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.     

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.     

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.     

The methanogenic toxicity and anaerobic degradability of a hydrolyzable tannin

Gallotannic acid was found to be highly toxic to methanogenic activity. Concentrations, representing 50% inhibition, approximated 700 mg l⁻¹. The toxicity was persistent despite the rapid degradation of gallotannic acid to volatile fatty acids and methane. A 72.5% loss of sludge activity was associated with a 1 day exposure of methanogenic granular sludge to 1000 mg l⁻¹ gallotannic acid. The toxicity of gallotannic acid was persistent over 2 month assay periods. The monomeric derivatives of gallotannic acid, gallic acid and pyrogallol were much less toxic. The 50% inhibition concentration of the monomers approximated 3000 mg l⁻¹ and their toxicities were not persistent. No activity losses were evident after sludge was exposed to 3000 mg l⁻¹ gallic acid for 19 days.The lower toxicities of the monomers compared to the gallotannic acid polymer suggests that the mechanism of toxicity was “tanning”, since data in the literature indicate that tannin polymers are more effectively adsorbed and precipitated with proteins compared to their monomeric counterparts. Functional proteins (enzymes) located at accessible sites in or on the methane bacteria are most likely disturbed by the tanning action.     

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.     

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.     

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.     

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.     

Weak and strong acids in the surface waters of the tovdal region in S. Norway

The concentrations of weak and strong acids in surface waters of the Tovdal region of southern Norway were measured during a spring snow-melt period. The determinations were made by the pH titration method due to Gran. The strong acid concentrations in Tovdal river water varied between 3 and 11 μeq 1⁻¹, while the weak acid concentrations were between 62 and 106 μeq 1⁻¹ and the contribution of the weak acids to the hydrogen ion concentration ranged between 10 and 60%. The pH of the river water varied from 4.9 to 5.0 and in the absence of excess strong acid, the weak acids would have produced a pH of 5.2–5.3. The concentration of weak acids and their contribution to the hydrogen ion concentration were least during the period of most rapid thaw.No direct evidence of the nature of the weak acids was obtained, but routine chemical analysis data suggested that inorganic species derived from aluminium and silicon accounted for 40–60 μeq 1⁻¹, while 20–50 μeq 1⁻¹ were attributable to humic and fulvic acids. The titration characteristics of the weak acids could be approximated closely by a polybasic acid with a first ionization constant in the range 10⁻⁶ to 5 × 10⁻⁷ and less well defined weaker ionizations.Measurements on old snow containing coniferous tree litter and on melt water from a rocky barren contained weak acid concentrations comparable to the riverwater, indicating that only slight contact with vegetable matter or the ground is required to obtain significant concentrations of weak acids.     

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.     

An improved determination of chemical oxygen demand in water and wastes by a simplified acid dichromate digestion

A simplified and improved chemical oxygen demand (COD) procedure is suitable for water and waste water samples containing up to 1500 mg Cl l⁻¹. Samples are digested with sulfuric acid, potassium dichromate, silver sulfate, mercury(II) sulfate and sulfamic acid in open glass tubes for 2 h at 140 ± 2°C without boiling, and excess dichromate is determined colorimetrically at 440 nm. The use of 49-position digestion racks, a large oven and a spectrophotometer fitted with a 1-cm flow cell allow analysis of ca. 12 samples h⁻¹. A correction for chloride interference is not required in the 0–500 mg Cl l⁻¹ range. The detection limit is 3 mg l⁻¹, and the relative standard deviation at the 112 mg COD l⁻¹ level is 4.3%. Thirty-five waste water samples were analyzed by the standard dichromate reflux method and by the proposed procedure. There was no significant difference between the two sets of data (P > 0.25). Recovery data for 15 major water pollutants including benzene, toluene and pyridine are presented.     

Hypolimnetic aeration: field test of the empirical sizing method

A hypolimnetic aeration system was recently installed in a small (16 ha S_α) eutrophic lake and a comparison made between measured performance and predicted performance from an empirical sizing method. The design variables used to size the system were: hypolimnetic volume 451,600 m³; maximum hypolimnetic oxygen consumption 0.2 mg l⁻¹ d⁻¹; aerator input rate 2 mg l⁻¹; water velocity 0.76 m s⁻¹ and depth of air release 12.2 m. A 3.7 kW compressor (0.57 m³ min⁻¹) generated a water velocity of 0.46 m s⁻¹, a water flow of 17.7 m³ min⁻¹ and a theoretical hypolimnetic circulation period of 18 days. Dissolved oxygen increased by an average of 1.6 mg l⁻¹ on each cycle through the aerator, and aerator input rates ranged from 0.6 to 2.6 mg l⁻¹. Hypolimnetic oxygen consumption averaged 0.12 mg l⁻¹ d⁻¹ and ranged between 0.02 and 0.21 mg l⁻¹ d⁻¹. The aeration system was unable to meet the daily oxygen demand (90 kg) as the water velocity was slower than expected (0.46 m s⁻¹). To avoid undersizing future aeration installations the following recommendations should be considered when using the empirical sizing formula: (1) estimates of oxygen consumption should be annual maximums from aerobic hypolimnia; (2) aerator input rates should be conservative (e.g. 1–4 mg l⁻¹) and increase with depth; (3) water velocity of 0.45–0.50 m s⁻¹ should initially be used when no information on actual bubble size or velocity is available; (4) aeration start-up should be timed to avoid periods of accumulated oxygen demands.     

The effects of phenol and some alkyl phenolics on batch anaerobic methanogenesis

Phenol and seven alkylphenols (o-, m- and p-cresol, 2.5-, 2.6-, 3.4- and 3,5-dimethylphenol) were added at various concentrations to aliquots of domestic anaerobic sludge in Hungate serum bottles and these were incubated at 37°C. The concentration of methane in the headspace gas was monitored to determine if the phenolics were fermented to methane or if they inhibited the anaerobic process. Only phenol and p-cresol were fermented to methane. At 500 mg l⁻¹ (but not at 300 mg l⁻¹) 2,5-, 3,4- and 3,5-dimethylphenol reduced the rate and the amount of methane produced. The cresols were inhibitory at 1000 mg l⁻¹ but not at 400 mg l⁻¹.In cultures supplemented with acetate and propionate (VOA), and in unsupplemented cultures, phenol at concentrations up to 500 mg l⁻¹ was fermented to methane. Between 800 and 1200 mg l⁻¹ phenol, methane production was neither enhanced nor inhibited relative to control cultures containing no phenol. Inhibition of methane production was evident when phenol was present at 2000 mg l⁻¹. Thus the methanogens are less susceptible to phenol inhibition than are the phenol-degrading acid formers. In similar experiments with p-cresol: enhanced methane production was observed at concentrations of 400 mg l⁻¹; no enhancement or inhibition was observed at 600 mg l⁻¹; and inhibition was noted when p-cresol was present at 1000 mg l⁻¹.     

Acute and chronic toxicity of copper to the fathead minnow in a surface water of variable quality

Acute and chronic toxicity tests conducted with the fathead minnow and copper used as the source of dilution water a natural stream to which a sewage treatment plant upstream contributed a variety of materials known to affect acute copper toxicity. Nominal total copper 96-h median tolerance limit values (96-h TL50), determined with static testing procedures, ranged from 1.6 to 21 mg l⁻¹. Dissolved copper 96-h TL50 values ranged from 0.60 to 0.98 mg l⁻¹. The maximum acceptable toxicant concentration (MATC) based on survival, growth, reproduction, and hatchability of eggs was between 0.066 and 0.118 mg l⁻¹.     

The toxicity of various mining flotation reagents to rainbow trout (Salmo gairdneri)

Preliminary testing of eight collectors (xanthates) and four frothers in 96-h static and 28-day flow-through bioassays using rainbow trout as the test organism show a great disparity in the toxicity of the chemicals administered in these two ways.For the short-term tests, the relative toxicity of the compounds is expressed as an lc₅₀ or as a range of concentration in mg l⁻¹ in which the lc₅₀ is expected to fall. Of the collectors tested in this way sodium ethyl and potassium amyl xanthate were the most toxic, with lc₅₀'s in the range of 30–50 mg l⁻¹. Among the frothers, xylenol (cresylic acid) was found to be the most toxic (5.6 mg l⁻¹ >lc₅₀ > 3.2 mg l⁻¹) while polypropylene glycol was least toxic (lc₅₀ > 1000 mg l⁻¹).The long-term tests using potassium ethyl, sodium isopropyl, sodium ethyl, and potassium amyl xanthate indicated that in the flow-through system, the toxicity of the chemicals was in the order of 100 fold greater compared with the static bioassay results.     

Acute and chronic toxicity of lead to rainbow trout salmo gairdneri, in hard and soft water

Lead was found to be highly toxic to rainbow trout in both hard water (hardness 353 mg l⁻¹ as CaCO₃) and soft water (hardness 28 mg l⁻¹. Analytical results differ greatly with methods of analysis when measuring concentrations of lead in the two types of water. This is exemplified in LC50's and maximum acceptable toxicant concentrations (MATC's) obtained when reported as dissolved lead vs total lead added in hard water. Two static bioassays in hard water gave 96-h LC50's of 1.32 and 1.47 mg l⁻¹ dissolved lead vs total lead LC50's of 542 and 471 mg l⁻¹, respectively. In a flow-through bioassay in soft water a 96-h LC50 of 1.17 mg l⁻¹, expressed as either dissolved or total lead, was obtained. From chronic bioassays, MATC's of lead for rainbow trout in hard water were between 18.2 and 31.7 μg l⁻¹ dissolved lead vs 120–360 μg l⁻¹ total lead. In soft water, where exposure to lead was initiated at the eyed egg stage of development, the MATC was between 4.1 and 7.6 μg l⁻¹. With exposure to lead beginning after hatching and swim-up of fry, the MATC was between 7.2 and 14.6 μg l⁻¹. Therefore, fish were more sensitive to the effects of lead when exposed as eggs.     

High-rate overland flow

Recommended loading rates for treating raw domestic wastewater by overland flow are 6.3–15 cm wk⁻¹. Information provided in the literature yields little insight regarding the upper range of hydraulic loading rates that could be effectively treated by overland flow. Therefore, field investigations were conducted to evaluate the performance of the overland flow system at overland flow rates from 0.95 m³ day⁻¹ m⁻¹ width of slope (13 cm wk⁻¹ to 4.15 m³ day⁻¹ m⁻¹ (57 cm wk⁻¹).Preliminary treated municipal wastewater was pumped to overland flow slopes, each approx. 3.7 m wide and 36.5 m long. The slope of each plot was 2.5%. The cover crop consisted of a mixture of ryegrass, bluegrass and fescue grass. The plots were operated for 2 years at six different hydraulic loading rates.Effluent BOD₅ concentration averages varied from 6 to 11 mg l⁻¹. The reduction of influent BOD₅ concentration ranged from 87 to 93%. Mean effluent suspended solids values were from 6 to 9 mg l⁻¹ with reductions of influent concentrations of 91–95%. Hydraulic application rate had little effect on percent BOD₅ or suspended solids removal.Total phosphorus reductions were minimal at all hydraulic application rates due to limited soil water contact.Ammonia concentration in the effluent ranged from 1 mg l⁻¹ NH₃-N at the 0.95 m³ day⁻¹ m⁻¹ (13 cm wk⁻¹) applied flow rate of 11.7 mg l⁻¹ NH₃-N at the 4.15 m³ day⁻¹ m⁻¹ (57 cm wk⁻¹) loading rate. Ammonia and nitrogen reductions decreased as the applied flow rate increased. Consequently, lower overland flow rates are necessary for nitrogen removal.The use of high-rate overland flow could potentially reduce the land necessary for this form of land application, if nutrient removal was not a local concern.     

The acute toxicity of vanadium and copper to eyed eggs of rainbow trout (Salmo gairdneri)

The effects of vanadium (25–595 mg l⁻¹) and of copper (0.03–4.78 mg l⁻¹) on embryonic survival and hatching of eyed eggs of rainbow trout, Salmo gairdneri, were investigated. Copper was approx. 300-fold more toxic than vanadium (96-h LC₅₀ = 0.4 and 118 mg l⁻¹, respectively) but had little effect on the timing of hatch. Vanadium induced premature hatching of eyed eggs at concentrations from 44 to 595 mg l⁻¹. Concentrations of copper required to produce lethality in eyed eggs were similar to concentrations required to produce mortality in juveniles. Vanadium concentrations approx. 15 times higher were required to produce mortality in eyed eggs than in juveniles. Therefore, acute exposure of eyed rainbow trout eggs to vanadium is not a sensitive toxicity test for use in establishing water quality criteria or maximum acceptable toxicant concentrations.     

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.