequent uptake of phosphorous by a biological wastewater treatment laboratory scale system.A train of six reactors were fed at a rate of 16 ml min⁻¹ raw wastewater using a sludge recycle ratio of 0.75 (12 ml min⁻¹). The first two reactors were simply stirred (anoxic) without the addition of air and the remaining four were aerated with excess air.Various substrates were added to the first reactor (anoxic) at different concentrations. It was determined that all the short chain substrates tested enhanced the release of phosphorus in the anoxic stages and subsequently led to increased biological uptake (removal) of phosphorus. The substrates tested included sodium acetate, acetic acid, butyric acid, ethanol and methanol.It was determined that 30 mg l⁻¹ sodium acetate was the optimum dose for biological release and uptake of phosphorus and the addition of any greater concentration had marginal effect on the ultimate removal of phosphorus.The effect of these substrates showed some specificity regarding phosphorus release, with butyric acid causing the greatest release and sodium acetate the least. However as far as phosphorus uptake (removal) was concerned, this phenomenon of substrate-specificity was less significant. For all substrates, effluent phosphorus concentration was within ± 1 mg l⁻¹ with an approximate mean concentration of 1 mg l⁻¹ residual.Phosphorus released (approx. 14 mg l⁻¹) at higher temperature (29°C) was 75% greater than at the lower temperature (24°C). Similarly the final residual phosphorus at 29°C was 33% lower than at 24°C.     

Water quality criteria for European freshwater fish: Report on ammonia and inland fisheries

In establishing water quality criteria for European inland fisheries, the effect of ammonia is an important factor to be considered. Sewage effluent, effluents from certain industries and from agriculture are common sources of ammonia in water.The harmful effects of ammonia on fish are related to the pH value and the temperature of the water due to the fact that only the un-ionized fraction of ammonia is poisonous. The un-ionized fraction increases with rising pH value, and with rising temperature.Fish differ slightly in their tolerance to ammonia depending on species. The difference in tolerance being more significant for short periods of exposure. The difference in tolerance is, however, not great enough to justify different criteria for different species.The lowest toxic concentration found for salmonids is 0·2 mg NH₃ 1⁻¹ (un-ionized), but other adverse effects caused by prolonged exposure are only absent at concentrations lower than 0·025 mg NH₃ 1⁻¹ (un-ionized). Concentrations of total ammonia which contain this amount of un-ionized ammonia vary from 19·6 mg 1⁻¹ (pH 7·0, 5°C) to 0·12 mg 1⁻¹ (pH 8·5, 30°C).The criterion should not be applied to temperatures below 5°C or to pH values above 8·5 when other factors have to be taken into consideration.     

A quantitative investigation of the reaction of ozone with p-toluenesulfonic acid in aqueous solution as a model compound for anionic detergents

The reaction of ozone with p-toluenesulfonic acid (PTA) at initial pH 3 and 12 in aqueous solutions (25°C) has been studied at initial concentration 1 mmol l⁻¹ and ozone dose is 24 mg min⁻¹ 1. and 11 mg min⁻¹ 1. respectively. The substrate elimination follow a zero order rate law. A 98% p-toluenesulfonic acid reduction requires at least 7 mol O₃ per mol PTA, however to remove 100% PTA the consumption of ozone increases to 16 mmol O₃ per mmol PTA. At this point a 28% reduction of DOC and a 74% COD reduction was achieved.The PTA decomposition is quicker at higher ozone flow rate, but the specific ozone consumption increases also. As oxidation products the following compounds were identified and their quantitative variations as function of ozonation time were measured: methylglyoxal, acetic acid, formic acid, pyruvic acid, oxalic acid, H₂SO₄ and H₂O₂. As byproduct mesoxalic acid was identified. At pH 12 lactic acid as a further oxidation product was observed.Balances of carbon, sulfur and methyl as well of the acid equivalents indicate one or more intermediates with a sulfonic acid group. These intermediates with a proportion of about 20% disappear after 100% PTA elimination. On account of these results a reaction mechanism is discussed.     

Determination of phosphate in wastewaters by ion-exclusion chromatography with flow coulometric detection

Ion-exclusion chromatography of PO₄³⁻ in wastewaters has been investigated on a cation exchange resin in the H⁺-form. Phosphate ion was chromatographed by ion-exclusion as H₃PO₄ formed by cation exchange, and monitored with a flow coulometric detector based on the electrochemical reaction of H⁺ ion from H₃PO₄ and p-benzoquinone at a constant applied potential (+0.45 V vs Ag-AgI) or a conductometric detector. A reasonable separation of PO₄³ from strong acid anions (Cl⁻ SO₄²⁻ and NO₃⁻) and CO₃²⁻ as coexisting anions could be accomplished by isocratic elution with 60% (v/v) acetone-water. The calibration graph for PO₄³⁻ with the flow coulometric detector was linear over the concentration range 1–150 ppm (slope = 0.982), but not with the conductometric detector. The agreement of the analytical results of PO₄³⁻ between the ion-exclusion chromatography with the flow coulometric detector and the colorimetry (molybdenum-blue method) was excellent for some industrial wastewater and domestic sewage samples.     

A mercury-free accelerated method for determining the chemical oxygen demand of large numbers of water samples by autoclaving them under pressure with acid-dichromate

In order to fulfill the objective of a water control program based on frequent sampling in several wastewater treatment plants, rivers and lakes a simplified method for measuring COD was developed. The procedure, in this article called the RR-method, includes: small sample and reagent volume; rapid addition of a mixture of all reagents to the sample; exclusion of mercury; autoclaving at 120°C for 1 h in flasks with fitted glass stoppers. To avoid dilution before analysis the method has been adapted for wastewater (I: 10–300 mg O₂ l⁻¹) and fresh water (II: 10–100 mg O₂ l⁻¹).Parallel analyses on different types of water samples according to Standard Methods showed that the yield by the RR-method was about 10% lower (Table 2). With water from the wastewater treatment plant at Uppsala (COD around 20 mg O₂ l⁻¹), the two methods gave an identical result. The somewhat lower yield was mostly due to decreased dichromate concentration and oxidation temperature. The lower oxidation potential made correction for chloride interference unnecessary below 1 g Cl⁻ l⁻¹ (Table 1).The RR-method also showed a good correlation to the values for KMnO₄-consumption. Parallel analyses of 318 samples from 14 wastewater receiving lakes gave the correlation coefficient r = +0.90 (Fig. 1).