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.     

Survival dynamics of fecal bacteria in ponds in agricultural watersheds of the Piedmont and Coastal Plain of Georgia

Animal agriculture in watersheds produces manure bacteria that may contaminate surface waters and put public health at risk. We measured fecal indicator bacteria (commensal Escherichia coli and fecal enterococci) and manure pathogens (Salmonella and E. coli 0157:H7), and physical-chemical parameters in pond inflow, within pond, pond outflow, and pond sediments in three ponds in agricultural watersheds. Bishop Pond with perennial inflow and outflow is located in the Piedmont, and Ponds A and C with ephemeral inflow and outflow in the Coastal Plain of Georgia. Bromide and chloride tracer experiments at Bishop Pond reflected a residence time much greater than that estimated by two models, and indicated that complete mixing within Bishop Pond was never obtained. The long residence time meant that fecal bacteria were exposed to solar UV-radiation and microbial predation. At Bishop Pond outflow concentrations of fecal indicator bacteria were significantly less than inflow concentrations; such was not observed at Ponds A and C. Both Salmonella and E. coli 0157:H7 were measured when concomitant concentrations of commensal E. coli were below the criterion for surface water impairment indicating problems with the effectiveness of indicator organisms. Bishop Pond improved down stream water quality; whereas, Ponds A and C with ephemeral inflow and outflow and possibly greater nutrient concentrations within the two ponds appeared to be less effective in improving down stream water quality.     

Enteric virus survival in algal-bacterial wastewater treatment systems—I : Laboratory studies

The survival of a representative enteric virus, poliovirus type 1, in laboratory models of algal-bacterial sewage treatment systems and the interactions of poliovirus with stabilization pond water was studied. In laboratory reactors a fraction of the total poliovirus present rapidly adsorbed to stabilization pond water solids by a reversible process, conforming to a Freundlich adsorption isotherm. In laboratory cultures the growth of Scenedesmus quadricauda and Bacillus megaterium in sterile sewage had no detrimental effect on poliovirus survival, whereas the growth of heterogeneous populations of stabilization pond bacteria in the same medium resulted in substantial virus inactivation. Appreciable poliovirus inactivation occurred in laboratory cultures of mixed algal-bacterial populations obtained from stabilization ponds. Because the degree of antiviral activity in these cultures was greater than that in cultures of stabilization pond bacteria alone, additional microbial factors must contribute to this virus inactivating phenomenon. The results of this study suggest that in algal-bacterial treatment systems both virus adsorption to solids and virus inactivation due to microbial activity play a role in reducing the enteric virus concentration in wastewater.     

Septage disposal in waste recycling ponds

Experiments were carried out to investigate the feasibility of septic tank sludge (septage) disposal into pilot-scale waste recycling ponds for the production of algae and fish. A septage loading of 100 kg COD ha⁻¹ day⁻¹ to four 4-m² single-stage ponds resulted in the production of algal biomass and dissolved oxygen in the pond water, suitable for Tilapia growth. Some microbiological investigations of this waste recycling scheme were undertaken using ten earth ponds (each with the dimensions of 20 × 10 × 1.3 m: length × width × depth). It was found that the densities of coliform bacteria and bacteriophages in the pond water and sediment tended to increase with increased septage loadings and loading periods. The ponds fed with septage at the loading of 100 kg COD ha⁻¹ day⁻¹ were found to contain higher densities of these microorganisms than those of the control pond without septage feeding. The possible public health impact resulting from this practice was assessed.     

The effect of physical configuration on the performance of laboratory-scale oxidation ponds

This study describes an investigation into the effect of configuration and scale on the performance of oxidation pond systems. Laboratory studies with a synthetic milk wastewater used large and small series systems, and a large single pond. The performance of these systems was investigated using organic loadings in the range of 50–300 kg BOD₅/ha/d and detention times which ranged from 3.25 to 13 days at a temperature of 20°C. The differences between the performance of the three pond systems were analysed and it was shown that there was no significant difference between a series of four ponds and a large pond of equal total area and volume, and also between different scales of pond. The mathematical relationships developed suggest that the performance of the laboratory-scale system was comparable to that of a full-scale system.     

Removal of organic matter in stormwater ponds: a plug-flow model generalisation from waste stabilisation ponds to shallow rivers

ABSTRACT

This study investigates the effect of flow conditions on the organic matter concentration, removal efficiency, and reaction kinetics in a stormwater pond in Fortaleza, Brazil. As a result of unauthorized sewage discharges, BOD and COD concentrations were similar to those of combined sewer systems. The concentrations remained roughly the same during the rainy season, which was attributed to sewage network overflow. Removal efficiencies ranged from 70–90%, similar to primary facultative ponds. Fitting different hydraulic models to the field data, it was possible to obtain BOD and COD removal rates that could be described as functions of the Reynolds number. The best fit was achieved considering the plug-flow assumption, and a general BOD model including data reported in the literature for waste stabilisation ponds, stormwater ponds and shallow rivers was derived. Lastly, simulations with this general model were performed to assess the impact of remediation measures on the studied pond.     

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.     

Fate of pathogens in thermophilic aerobic sludge digestion

The effect of autoheated aerobic thermophilic digestion on the pathogen content of sewage sludges was studied and compared to that of conventional mesophilic anaerobic digestion. Both systems were full scale, continuously-fed facilities operated in parallel and utilized a feed sludge of thickened primary and waste-activated sludge.The relative populations of viruses, Salmonella sp., total and fecal coliforms, fecal streptococci and parasites found before and after digestion were compared. The full scale mesophilic anaerobic digesters were operated at relatively constant conditions, i.e. digester temperature constant at 35°C, and loading rates constant, etc., while the full scale autoheated aerobic digester was operated under a wide range of loading conditions. At all of the conditions studied, the autoheated digester temperature exceeded 45 C. Virus and Salmonella sp. concentrations in the effluent from the aerobic unit were below detectable limits in 10 of 11 samples and 6 of 6 samples, respectively, whereas the anaerobic digester effluent contained detectable numbers of viruses and Salmonella sp. Bacterial indicator counts and parasite concentrations were less in the autoheated digester effluent than in the effluent from the anaerobic digester. It was concluded that the simple autoheated aerobic digestion process could be used to produce a virtually pathogen-free sludge at a cost comparable to that of conventional, mesophilic anaerobic digestion.     

A novel tracer technique for the assessment of fine sediment dynamics in urban water management systems

Urban storm water run off can reduce the quality of receiving waters due to high sediment load and associated sediment-bound contaminants. Consequently, urban water management systems, such as detention ponds, that both modify water quantity through storage and improve water quality through sediment retention are frequently-used best management practices. To manage such systems effectively and to improve their efficiency, there is a need to understand the dynamics (transport and settling) of sediment, and in particular the fine sediment fraction (<63 μm) and its associated contaminants within urban storm water management systems. This can be difficult to achieve, as modelling the transport behaviour of fine-grained and cohesive sediment is problematic and field-based measurements can be costly, time-consuming and unrepresentative.The aim of this study was to test the application of a novel cohesive sediment tracer and to determine fine sediment transport dynamics within a storm water detention pond. The cohesive sediment tracer used was a holmium labelled montmorillonite clay which flocculated and had similar size and settling velocity to the natural pond sediment it was intended to mimic. The tracer demonstrated that fine sediment was deposited across the entire pond, with the presence of reed beds and water depth being important factors for maximising sediment retention. The results of the sediment tracer experiment were in good agreement with those of a mathematical sediment transport model. Here, the deposited sediment tracer was sampled by collecting and analysing surface pond sediments for holmium. However, analysis and sampling of the three dimensional suspended tracer ‘cloud’ may provide more accurate information regarding internal pond sediment dynamics.     

The retardment of algal growth in maturation ponds

During recent times inhibition of planktonic algal growth was found to prevail at Windhoek and other localities both in South West Africa and the Republic of South Africa. The phenomenon has important implications with respect to sewage treatment in ponds, particularly maturation pond systems. Inhibition of algal growth in case of the Windhoek maturation ponds appears to be caused by increased sedimentation of algal cells, by depression of the algal growth rate, or by both.     

Exploring forecast-based management strategies for stormwater detention ponds

Dry detention ponds are commonly implemented to mitigate the impacts of urban runoff on receiving water bodies. They currently rely on static control through a fixed limitation of their maximum outflow rate. This study investigated the performance of several enhanced management strategies for a dry detention pond located at the outlet of a small urban catchment near Québec City, Canada. Among the enhanced scenarios studied are some previously developed real-time control (RTC) strategies, and new operating rules relying on a daily manual adjustment of the outlet gate. Both types of control make use of rainfall forecasts originating from the initial or downscaled Canadian global ensemble prediction system. Different ways of using the forecasts' ensemble spread were considered to take action. The pond performances were investigated considering three different volumetric capacities (including the existing volume). The RTC scenarios are very promising. The value of taking rainfall forecasts into account to prevent pond overflowing is demonstrated. Strategies involving only manual adjustments on a daily basis do not seem helpful.     

Upgrading a facultative pond by implanting water hyacinth

Water hyacinth was implanted in one of two existing facultative ponds and both units were operated in parallel under comparable conditions. The ponds were fed with mainly domestic wastewater after pretreatment in anaerobic ponds and operated at a BOD₅-loading of about 48 kg (ha d)⁻¹ and a detention time of 12 days. This paper covers a period of 4 months, from the implantation of the water hyacinths until no further systematic change in the treatment efficiency of the water hyacinth pond was observed. The median effluent concentrations of the facultative pond for SS, COD, TKN and TP were 55, 95, 6.4 and 1.4 mg l⁻¹, respectively. The values for the water hyacinth pond were 12, 26, 2.5 and 0.4 mg l⁻¹, respectively. The average DO effluent concentration of the water hyacinth pond was 1.2 mg l⁻¹, but this still increased slightly as compared to the influent. The study demonstrates that the implantation of water hyacinth is an appropriate option for upgrading facultative ponds. In many cases where more stringent effluent standards are imposed the method may be a suitable alternative to technical treatment processes.     

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.     

Relationship between nutrient loading and phytoplankton standing crop in outdoor experimental ponds with continuous flow systems

The relationship between nutrient loading and phytoplankton standing crop was studied in outdoor experimental ponds during a period from autumn 1978 to winter 1979. Throughout the experimental period, phosphate, nitrate and ammonium at 3.5, 7.0 and 10.6 mg m⁻² d⁻¹ of phosphorus, respectively were added continuously into three experimental ponds. Nitrogen loading was adjusted to about 7 times the phosphorus by weight. The apparent water residence time of each experimental pond was 20 days.The phytoplankton standing crop at steady state showed a high correlation to the nutrient loading. The relationship between phosphorus loading (P, mg m⁻² d⁻¹) and concentrations of chlorophyll-a (Chl-a, μg l⁻¹) in the experimental ponds could be expressed by the following formula; (Chl-a) = 18.1 (P) − 57 (n = 14, r = 0.90).The relationship between total phosphorus and chlorophyll-a concentrations in the experimental ponds varied in each season. The slopes of the regression lines were greatest in autumn, and smallest in summer.     

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.     

Computational fluid dynamics modelling of different detention pond configurations in the interest of sustainable flow regimes and gravity sedimentation potential

This study presents the results of the flow regime evaluation, by means of computational fluid dynamics (CFD), of a vegetated detention pond located at Waterlooville, Hampshire, UK. Alternative pond layouts were assessed for the same flow conditions on the basis of recommendations made in the literature. The results were validated by comparing the maximum computational velocities for the same case using different numbers of mesh elements. It was found that the development of a CFD model of detention ponds is intricate but feasible. The main findings were: (i) The present design performed well in terms of flood risk management, but the flow patterns could result in questionable treatment efficiency; (ii) vegetation seems to promote horizontal recirculation and turbulence; (iii) triangular and elliptical pond designs showed very poor performance; (iv) the most appropriate design for the given location and hydrological regime is an elliptical pond with a central emergent/submerged island.     

Measurement and three-dimensional simulation of flow in a rectangular detention tank

There are two main ways to obtain better knowledge of the hydraulics of ponds, namely measurements and simulations. In this study, the applicability of using three-dimensional simulations as an engineering tool in stormwater pond design was investigated. To do this, three-dimensional simulations were compared with measurements of flow pattern and residence time in a large physical model of a detention tank (13 × 9 × 1 m). The agreement between measurements and simulations concerning both flow pattern and residence time distribution curves was found to be good for high flow rates.     

Analysis of microbiota in rhizosphere,water and gut of grass carp (Ctenopharyngodon idella) in ponds treated with artificial floating beds

With the increasing demand for environment friendly aquaculture, artificial floating beds have been now widely applied. However, there are few data available on the effect on microbiota in ponds. This study assessed the rhizobacteria community of artificial floating beds with three different kinds of aquatic plants [water spinach (Ipomoea aquatic), water hyacinth (Eichhornia crassipes) and alligator weed (Alternanthera philoxeroides)]. We used Polymerase Chain Reaction‐Denaturing Gradient Gel Electrophoresis to assess whether artificial floating beds would result in changes in microbiota of pond water and gut of grass carp (Ctenopharyngodon idella). The results showed that there existed no significant differences in rhizobacterial composition, and artificial floating beds would not greatly affect the microbiota of pond water. The dominant microbiota in the guts of grass carp changed from Aeromonas jandaei to Paenibacillus sp. Our results indicated that artificial floating beds may serve as a candidate of modulating fish gut microbiota.     

Treatment of stormwater using a detention pond and constructed filters

A stormwater treatment plant, consisting of a detention pond, a constructed filter system and a constructed wetland, has been investigated according to stormwater quality improvement, sediment and heavy metals accumulation and potential toxicity of the stormwater and sediment. The reduction of metal content in the detention pond was on average 26?–?84%. No acute toxicity in the stormwater was detected although heavy metal levels often exceeded guideline values during storm events. Pore water samples of the collected sediments were not toxic but the whole sediment was toxic when assessed with the Microtox^® Solid-phase test. The constructed filter system became clogged due to cementation of the filter substrate.     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—II. Experimental studies on algal interaction

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.