Aquacultural approaches to recycling of dissolved nutrients in secondarily treated domestic wastewaters—III uptake of dissolved heavy metals by artificial food chains

We have studied the biological productivity, measured as biomass yields, of laboratory scale artificial food chains composed of sequential monocultures of suspended unicellular green algae (Scenedesmus), herbivorous cladoceran crustaceans (Daphnia magna), and herbivorous teleost fish (Hypophthalmichthys). These food chains were grown in minimally modified secondarily treated, chlorinated then dechlorinated, domestic waste waters. Successive stages in the chains were fed the organisms grown in the just preceding stages.Additions of 1 ppm ferrous sulfate and aeration with mixtures of air plus 5% carbon dioxide (buffered cultures) increased yields of Scenedesmus cultures by 52% above yields of air aerated, unsupplemented cultures (unbuffered cultures). Buffered cultures remained stable for long periods (1–2 weeks) and maintained good cell quality (no chlorosis; 90+% of cells present were Scenedesmus). Unbuffered, unsupplemented cultures soon became chlorotic, cells autoflocculated (which greatly reduced yields), and changes occurred in species composition. These latter cultures were unsuitable as food for cladocerans.Three production indices (conversion coefficients, specific production, and production/biomass ratios) showed that better growth occurred in cladoceran cultures fed buffered algal cultures as compared with unbuffered cultures. When fed unbuffered cultures cladocerans showed higher production indices when flocculated but unsettled cultures were used, as compared with supernates from flocculated, settled cultures.Attempts to grow the primarily herbivorous silver carp (Hypophthalmichthys molitrix) in a two-stage (buffered algae-fish) food chain failed. Ammonia toxicity may have been the cause of fish deaths.     

Operation of a deep, well-mixed, high-rate photosynthetic oxidation pond

The maximum depth for the stable operation of a photosynthetic high-rate oxidation pond was found to be 90cm. At this depth, both the pH and the peak oxygen concentration were significantly lower than the values obtained in shallow high-rate oxidation ponds.     

Microalgal biomass production by using ultra- and nanofiltration membrane fractions of olive mill wastewater

Olive milling produces huge amounts of wastewater (OMWW) characterized by an extremely high organic load. Its polyphenols content is a hindrance to conventional biological treatment and to using it as growing medium for common microbial biomasses. The practice to dump it on soil is in conflict with the latest EU directives about waste management.OMWW can be effectively and efficiently treated by means of membrane technology to a fraction of the initial volume, but membrane processing concentrates still require treatment. Reversing the overall cost balance of membrane processing and subsequent treatment requires valorizing the concentrates through their reuse, as well as ensuring long-term service of the membrane system through effective wastewater pretreatment and sustainable, fouling-controlling, membrane operation conduite.Aim of this work is to reuse and valorize the ultra- and nanofiltration membrane concentrates as media for biomass production of microalgae and cyanobacteria. Scenedesmus dimorphus and Arthrospira platensis, usable as a food, feed, nutraceutical component or feedstock for biofuels, were selected for this investigation. Microalgal growth was experimentally determined and related to the composition of the concentrate-based media and to the irradiance distribution within the photobioreactor volume to decouple light limitation and medium chemical composition effects.     

Bod removal rates of waste stabilization ponds as a function of loading, retention time, temperature and hydraulic flow pattern

This study evaluates the influence of loading, detention time and temperature on the first order BOD removal coefficient K₁. Numerical values of K₁ are derived from semi-continuous-flow laboratory units of sewage ponds and introduced into the design formula for a multi-stage continuous flow reactor. There was a good correspondence (r = 0.92) between the computed BOD removal rates and the empirical results obtained from three large-scale multi-stage pond systems.     

The effect of beaver ponds on the nonpoint source water quality of a stream in Southwestern Wyoming

Currant Creek, a second order stream in southwestern Wyoming, has three large complexes of beaver ponds midway along its 32 km length. To determine whether these ponds improve the quality of water flowing through them, during spring and summer of 1984 and 1985 water samples were taken upstream from, within, and downstream from the pond complexes. During periods of high flow (i.e. spring runoff), concentrations of suspended solids (SS), total phosphorus (TP), sodium hydroxide-extractable phosphorus (NaOH-P, an index of biologically available P) and total Kjeldahl nitrogen (TKN) were reduced in water flowing through the beaver ponds. During low flow, beaver ponds had less effect on these parameters. Concentrations of nitrate nitrogen (NO₃-N) were reduced during both high and low flows, while concentrations of ortho-phosphate (ortho-P) did not appear to be affected by beaver ponds. Ammonia nitrogen almost always was at the limit of detection. Regression of NaOH-P versus [SS plus ortho-P] suggested that the primary source of NaOH-P was SS. In general, SS explained a large portion of the variation in TP, TKN, and NaOH-P, and often ortho-P was significantly correlated to TP. The increase in the concentration of most parameters below the area with dam complexes appears to reflect input from bank and channel erosion, and export of SS, TP, TKN and NO₃-N from beaver dam complexes was calculated to be less than that from stream sections above or below the dams. Thus the location of dams should be considered before using them to try and improve water quality. The apparent importance of bank and channel erosion as the primary source of nutrients to Currant Creek contrasts with many watersheds in agricultural areas.     

The dynamics of suspended algal populations in the lower Wye catchment

The algae of the R. Wye and its tributary the R. Lugg were described principally from samples collected from 7 sites in the lower Wye catchment during 1980 and 1981. The density of algae in the Wye was found to be correlated with river flow and solar radiation, highest numbers (12.5 × 10⁵ cells ml⁻¹), principally of Scenedesmus and Cyclotella, occurring at low stable flows and relatively high solar radiation. Algal populations in the Lugg were much smaller ( 1.3 × 10³cells ml⁻¹) than those of the Wye and were principally composed of species derived from the periphyton. Downstream increases in load (cell density × flow) of both Scenedesmus and Cyclotella in the Wye were generally equivalent to about 0.3 division d⁻¹; these rates were lower than those obtained in laboratory culture and this was probably largely related to underestimates arising from algal removal by filter feeders (principally simuliid larvae). Potential problems arising from the treatment of Wye water supporting substantial algal growths are considered: these include haloform production, deoxygenation in a transfer pipeline, algal penetration into potable supply and taste and odour.     

Characterizing nutrient dynamics with relation to changes in partial pressure of CO2 in a tropical sewage‐fed aquaculture pond situated in a Ramsar wetland

The changes in nutrient dynamics (nitrate, ammonium, silicate, phosphate and iron concentration) vis‐à‐vis partial pressure of CO₂ in water [pCO₂(water)] from tropical sewage‐fed aquaculture ponds (East Kolkota Wetlands, India) were analysed by means of a microcosm. A significant relationship between these nutrient’s removal from the system and reduction in pCO₂(water) was observed (with few exceptions). These water bodies acted as significant sources of CO₂ in pre‐monsoon and monsoon seasons despite having substantial quantity of chlorophyll‐a to make it a net autotrophic system. The study revealed that if conditions favourable for optimum photosynthesis can be maintained in these ponds, the CO₂ source character of these ponds can be reversed. In the post‐monsoon season, when the pH of the water column was high, the system acted as sink for CO₂ which suggests the use of lime to prevent these systems from becoming hypereutrophic and carbon source at the same time.     

Short‐term effects of planktonic rotifers and cladocerans on phytoplankton of the River Nile

The responses of River Nile phytoplankton to different zooplankton communities have been analyzed. Different communities have been made up of natural Nile water of rotifers and small cladocerans, rotifers after exclusion of macrozooplankton by size fraction and large cladocerans plus small cladocerans and rotifers. A set of experiments in enclosures were designed to determine the short‐term effects produced by these zooplankton assemblages on phytoplankton structure. The phytoplankton community are made up of Bacillariophyceae, Cyanophyceae and Chlorophyceae, as the main algal groups. It seems that, grazing does not play a leading role in controlling phytoplankton production and its standing stock in the River Nile.     

How common goldfish could save cities from flooding

Recently, there has been wide national (various British newspapers) and even international (German radio) public interest in Scottish experiments that introduce Carassius auratus (common goldfish) into sustainable urban drainage systems (SUDS), which have been applied to combat flooding. Moreover, dog faeces were added to these systems to simulate contaminated urban runoff. The purpose of this novel and timely research is to increase public acceptance of zero discharge infiltration ponds, and to control algal growth with C. auratus. Findings show that C. auratus improve most water quality variables after their introduction to planted and unplanted infiltration ponds despite deterioration of virtually all common inflow water quality variables based on an annual comparison. Public interest is high because the study captures the imagination of the urban population facing recurrent flooding problems in autumn in low‐lying areas, and the nuisance of dog excrements despite of new regulations to scoop up droppings.     

The toxic effect of copper on algae and rotifers from a Soda Lake (Lake Nakuru, East Africa)

The effect of Cu(II) ions on the photosynthetic oxygen production of the phytoplankton, the growth rate of the blue-green algae Spirulina platensis and the population of rotifers (Brachionus sp.) in water from the soda lake Nakuru in Kenya was investigated experimentally. The photosynthetic production was reduced to 80% of the control by the addition of 0.1 mg Cu l⁻¹ and 50% by addition of 0.15–0.20 mg Cu l⁻¹. The growth rate of Spirulina platensis was more affected by copper than the photosynthesis of phytoplankton. Addition of 0.05 mg Cu l⁻¹ reduced the growth rate to about 40% of the control. The rotifiers were less sensitive to copper than the algae, but after 8 days exposure to 0.5 mg Cu l⁻¹ or more the population was severely affected.     

Towards a luxury uptake process via microalgae - Defining the polyphosphate dynamics

Microalgae in waste stabilization ponds (WSP) have been shown to accumulate polyphosphate. This luxury uptake of phosphorus is influenced by the wastewater phosphate concentration, light intensity and temperature, but the dynamics of how these factors affect luxury uptake with respect to time are not understood. With improved understanding of the dynamics of this mechanism and how it could be manipulated, a phosphorus removal process utilizing luxury uptake by microalgae might be developed. In this work, luxury uptake was investigated by chemical extraction of the acid-soluble and acid-insoluble fractions of polyphosphate in the microalgae. The results showed that the initial accumulation and subsequent utilization of both acid-soluble polyphosphate (ASP) and acid-insoluble polyphosphate (AISP) is a function of the wastewater phosphate concentration. It was found that light intensity influenced both the accumulation and utilization of ASP. The temperature influenced the accumulation of AISP. AISP is believed to be a form of phosphorus storage and ASP is involved in metabolism however, the results of this work show that ASP can also act as a short term form of phosphorus storage. To optimize luxury uptake by microalgae a ‘luxury uptake pond’ is proposed where the conditions the microalgae are exposed to can be manipulated. This ‘luxury uptake pond’ would be designed to expose the microalgae to a high phosphate concentration and high light intensity for a short period of time in order to achieve optimal polyphosphate accumulation. Subsequent harvesting would then remove the phosphorus rich microalgae from the system.     

Survival in maturation ponds of coliform bacteria with transferable drug resistance

The behaviour of drug-resistant coliform bacteriasin a series of sewage maturation ponds was investigated. The average reduction through the ponds of coliforms resistant to ampicillin, chloramphenicol, kanamycin, streptomycin or tetracycline was 6.83 per cent lower than that of drug-sensitive bacteria. This difference was mainly due to coliforms with transferable resistance (R⁺ coliforms) which increased from 0.86 per cent to 2.45 per cent through the ponds. The spectrum of transferable resistance of coliforms in the effluent did not differ notably from that of coliforms in the influent. The average incidence of Escherichia coli I among R⁺ coliforms decreased from 66.08 per cent to 62.09 per cent. This indicates that low-level transfer of R factors may occur in ponds. Possible mechanisms and the epidemiological significance of the increased survival of R⁺ coliforms in maturation ponds are discussed.     

Environmental risk assessment of white phosphorus from the use of munitions — A probabilistic approach

White phosphorus (P₄) is a highly toxic compound used in various pyrotechnic products. Ammunitions containing P₄ are widely used in military training areas where the unburned products of P₄ contaminate soil and local ponds. Traditional risk assessment methods presuppose a homogeneous spatial distribution of pollutants. The distribution of P₄ in military training areas is heterogeneous, which reduces the probability of potential receptors being exposed to the P₄ by ingestion, for example. The current approach to assess the environmental risk from the use of P₄ suggests a Bayesian network (Bn) as a risk assessment tool. The probabilistic reasoning supported by a Bn allows us to take into account the heterogeneous distribution of P₄. Furthermore, one can combine empirical data and expert knowledge, which allows the inclusion of all kinds of data that are relevant to the problem. The current work includes an example of the use of the Bn as a risk assessment tool where the risk for P₄ poisoning in humans and grazing animals at a military shooting range in Northern Norway was calculated. P₄ was detected in several craters on the range at concentrations up to 5.7 g/kg. The risk to human health was considered acceptable under the current land use. The risk for grazing animals such as sheep, however, was higher, suggesting that precautionary measures may be advisable.     

Elimination of Salmonella in stabilization ponds

While the reduction of putrescible organic matter is important in sewage treatment, the microbiological quality of the effluents is of great public health significance, since these are usually discharged into streams or onto land. The performance of two types of stabilization ponds located at Nagpur, India, was studied with respect to the reduction of Salmonella, Coliforms, E. coli and faecal streptococci. The two ponds were operated at different BOD loading and detention time. Furthermore while one had two cells with submerged interconnection the other had three cells interconnected with a surface overflow arrangement. Comparing the results of these two ponds, treating domestic sewage, it is found that Salmonella does not get eliminated in the two celled pond while they are absent in 1 litre aliquots of effluent samples from the three celled pond. The indicator organisms are reduced to a great extent in the latter pond as compared to the former. From this it appears that the number of cells and the interconnecting arrangements are very important besides the loading, detention period and other design features.     

Alum clarification for improving wastewater effluent quality

This paper presents results of an investigation on the application of alum for improving the overall performance of wastewater treatment plants. These studies were conducted on a pilot scale of 7200 gal day⁻¹. The pilot plant incorporated parallel systems for evaluating conventional and high-rate clarification. The conventional system included chemical addition, rapid mix, flocculation, sedimentation, and rapid sand filtration. The high-rate system differed in that the flocculated solids were introduced directly onto a dual-media filter with no intermediate sedimentation.Results of this study indicate that in both types of tertiary clarification treatment, greater than 95 per cent removal of the BOD of a nitrified secondary effluent, turbidity, and suspended solids were achieved with alum doses of 40–60 mg 1⁻¹. Efficient phosphorus removals were also realized in the same systems by increasing the alum dose to about 150 mg 1⁻¹. In addition to the removal of BOD and phosphorus, bacteria and heavy metals were removed.     

Aquacultural approaches to recycling of dissolved nutrients in secondarily treated domestic wastewaters-II biological productivity of artificial food chains

We have studied the biological productivity, measured as biomass yields, of laboratory scale artificial food chains composed of sequential monocultures of suspended unicellular green algae (Scenedesmus), herbivorous cladoceran crustaceans (Daphnia magna), and herbivorous teleost fish (Hypophthalmichthys). These food chains were grown in minimally modified secondarily treated, chlorinated then dechlorinated, domestic waste waters. Successive stages in the chains were fed the organisms grown in the just preceding stages.Additions of 1 ppm ferrous sulfate and aeration with mixtures of air plus 5% carbon dioxide (buffered cultures) increased yields of Scenedesmus cultures by 52% above yields of air aerated, unsupplemented cultures (unbuffered cultures). Buffered cultures remained stable for long periods (1–2 weeks) and maintained good cell quality (no chlorosis; 90+% of cells present were Scenedesmus). Unbuffered, unsupplemented cultures soon became chlorotic, cells autoflocculated (which greatly reduced yields), and changes occurred in species composition. These latter cultures were unsuitable as food for cladocerans.Three production indices (conversion coefficients, specific production, and production/biomass ratios) showed that better growth occurred in cladoceran cultures fed buffered algal cultures as compared with unbuffered cultures. When fed unbuffered cultures cladocerans showed higher production indices when flocculated but unsettled cultures were used, as compared with supernates from flocculated, settled cultures.Attempts to grow the primarily herbivorous silver carp (Hypophthalmichthys molitrix) in a two-stage (buffered algae-fish) food chain failed. Ammonia toxicity may have been the cause of fish deaths.     

Impact of oil and oil-dispersant mixtures on the fauna of freshwater ponds

In a series of 5 artificial ponds, one was treated with a nominal concentration of 100 ppm of crude oil, two others were treated with a nominal 100 ppm of oil and 20 ppm of dispersant. Mesozooplankton populations were reduced in the oil-treated pond relative to the control pond, and eliminated in the oil-dispersant ponds. This condition persisted until the following year when the mesozooplankton was similar in all ponds. The protozooplankton experienced species shifts with Halteria and Strobilidium being eliminated initially in all treated ponds, but Halteria was collected in samples the following spring. Other protozoans such as thecamoebae increased in the treated ponds, while others, like zooflagellates, did not appear to be affected by the chemicals. Zoobenthos was affected by treatment, with the number of different types being reduced. The zoobenthos had recovered in one of the treated ponds the following spring, and that in the other treated ponds were recovering. Surface insects were eliminated after treatment, but recolonized during the next spring. Nekton were initially reduced by treatment. The population changes are discussed with respect to the fate of oil.     

Life history responses of Daphnia magna feeding on toxic Microcystis aeruginosa alone and mixed with a mixotrophic Poterioochromonas species

The toxic effects of a mixotrophic golden alga (Poterioochromonas sp. strain ZX1) and a cyanobacterium Microcystis aeruginosa grazed by Poterioochromonas to a cladoceran were investigated through life history experiments using Daphnia magna. Poterioochromonas cultured in two ways (fed M. aeruginosa in an inorganic medium or grown in an organic medium) both induced starvation-like effects on D. magna, indicating that Poterioochromonas is neither acutely toxic nor a good food for D. magna. Despite a microcystin-LR content of 10⁻⁸ μg cell⁻¹ in M. aeruginosa, no toxins were accumulated in Poterioochromonas fed the cyanobacterium. The toxic effect of M. aeruginosa to D. magna was significantly reduced in the presence of Poterioochromonas, which may be performed in two ways: decrease M. aeruginosa cells ingestion of D. magna by grazing on M. aeruginosa; and decrease the toxicity of the medium by degrading the toxins released by M. aeruginosa. This study provides new information on the interactions between a cyanobacterium and its grazer under laboratory conditions and may increase our understanding of the ecological significance of such interactions in the aquatic food webs.     

Experimental investigations of direct injection compression ignition engine by using Coconut,and Karanja biodiesel fuels with emulsions of microalgae based antioxidant

The Compression Ignition (CI) engines are playing vital role in the transportation sector; because of their lower maintenance cost even. The practice of Diesel or biodiesel is increasing Green House Gases (GHG) such as NO_x, particulate matter in the environment. Among all GHG emissions, NO_x is most harmful to human, environment. The use of additives in Diesel, biodiesel their blends in CI engine is very well practicing fuel modification technique to reduce GHG emissions. The higher cost of phenol, amine-based antioxidants are causing to increase CI engine operating cost. In this work, to investigate unmodified Direct Injection Compression Ignition engine characteristics. The Mixed culture Microalgae (MCM) biomass particles used as an antioxidant additive in pure Coconut, Karanja biodiesel. The brake thermal efficiency improved because of the explosion of MCM particles. The NO_x emissions reduced due to the absorption of heat from the combustion chamber by microalgae particle.     

A sustainable, carbon neutral methane oxidation by a partnership of methane oxidizing communities and microalgae

Effluents of anaerobic wastewater treatment plants are saturated with methane, an effective greenhouse gas. We propose a novel approach to treat such effluents using a coculture of methane oxidizing communities and microalgae, further indicated as methalgae, which would allow microbial methane oxidation with minimal CO₂ emissions. Coculturing a methane oxidizing community with microalgae in sequence batch reactors under continuous lightning yielded a factor of about 1.6 more biomass relative to the control without microalgae. Moreover, 55% less external oxygen supply was needed to maintain the methane oxidation, as oxygen was produced in situ by the microalgae. An overall methane oxidation rate of 171 ± 27 mg CH₄ L⁻¹ liquid phase d⁻¹ was accomplished in a semi-batch setup, while the excess CO₂ production was lower than 1 mg CO₂ L⁻¹ d⁻¹. Both nitrate and ammonium were feasible nitrogen sources for the methalgae. These results show that a coculture of microalgae and methane oxidizing communities can be used to oxidize dissolved methane under O₂-limiting conditions, which could lead to a novel treatment for dissolved methane in anaerobic effluents.