Algal-bacterial System Research Articles

Options for the Rational Design and Operation of Oxidation Ponds

Oxidation ponds can degrade wastewaters at low cost and provide a useful biomass if rational design, operation, and sludge removal practices are carried out. Here, the design of a plug flow Algal Bacterial Clay Treatment System (ABCT) is presented on the bases of both incident sunlight and incoming BOD concentration. Results of kinetic experimental studies are presented in order to determine both optimal and limiting operational parameters. From these experiments, it appeared to be critical to limit pH diurnal variations for effective operation of the treatment system. Empirical computer models were developed to predict reactor parameter variations due to diurnal effects. A computer model based on continuous oxidation reduction potential (redox) measurements appeared to be most useful for automated computer control of variations due to diurnal effects. Chemical addition of CaCl2 facilitated algal biomass flocculation in order to prepare liquid effluents for plant discharge and to prepare biomass for possible beneficial use.

Predictions of Diurnal Fluctuations in an Algal Bacterial Clay Wastewater Treatment System

Carberry's proposed algal bacterial clay treatment (ABCT) process would generate an algal biomass, useful as a food source. This study examined the diurnal fluctuations resulting from alternating light-dark periods and the magnitude of resulting O2, CO2, and pH oscillations. The magnitude of these oscillations was studied under controlled conditions, in order to determine acceptable limits of these fluctuations. The effects of progressive drifts for these parameter values under uncontrolled conditions was also studied in order to determine the rate of decreasing wastewater bacterial biodegradation efficiency and rate of deterioration of algal biomass viability. Experiments were conducted in which algae, bacteria, and substrate were combined at various concentrations in a biostat. Dissolved gas concentrations and pH were continuously recorded; biomass and substrate concentrations were determined over time by periodic sampling. A 12-hour light/dark cycle simulated the natural diurnal light variation. Based on results from these runs, two computer programs were developed to predict the changes in these parameters over a 24-hour period. One model, incorporating redox potential, appeared to be more sensitive to changes in the aqueous environment than the model based on COD. pH values of less that 5 were found to cause system failure due to a continuing decrease in algal concentration. No critical levels were found for either O2 or CO2 although the duration of time spent at a dissolved oxygen concentration of zero depended on initial algal concentration.

Algal-Bacterial Ponding Systems for Municipal Wastewater Treatment in Arid Regions

A pilot plant was constructed to investigate the use of algal-bacterial systems to treat municipal wastewaters in arid regions. The pilot plant consists of sand and oil traps, weir tanks, two facultative ponds (250 m3 holding capacity each), two high-rate ponds (25 m3 holding capacity each), four sedimentation tanks, a sludge digestor, and such auxiliary facilities as a pumping station for wastewater supply, drainage systems, and a site laboratory. The main objectives of the study are to determine the design parameters needed for large-scale algal-bacterial ponds in hot climates and to determine the degree of treatment and disinfection attained in the system by operating the pilot plant. After the algae is separated from the treated water, the final effluent will be used for irrigation, and algae will be used as a soil conditioner. Investigations during start-up, test runs and experiments completed so far focused on the growth of algae and removal of biochemical oxygen demand, chemical oxygen demand, and suspended solids. During the 20-month experimental program, various operating patterns, including series operation of facultative and high-rate ponds, will be investigated. Results obtained so far indicate significant reductions in pollution concentrations.

Development and Application of an Energy Utilization System for Organic Wastewater

The main characteristic of an energy utilization system for organic wastewater is the combination of treatment structures with oxidation ponds, thus compensating for their deficiencies. Depending on the different environmental and economic conditions, various types of treatment can be used and can work well. The main features of the system are as follows: 1. alteration of the microbial phase by using high-energy aquatic plants in place of algal-bacterial systems; 2. Reduction of the problem of pond size by: including the ponds as part of urban afforestation areas; increasing the capacity of treatment sites by designing the ponds as a tower or steps; if land is limited, using pretreat-ment to reduce the size of ponds; 3. the utilization of solar energy to carry out the energy conversion of chemical exergy, avoiding the conversion of exergy into anergy. The energy consumption can be minimized and the problem of aquatic plants in the ponds during winter can be partially solved.

Mass production of freshwater rotifers on liquid wastes: II. Mass production of Brachionus rubens Ehrenberg 1838 in the effluent of high-rate algal ponds used for the treatment of piggery waste

Diluted pig manure was treated in an algal-bacterial system in outdoor algal ponds. The pond effluent was fed once or twice daily to an indoor 501 rotifer culture. Depending on the algal-bacterial biomass concentration in the pond effluent, rotifer cultures containing 200–580 animals per ml could be obtained. Biological, physical and chemical data on the algal pond and the rotifer culture effluent were recorded.

Luxury uptake of nitrogen in flocculating algal-bacterial system

Nitrogen uptake in the range of 8–10% by the algae and bacteria is usually reported in the literature. In the present study algae and bacteria aerated in the presence of a carbon source and added nitrogen took up about 16% of nitrogen.

Kinetics of Chlorine Disinfection in an Ecosystem

Chlorination is one method of achieving dependable disinfection of waste pond effluents, but the presence of unicellular green algae in such effluents makes effective chlorination complex. The kinetics of chlorine disinfection in algal-bacterial systems are investigated in both pure cultures and mixed cultures from samples of actual waste stabilization pond effluents. The parameters studied are coliform bacterial concentration, chlorine dosage, time, algal concentration and type of algae. Based on the results, chlorine disinfection can be achieved under controlled conditions whereby indicator coliform bacterial organisms may be destroyed, leaving most algae essentially intact. However, indiscriminate chlorination of such effluents, which frequently contain large quantities of algae, results in the degradation of algae. When disposed in receiving waters, this could lead to unsuitable conditions for fish life, recreation and water supply.