Lagooned, secondary effluents as water source for extended agricultural purposes

Chlorination of trickling filter effluents at 40 mg l⁻¹ chlorine for 4 h and 20 mg l⁻¹ for 4 and 6 h showed very limited coliform survival. The number of viruses decreased from a few hundred in 100 ml before chlorination to 0 after chlorination. A 70,000 m³ pond (4 m deep) was used for holding non-chlorinated secondary effluents for 73 days. Bacterial and viral counts were performed every few days. In addition BOD, TC, pH and solar radiation were monitored. After this, the water was pumped out and chlorinated in a pipeline with 8 or 20 mg l⁻¹ chlorine. After chlorination the coliform count was reduced by from 3 to 5 orders of magnitude. After storage for 43 days the non-chlorinated secondary effluents viral count was nil. After chlorination these effluents were also virus-free.

In the second experiment, secondary effluents chlorinated with 20 mg l⁻¹ chlorine with a contact period of 2 h. They were then introduced to the pond. No viruses were found in the incoming water, neither during holding nor after the second chlorination, Coliform regrowth was very slow because of the temperature of the water was only 18–20°C. Identification of the M. Endo membrane filter grown isolated colonies proved that E. coli I disappeared, and all the coliforms were of non-fecal origin or that other growths were non-coliform organisms growing on the MF.

The third experiment was a repetition of the first, in spring, after the temperatures rose. The results confirmed the findings in the first experiment. Therefore, it is thought that 70 days holding of wastewater would permit its extensive agricultural use. For safety, the addition of 20 mg l⁻¹ chlorine to effluents and a short storage could be adequate from a public health point of view.     

Interstitial inorganic phosphorus concentrations in lakes Mendota and Wingra

Interstitial P levels in Lake Mendota and Lake Wingra were evaluated as a function of season and water column and sediment depth. Interstitial water was obtained by the centrifugation-filtration method. Temporal variations were observed over the entire 15 cm sediment depth interval examined in all four locations evaluated. Interstitial reactive P (IRP) levels in Lake Mendota ranged from 0.014–1.67 mg l⁻¹ at the 5–6 m water column depth and from 1.20–5.75 mg l⁻¹ at the 18–19.5 m depth. IRP levels in Lake Wingra ranged from 0.029–2.15 mg l⁻¹ at 3.5 m and from 0.191–3.96 mg l⁻¹ at 2 m. Variations in interstitial P were attributed to variations in oxidation state of Fe as influenced by oxygen transport and reduction rates.     

Productivity and nitrogen balance in large scale phytoplankton cultures

Biomass production and nitrogen balance was studied in 35,000 gal (133,000 1) phytoplankton cultures comprising the first stage in a tertiary sewage treatment-mariculture system. The diatom Phaeodactylum tricornutum persisted for most of the study. At secondary sewage effluent loadings sufficient to produce residual dissolved inorganic nitrogen concentrations above approximately 5 μg atoms l⁻¹, an N:C ratio (molar) of 0.17 was obtained and algal growth was not nutrient-limited. Biomass levels, and hence pond particulate carbon and nitrogen output, varied in response to solar irradiance and dilution rate, but not temperature. Mean winter and summer yields were approximately 1 and 5 g (83 and 417 mg atoms) C m⁻² d⁻¹ respectively. An inverse relationship existed between algal biomass concentration and dilution rate, such that in the late spring optimal pond yields occurred between 0.55 and 0.65 dilutions d⁻¹. Better than 95% dissolved total nitrogen removal was obtained. Net dissolved organic nitrogen production, that would offset dissolved inorganic nitrogen removal, did not occur. Pond particulate nitrogen output was usually less than dissolved total nitrogen removal. Probable explanations for this include (1) ammonia evolution to the atmosphere at high pond pH, (2) particulate nitrogen sedimentation, and (3) denitrification. Of these, the first is believed to be quantitatively the most significant.     

Anaerobic biological treatment of phenol at 9.5-15 degrees C in an expanded granular sludge bed (EGSB)-based bioreactor

The aims of this study were to demonstrate the (1) feasibility of psychrophilic, or low-temperature, anaerobic digestion (PAD) of phenolic wastewaters at 10–15 °C; (2) economic attractiveness of PAD for the treatment of phenol as measured by daily biogas yields and (3) impact on bioreactor performance of phenol loading rates (PLRs) in excess of those previously documented (1.2 kg phenol m⁻³ d⁻¹). Two expanded granular sludge bed (EGSB)-based bioreactors, R1 and R2, were employed to mineralise a volatile fatty acid-based wastewater. R2 influent wastewater was supplemented with phenol at an initial concentration of 500 mg l⁻¹ (PLR, 1 kg m⁻³ d⁻¹). Reactor performance was measured by chemical oxygen demand (COD) removal efficiency, CH₄ composition of biogas and phenol removal (R2 only). Specific methanogenic activity, biodegradability and toxicity assays were employed to monitor the physiological capacity of reactor biomass samples. The applied PLR was increased to 2 kg m⁻³ d⁻¹ on day 147 and phenol removal by day 415 was 99% efficient, with 4 mg l⁻¹ present in R2 effluent. The operational temperature of R1 (control) and R2 was reduced by stepwise decrements from 15 °C through to a final operating temperature of 9.5 °C. COD removal efficiencies of c. 90% were recorded in both bioreactors at the conclusion of the trial (day 673), when the phenol concentration in R2 effluent was below 30 mg l⁻¹. Daily biogas yields were determined during the final (9.5 °C) operating period, when typical daily R2 CH₄ yields of c. 3.3 l CH₄ g⁻¹ COD_removed d⁻¹ were recorded. The rate of phenol depletion and methanation by R2 biomass by day 673 were 68 mg phenol g VSS⁻¹ d⁻¹ and 12–20 ml CH₄ g VSS⁻¹ d⁻¹, respectively.     

Decolorization of an azo dye by unacclimated activated sludge under anaerobic conditions

Studies on the reductive decolorization of a complex azo dye, Reactive Red 3.1, were made as part of the development of a practical approach to better exploit the metabolic potential of biomass in wastewater treatment. Decolorization was achieved at low and variable rates by mixed microbial cultures under various environmental conditions, including low pH and high salt concentration. It was caused by reductive cleavage of the azo bond to yield two aromatic amines. More reliable and effective decolorization rates, of up to 20–30 mg l⁻¹ h⁻¹, were given by unadapted activated sludge, (6 g l⁻¹) incubated with 400 mg l⁻¹ of Reactive Red 3.1 under anaerobic conditions. Decolorization also occurred best in static conditions.     

A rational approach to the design of wastewater-fed fishponds

A procedure is given for the minimal treatment of wastewater in a 1-day anaerobic pond followed by a 5-day facultative pond prior to discharge into a fishpond. The criterion for the design of the fishpond is a surface loading of total nitrogen of 4 kg N ha⁻¹ d⁻¹. The number of faecal coliforms in the fishpond is then determined; this should be 1000 per 100 ml to ensure that the fish are microbiologically safe for human consumption. Fish (carp and tilapia) yields are of the order of 13 t ha⁻¹ a⁻¹, assuming that the pond is drained and harvested three times a year and that there is a fish loss of 25 percent. Preliminary financial analysis indicates that such a wastewater-fed fishpond system is commercially viable.     

Effect of water hardness on the toxicity of cadmium to micro-organisms

A study was made of the effect of water hardness at different concentrations (viz. 0, 80, 120, 160, 240, 320, 400 and 480 mg l⁻¹ as CaCO₃) on the toxicity of cadmium metal (5 mg 1⁻¹) as sulphate to saprophytic and nitrifying bacteria, with respect to the rate constant (K) and ultimate biochemical oxygen demand (L) which were calculated from BOD data (15 days) using the Thomas Graphical Method. Glucose was used as a source of carbon for micro-organisms. It was observed that the toxicity of cadmium to micro-organisms (both saprophytic and nitrifying) decreased with increasing hardness and reached a maximum at 320 mg 1⁻¹ as CaCO₃ for nitrifying and 400 mg l⁻¹ as CaCO₃ for saprophytic bacteria. After these hardness levels, the ultimate BOD (L) and rate constant (K) showed a decrease. Nitrifying bacteria were found to be more sensitive to the metal as well as to its complexation with calcium or with other ions as they retained their normal activity at a lower hardness level as compared to saprophytic bacteria.     

Treatment of raw domestic sewage in an UASB reactor

The treatment of raw domestic sewage at ambient temperatures in an upflow anaerobic sludge blanket (UASB) reactor with a volume of 120 l. and a height of 1.92 m was studied. The sewage had an average BOD₅ of 357 mg l⁻¹ and COD of 627 mg l⁻¹. Approximately 75% of the organic materials were in the suspended fraction. The sewage temperature ranged from 18 to 28°C during the experimental period. The reactor operated continuously for 9 months and assessed self-inoculation and raw domestic sewage purification. The unit was started without inoculum and ran during the entire experimental period with a hydraulic retention time of 4 h. During the experiment, a sludge bed build-up was observed. At the end of the experimental period, the predominance of spherical granular particles up to 6–8 mm in diameter was evident.

After a 4-month operation, it was observed that the inoculation/acclimatization steps had been concluded. Removal efficiencies of BOD₅ = 78%, COD = 74% and TSS = 72% were obtained. A typical gas production factor of 80 l kg⁻¹ COD added was observed and the CH₄ content of the biogas was 69%.     

Effect of surfactants on the determination of fluoride in waters

Eleven surfactants representing pure cationic anionic and nonionic detergents, four commercial detergents, sodium pyrophosphate, sodium tripolyphosphate, a soap and nitrilotriacetic acid were investigated for their effect on the spectrophotometric and specific ion electrode determinations of fluoride in water. Cationic, anionic and nonionic detergents at concentrations up to 50, 400 and 1000 mg l⁻¹, respectively, gave 5% error or less in the determination of fluoride. Sodium tripolyphosphate interfered badly above 1.5 mg l⁻¹, and therefore the interference by formulated detergents containing tripolyphosphate was large. The fluoride ion activity electrode method is the most suitable procedure for the determination of fluoride in polluted waters containing surfactants.     

Wheat straw as substrate for water denitrification

Biological denitrification of drinking water was studied in up-flow laboratory reactors packed with wheat straw which served as the sole carbon source as well as the only physical support for the microorganisms. The highest rates of denitrification (0.053 g N removed l⁻¹ d⁻¹) were observed in fresh reactors during their first week of operation and the efficiency of the process declined thereafter. The addition of fresh wheat straw brought about a temporary improvement of the denitrification performance and a regime of one weekly addition prevented the deterioration of a reactor which was operated for 5 months. The rate of denitrification was affected by the water velocity and decreased at velocities above 0.054 m d⁻¹. Colour and soluble organic carbon associated with fresh straw were removed by adsorption on powdered activated carbon.     

Complexation of copper in the effluent of a sewage treatment plant and an estimate of its influence on toxicity to coho salmon

Measurements by cupric ion electrode of the complexing capacity of the effluent from a sewage treatment plant (STPE) averaged 0.300 mg 1⁻¹. Of the complexed Cu 67% was due to compounds of 10,000 MW. Organic compounds removable by activated carbon composed 88% of the total organic carbon and were responsible for 87% of the complexation. Complexation of Cu²⁺ by STPE diminishes the toxicity from total Cu to juvenile coho salmon; the LC₅₀ was 0.164 mg 1⁻¹ for river water vs 0.286 mg 1⁻¹ for 40% STPE. The LC₅₀ of Cu²⁺ was approximately the same (0.017 vs 0.022 mg 1⁻¹) in both matrices; this species thus appears to play a toxic role. The mean survival time in diluted STPE with added Cu was inversely proportional to the Cu²⁺ concentration.     

Effect of settling on performance of the upflow anaerobic sludge bed reactors

The effects of settler volume on the start-up and steady-state performance of 41. laboratory upflow sludge bed reactors treating bean blanching waste of 10,000 mg COD l⁻¹ were determined. The rate of start-up, as well as the maximum loading rate, increased with increased settler volume and performance. A loading rate of 30 kg COD m⁻³ day⁻¹ (based on reactor volume alone) and a COD removal of 95% was obtained with a 21. settling flask and a 4 to 1 recirculation rate. Without a settler, the maximum loading rate was 10 kg COD m⁻³ day⁻¹. The sludge was flocculent rather than granular. Sludge profiles and characteristics in the reactors and settlers were determined.     

Mobilization of some metals in water and animal tissue by NTA, EDTA and TPP

Parallel experiments were conducted under stagnant and flowing conditions to determine whether sodium tripolyphosphate (TPP), the conventional detergent builder, or two potential replacements, nitrilotriacetic acid (NTA) and ethylene—diaminetetraacetic acid (EDTA) significantly influenced the mobilization of major cations (Ca, Mg, Na, K) and some heavy metals (Fe, Mn, Zn, Cu, Pb, Cr). Water sediments and tissue of chironomid adults (Chironomus tentans Fabricius), crayfish (Orconectes virilis Hagen) and rainbow trout (Salmo gairdnerii Richardson) were examined. The results showed that the chelating agents applied in concentrations of 0.2–5.0 mg 1⁻¹ often increased the concentration of iron, manganese, lead and zinc in water above contaminated lake sediments. Other heavy metals were not affected significantly. EDTA was the most active mobilizing agent while NTA and TPP both had a less significant effect. The chelating agents generally had little effect on the rate of uptake of most metals by chironomids in aquaria. The role of chelating agents in flowing systems was even less pronounced. Zinc concentrations in water were significantly elevated by the treatment with 1 mg 1⁻¹ EDTA and manganese concentrations were significantly higher in trout from the pond treated with an intermediate level (1 mg 1⁻¹) of NTA. All other treatments yielded levels of major ions and heavy metals that were not significantly different from those in the control ponds.     

Removal of saxitoxins from drinking water by granular activated carbon, ozone and hydrogen peroxide--implications for compliance with the Australian drinking water guidelines

In a laboratory-scale trial, we studied the removal of saxitoxins from water by ozone, granular activated carbon (GAC) and H₂O₂, and considered the implications of residual toxicity for compliance with the Australian drinking water standards. Cell-free extracts of Anabaena circinalis were added to raw, untreated drinking water obtained from a water supply reservoir to provide a toxicity of 30 μg (STX equivalents) l⁻¹. Ozone alone, or in combination with H₂O₂, failed to destroy the highly toxic STX and GTX-2/3, and only partially destroyed dc-STX, and the low-toxicity C-toxins and GTX-5. In all cases, the toxicity of the water was reduced by less than 10%. GAC removed all of the STX, dc-STX and GTXs, but only partially removed the C-toxins. However, the residual toxicity was reduced to the suggested Australian drinking water guideline concentration of 3 μg (STX equivalents) l⁻¹ without O₃ pre-treatment. Modelling the spontaneous chemical degradation of residual C-toxins following treatment shows that residual toxicity could increase to 10 μg l⁻¹ after 11 d due to formation of dc-GTXs and would then gradually decay. In all, residual toxicity would exceed the Australian drinking water guideline concentration for a total of 50 d.     

Stratification in laboratory simulations of shallow stabilization ponds

The paper describes the biochemical stratification that occurs in shallow stabilization ponds. It appears from the study of chemical and biological parameters that stratification does occur in ponds as shallow as 35.5 cm. The depth of the upper aerobic zone appears to be constant in most of the cases and depends only on the available light. The algae only grow up to a depth where the light attenuation becomes 96% of the original effective light intensity of 60 cal cm⁻² day⁻¹ on the surface of the pond.     

Aerobic treatment of piggery waste

The operating characteristics of laboratory waste treatment systems were studied during the aerobic degradation of pig excrement at different loading rates and temperatures. The treatment systems were of two types: one was operated with floc formation and gravity separation of liquid and suspended solid effluents; and a second was operated without floc formation or separation of the effluent into liquid and solid fractions.

With an operating temperature of 15°C the parameters most affected by loading rate were (1) the concentrations of suspended solids and chemical oxygen demand in the liquid effluent; (2) the pH value of the mixed liquor; (3) nitrification; (4) the BOD of the supernatant from the mixed liquor; and (5) output of suspended solids as a percentage of input.

The concentrations of suspended solids and chemical oxygen demand in the liquid effluents were little affected by loading rates in the range 0·05-0·15 g SS g MLSS⁻¹ d⁻¹ (0·02-0·06 g BOD g MLSS⁻¹ d⁻¹) but increased with increasing loading rate in the range 0·15-0·30 (0·06-0·12 BOD). At loading rates below about 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) the mixed liquors were acidic, with pH values down to 5·2, whereas at loading rates above about 0·80 (0·32 BOD) they were alkaline, with pH values up to 8·9. At intermediate loading rates the mixed liquor pH value was more variable though in general the higher the loading rate the higher also the pH value of the mixed liquor. Acidic conditions in the mixed liquors were attributed to the occurrence of nitrification, while in the absence of nitrification the mixed liquors remained alkaline. The concentration of BOD₅ in the supernatant from the mixed liquors increased with increasing loading rate from about 35 mg 1⁻¹ at a loading rate of 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) to about 250 mg 1⁻¹ at a loading rate of 1·30 (0·52 BOD). The output of suspended solids from the treatment systems represented about 70 per cent of input suspended solids at loading rates of about 0·15 g SS g MLSS⁻¹ d⁻¹ (0·06 g BOD g MLSS⁻¹ d⁻¹) and increased to about 100 per cent at loading rates of 0·80 (0·32 BOD). Output of chemical oxygen demand was about 60 per cent of input at the lower loading rates and 80–90 per cent at the higher ones.

Operation of treatment units at temperatures of 5 and 10°C instead of 15°C had little effect on the efficiency of degradation at loading rates in the range 0·085-0·20 g SS g MLSS⁻¹ d⁻¹ (0·034-0·08 g BOD g MLSS⁻¹ d⁻¹), but nitrification was prevented at 5°C. At loading rates of 0·77 (0·31 BOD) and 1·46 (0·58 BOD) operation at 25°C appeared to increase the amount of degradation as compared with that achieved at 15°C.

The practical implications of the results and possible future approaches to the aerobic treatment of farm wastes are discussed.     

Estimate of treatment plant effluent impact on chloride concentrations and oyster environment within the murderkill river estuary

The Murderkill River is a partially tidal body of water with summer-time 50-percentile freshwater flows ranging from 17.9 to 27.6ft³s⁻¹ (0.5 to 0.77m³s⁻¹) at a point coincident with the effluent discharge from the Kent County Regional Wastewater Treatment Plant (start-up late 1972). Chloride concentrations were determined over six summers to characterize river conditions prior to start-up of the 10-million gal day⁻¹ (37.850 m³ day⁻¹) (design) plant. Use of a one-dimensional steadystate model for a conservative substance shows that chloride values would be reduced by up to 20% at low water slack (LWS) periods for wastewater flows of 10 million gal day⁻¹ (37,850 m³ day⁻¹). The LWS chloride concentrations in the area of oyster production would be reduced to 3–6 ppt (5.9–10.8 ppt salinity) for wastewater loadings greater than 10 million gal day⁻¹ (37,850 m³ day⁻¹) . It is suggested that chloride additions in the treatment plant effluent be implemented to maintain minimum summertime low-water-slack levels of 5.6 ppt chloride (10 ppt salinity), consistent with a proper environment for oyster development.     

Uptake and release of zinc by aquatic bryophytes (Fontinalis antipyretica L. ex. Hedw.)

The zinc uptake and posterior release by an aquatic bryophyte—Fontinalis antipyretica L. Ex Hedw.—was experimentally studied in laboratory exposing the plants to different zinc concentrations in the range, 1.0–5.0 mg l⁻¹, for a 144 h contamination period, and then exposed to metal-free water for a 120 h decontamination period. The experiments were carried out in perfectly mixed contactors at controlled illumination, using mosses picked out in February 1997, with a background initial zinc concentration of 263 mg g⁻¹ (dry wt.). A first-order mass transfer kinetic model was fitted to the experimental data to determine the uptake and release constants, k₁ and k₂, the zinc concentration in mosses at the end of the uptake period, C_mu, and at the equilibrium, for the contamination and decontamination stages, C_me and C_mr, respectively. A bioconcentration factor, BCF=k₁/k₂ (zinc concentration in the plant, dry wt./zinc concentration in the water) was determined. A biological elimination factor defined as BEF=1−C_mr/C_mu was also calculated. BCF decreases from about 4500 to 2950 as Zn concentration in water increases from 1.05 to 3.80 mg l⁻¹. BEF is approximately constant and equal to 0.80. Comparing Zn and Cu accumulation by Fontinalis antipyretica, it was concluded that the uptake rate for Zn (145 h⁻¹) is much lower than for Cu (628 h⁻¹) and the amount retained by the plant decreased by a factor of about seven.     

A simple method for concentrating and detecting viruses in wastewater

A simple method has been developed for routine analysis of sewage and sewage effluents for detecting viruses using adsorption at pH 3 on a 0·45 μm 47 mm diameter membrane filter and elution at pH 8. It was tested on viruses added to autoclaved sewage. Homogenizing the sample for 4 min in a Waring blender and clarification by centrifugation at 1800 g and later at 9230 g facilitated easy filtration without any loss of virus. Retention of the eluant for 30 min on the millipore membrane and then elution in situ under suction provided a sterile eluate with 100 per cent recovery of viruses.

Viruses added to fecal suspensions with 600 mg I⁻¹ BOD were completely recovered when the sample pH was adjusted to 3 and its salt concentration increased by adding 1200 mg l⁻¹ of Mg²⁺ as the chloride. This procedure eliminated the need for passing the samples through ion exchange resins for removing membrane coating components. In a 1 yr programme of monitoring of raw sewage from a middle income group community in Nagpur, a maximum of 3150 PFU/1 during monsoon and 11575 PFU/1 during winter was obtained.

High efficiency and reproducibility of the method allowed the use of sample volumes of 40 ml of raw sewage and 320 ml of treated effluent for the detection of viruses.     

Fish toxicity of jet fuels—I. The toxicity of the synthetic fuel JP-9 and its components

The toxicity of the jet fuel JP-9 and its components RJ-4, RJ-5 and MCH was assessed in static bioassays on the warm water fish, golden shiner (Notemigonus chrysoleucas). The 96-h LC₅₀ of emulsions was 2.0 mg 1⁻¹ for JP-9, 0.51 mg 1⁻¹ for RJ-4, 0.61 mg 1⁻¹ for RJ-5 and 72 mg 1⁻¹ for MCH. As determined by the 96-h LC₅₀ values unemulsified fuel (pools of fuel) JP-9 was 235 times less toxic, RJ-4 was 196 times less toxic, RJ-5 was 7700 times less toxic and MCH was 3.3 times less toxic than the corresponding emulsified materials.

In continuous flow bioassays with the water soluble fraction of the fuel and its components the effect on egg hatchability and fry development of flagfish (Jordanella floridae) and rainbow trout (Salmo gairdneri) was studied. The no effect of level on flagfish egg hatchability was 0.23 mg 1⁻¹ for JP-9 and 0.05 mg 1⁻¹ for RJ-5. Concentrations of 0.83 mg 1⁻¹ MCH and 0.2 mg 1⁻¹ RJ-4 did not affect egg hatchability. In rainbow trout studies 97-day LC₅₀ values for RJ-4 and RJ-5 were 0.045 mg 1⁻¹ and 0.072 mg 1⁻¹, respectively, and 23-day LC₅₀ values for JP-9 and MCH were 0.26 mg 1⁻¹ and 1.3 mg 1⁻¹, respectively.

The accumulation of fuels in fish bodies was studied and it was found that flagfish can tolerate a total body burden of 0.5 mg MCH g⁻¹ wet weight without lethality. It was also found that body burdens of 0.43 mg RJ-4 g⁻¹ and of 0.27 mg RJ-5 g⁻¹ on a wet weight basis will produce 50% mortality in rainbow trout.

Voiding of MCH from fish bodies occurs readily in fuel-free water, but RJ-4 and RJ-5 are retained in the tissues.