Role of aquatic plants in wastewater treatment by artificial wetlands

This report describes investigations using artificial wetlands which quantitatively assess the role of each of three higher aquatic plant types, Scirpus validus (bulrush), Phragmites communis (common reed) and Typha latifola (cattail), in the removal of nitrogen (via sequential nitrification-denitrification), BOD and TSS from primary municipal wastewaters. During the period August 1983–December 1984, the mean ammonia concentration of 24.7 mg l⁻¹ in the primary wastewater inflow (hydraulic application rate = 4.7 cm day⁻¹) was reduced to mean effluent levels of 1.4 mg l⁻¹ for the bulrush bed, 5.3 mg l⁻¹ for the reed bed and 17.7 mg l⁻¹ for the cattail bed, as compared to a mean value of 22.1 mg l⁻¹ for the unvegetated (control) bed. For all three vegetated beds, the mean effluent ammonia values were significantly below that for the unvegetated bed and for the inflow. The bulrushes and reeds (in that order) proved to be superior at removing ammonia, both with mean effluent levels significantly below that for the cattail bed. The high ammonia-N (and total N) removal efficiencies shown by the bulrush and reed beds are attributed to the ability of these plants to translocate O₂ from the shoots to the roots. The oxidized rhizosphere so formed stimulates sequential nitrification-denitrification. Similarly BOD removal efficiencies were highest in the bulrush and reed beds, both with mean effluent BOD levels (5.3 and 22.2 mg l⁻¹, respectively) significantly below that for the unvegetated bed (36.4 mg l⁻¹) and equal to or better than secondary treatment quality (30 mg l⁻¹). Our results demonstrate that higher aquatic plants can indeed play a significant role in secondary and advanced (N removal) wastewater treatment by wetland systems, a role that is completely distinct from that associated with their pollutant uptake capacity.     

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.     

Factors affecting nutrient loads in some Iowa streams

The export and concentration of inorganic nitrogen and total phosphorus from 34 watersheds in a northwestern Iowa lake district were measured during March 1971–August 1973. Annual nutrient losses were approximately 0.35 kg ha⁻¹ P. 6.7 kg ha⁻¹ NO₃-N, and 1.0 kg ha⁻¹ NH₃-N. A statistical analysis of the relationship between land-use and plant nutrients was used to determine differences among streams. Animal units in feedlots were significantly correlated with phosphorus and ammonia nitrogen (mg l⁻¹ and kg ha⁻¹ yr⁻¹). Nitrate nitrogen was negatively correlated with the percentage of watershed in marshland. Tile drainage and surface runoff from grasslands, feedlots, cornfields, and soybean fields were analyzed for nitrogen and phosphorus in spring 1974: mean values are given.     

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.     

Liquid/suspended solid phase partitioning of polycyclic aromatic hydrocarbons in coal coking wastewaters

Wastewater samples were collected from five streams among two coke plants and characterized by high pressure liquid chromatography and gas chromatographic mass spectrometry. Wastewater streams included the ammonia still influent, ammonia still effluent and biological oxidation effluent. Samples collected from these streams were separated into liquid and suspended solid phases and each phase was analyzed for eleven polycyclic aromatic hydrocarbons (PAH). Total wastewater concentrations for these compounds ranged from about 2000 μg l⁻¹ in the ammonia still influent to 5–120 μg l⁻¹ in the biological oxidation effluent. Wastewater PAH were partitioned between liquid and suspended solid phases, and in most samples suspended solid phase PAH accounted for approx. 80% or more of total wastewater PAH. Partitioning in the biological oxidation effluent stream was correlated with aqueous solubility and n-octanol/water partition coefficients. Wastewater treatment consisting of sedimentation, ammonia stripping, and biological oxidation generally reduced liquid phase PAH concentrations to the range of 1 μg l⁻¹ or less. Effective removal of wastewater suspended solids will reduce total effluent PAH concentrations, hence there is need to address issues regarding removal of residual wastewater suspended material including characterization of the distribution of PAH with respect to suspended particle size.     

The treatment of leachates from domestic wastes in landfills—I: Aerobic biological treatment of a medium-strength leachate

A medium-strength leachate from domestic solid wastes in a landfill (COD 5000 mg l⁻¹, BOD 3000 mg l⁻¹ was treated using aerobic biological processes in continuous-flow, laboratory-scale reactors at low temperatures. Each unit was completely mixed, and mixed liquor was wasted such that solids retention time (SRT) was equal to the hydraulic retention period.At 10 C with addition of phosphate (COD:P less than 100:1) SRT values of 10 days were required to obtained well-clarified effluents, and high removal of BOD (>;98%) and COD (>;92%). Reduction of temperature to 5°C resulted in adverse effects on settling of sludges from units with SRT values of less than 10 days, but in other units good removal of organic materials could still be obtained. These units operated successfully with concentrations of mixed liquor volatile suspended solids (MLVSS) of 1450 mg l⁻¹, equivalent to a ratio of F/M of 0.21 kg BOD kg⁻¹ MLVSS day⁻¹ or less. Removal of ammoniacal nitrogen which took place (influent concentration 80 mg l⁻¹ as N) resulted from incorporation in biomass, and at SRT values of 10 days no nitrification took place at 5 or 10 C. Higher concentrations of ammonia in influent leachates resulted in ammonia in effluents when the ratio of BOD:N was less than about 100:3.6. Increasing the SRT of units to 20 days resulted in erratic conversion to nitrite, but reduced pH-values and possible simultaneous denitrification caused floating sludges and poorly-clarified effluents. Removal of ammonia is identified as a major problem when treating leachates, and further research is recommended.     

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).     

Long-term effects of treated domestic wastewater on brown trout

A 12-month bioassay was conducted to determine the effects of unchlorinated, treated, domestic wastewater on survival, growth, swimming performance, and gill tissue of brown trout (Salmo trutta). Ammonia was the toxicant of concern, because the facility's effluent periodically exceeded the U.S. Environmental Protection Agency's (EPA) recommended criterion. Juvenile brown trout (initial weight = 2 g), which were exposed to six concentrations (0–37%) of effluent, were fed a restricted ration, so that growth rates were similar to those of wild stream residents. At the highest effluent concentration, monthly mean concentrations of un-ionized ammonia ranged from 0.004 to 0.055 mg l⁻¹ NH₃---N (at. wt = 14); these concentrations exceeded the EPA criterion of 0.016 mg l⁻¹ about 40% of the time. There were no significant effects of effluent concentration on survival, growth, or swimming performance of brown trout, but the degree of damage to gills was directly related to effluent concentration.     

Investigations on natural Hungarian zeolite for ammonia removal

Use of natural zeolites deposited at Tokaj mountain, Hungary, for ammonia removal from synthetic and municipal wastewaters was studied. The optimal ion exchange conditions found were as follows: Na-form clinoptilolite, 0.5–1.0 mm in particle size and about 5–7 BV h⁻¹ loading rate. Using synthetic wastewater in the column of 9.5 cm i.d. × 92 cm, about 4.50 mg NH₃-N g⁻¹ clinoptilolite ammonia breakthrough capacity was achieved. For regeneration of the ion exchange bed, 10–20 BV of regenerant were necessary to remove the 98–99%, of ammonia with flow rate of a 5–7 BV h⁻¹.     

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.     

Effect of surfactants on the determination of sulphate in waters

The effects of pure cationic, anionic and non-ionic detergents, industrially prepared detergents, sodium tripolyphosphate, sodium pyrophosphate, soap and NTA, in quantities up to 1000 mg l⁻¹, on the analysis of soluble iron in water using the phenanthroline, tripyridine and biquinoline methods were investigated. The tripyridine method is superior to the other two methods for the determination of iron in the presence of up to 1000 mg l⁻¹ of various surfactants but not for up to 100 mg l⁻¹ of non-ionic detergents. The phenanthroline method can be used to determine iron in the presence of up to 1000 mg l⁻¹ of cationic, anionic and non-ionic detergents, but sodium tripolyphosphate interfered above 2 mg l⁻¹. The biquinoline method can be used for the determination of iron in the presence of up to 1000 mg l⁻¹ of cationic, 100 mg l⁻¹ of anionic and 70 mg l⁻¹ of non-ionic detergents, and 50 mg l⁻¹ of sodium tripolyphosphate.     

The chronic effects of fluoride on the estuarine amphipods Grandidierella lutosa and G. lignorum

The toxicity of fluoride in the estuarine environment was tested, using a mixed culture of the estuarine amphipods Grandidierella lutosa and G. lignorum in life-cycle bioassays. Toxin was dosed in a continuous (intermittent) flow system using a proportional dilution doser. The tests ranged in duration from 39 to 90 days, spanning between 1 and 4 generations in that time. The tests were conducted in sea-water at temperatures of 23–25°C. Background sea-water levels during the experiments fluctuated between 1.3 and 1.7 mg l^−t F′. Improved population increases were detected in fluoride levels slightly above background. Maximum amphipod population increase was measured during three 90-day multi-generation experiments, at a mean fluoride level of 2.64 mg l⁻¹. Population performance returned to levels comparable to control at a mean for the 3 experiments of 5.0 mg l⁻¹ F′. Maximum acceptable toxicant concentration (MATC) was therefore, by definition, set at 5.0–6.2 mg l⁻¹ F′ (mean calculated for three 90-day experiments). Data on female fecundity suggested that the MATC might even be slightly lower, with a mean MATC of 4.15 mg l⁻¹ F′.     

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.     

Azolla–Anabaena's behaviour in urban wastewater and artificial media – Influence of combined nitrogen

The results of using the nitrogen fixing symbiotic system Azolla–Anabaena to improve the quality of treated urban wastewater, particularly on what concerns phosphorus removal efficiencies (40–65%), obtained in continuous assays performed during the past few years and presented earlier, were very promising. Nevertheless, the presence of combined nitrogen in some wastewaters can compromise the treatment efficiency. The main goal of this work was to compare plants behaviour in wastewater and in mineral media with and without added nitrogen.Azolla filiculoides's specific growth rates in wastewater and in mineral media without added nitrogen or with low nitrate concentration were very similar (0.122 d⁻¹–0.126 d⁻¹), but decreased in the presence of ammonium (0.100 d⁻¹). The orthophosphate removal rate coefficients were similar in all the growth media (0.210 d⁻¹–0.232 d⁻¹), but ammonium removal rate coefficient in wastewater was higher (0.117 d⁻¹) than in mineral medium using that source of nitrogen (0.077 d⁻¹).The ammonium present in wastewater, despite its high concentration (34 mg N L⁻¹), didn't seem to inhibit growth and nitrogen fixation, however, in mineral media, ammonium (40 mg N L⁻¹) was found to induce, respectively, 18% and 46% of inhibition.     

Design and operation of a colorimetric detector controller

This report covers the design of a colorimetric detector controller suitable for industrial applications, with a colour detection range of 100 ADMI units. The design is based on the measurement of the response in the blue, green and red light bands covering the 400–700 nm spectrum. The fourth detector is used for detecting ferric ions in the range 0–5 mg l⁻¹ by detecting the colour complex ferri-ferro-cyanide.     

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.     

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.     

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.     

Modified curcumin and dianthrimide methods for the determination of boron in the presence of high levels of nitrate and organics

Modifications have been made to the curcumin and 1,1′-dianthrimide methods for boron analysis so that they may be used in the presence of up to 700 mg l⁻¹NO⁻₃ and 500 mg l⁻¹ organic carbon. In the curcumin method, nitrate is removed by alkaline reduction using a slurry of aluminum powder. In the dianthrimide method, nitrate up to 1000 mg l⁻¹NO⁻₃ is removed in the dehydration-with-sulfuric-acid step; organics are most conveniently removed by treatment of the dehydrated sample with solid potassium persulfate. With dianthrimide, an automated procedure is used for the colour formation and measurement steps.     

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.