SummaryA source of high-quality protein for animal feed. based upon algae recovered in the process of upgrading waste oxidation pond effluents and promising to be particularly economical. is being developed at the Technion. Unlike other types of single cell protein (SCP), the algal protein does not have to return the full production cost but only that of concentration and final processing. The balance is shared by the value of waste disposal and the reclaimed water. Whereas such systems as activated sludge require considerable mechanical energy to supply the oxygen needed for aerobically degrading organics in wastewater. oxidation ponds utilize solar energy for that purpose. The sludge obtained when their effluents are clarified consists largely of algae. bacteria, fungi. and zooplankton in relative proportions varying with operating conditions, and contains 40-60% (dry basis) high-quality protein. The highrate oxidation pond (a particularly intensive type of pond) produces on the average 34 g/m*/day solids, or over 100 tons/ha (hectare) annually. Two clarification routes have been found promising: centrifugation and alum flocculation followed by frothflotation. The latter route is less expensive in terms of both fixed and operating cost, and gives clarified effluent of higher quality. which can be seasonally stored with minimal eutrophication because the aluminum removes most of the phosphate from the effluent. A good product has been obtained by drum-drying the concentrate. and preliminary feeding tests have indicated that it can replace at least '4 of the soymeal in broiler rations and ?4 of the fishmeal in carp feed. N o ill effect of the aluminum in the product recovered by alum flocculation has been found so far, but a process for removing and recycling the aluminum has been developed nonetheless. in case ill effects do show up in further tests. The combined value of the benefits derived from a system centered around the high-rate oxidation pond with clarification by flocculation-flotation. in terms of waste treatment by alternative means. potable water saved. and soymeal replaced, significantly exceeds estimated cost.

Algae, bacteria, and zooplankton were counted in samples drawn from 120-and 150-m2 high-rate algae ponds (those used for wastewater treatment). The fraction of nondegraded organic matter was estinated by comparing the ratio of biological and chemical oxygen demands and the bacterial, algal, and zooplankton counts to volatile suspended solids. With pond effluent quality at an acceptable level (around 18 mg of dissolved biological oxygen demand), the algae/bacteria ratio was around 1:100 or even higher, the zooplankton count was negligible, and the bacterial concentration was approximately 1011 cells per liter by direct count. The data for bacteria exceeded those of earlier studies by one to three orders of magnitude.

SummaryDuring the course of operating high-rate algae ponds (HRAP) for wastewater treatment and protein production, changes were found in the two main algae species. The observed changes were interpreted to be a reflection of the operation regime and loading combined with environmental conditions. To verify that these changes were phenotypic and not genetic, experiments were conducted on Scenedesmus dimorphus growing in miniponds ( I 10 L) as well as in the laboratory. The results showed that the changes in S. dimorphus were external and due to the changes in the loading and operating conditions of the ponds adjusted to changing environmental conditions. It was found that wastewater treatment efficiency and algal yield are also correlated with the S. dimorphus type.

Summary

In the past as well as today there have been two conflicting opinions as to whether changes in the algal species in water bodies indicate polymorphism or the development of separate species. Similar changes were also found in High Rade Algae Pond (HRAP) used for wastewater treatment, effluent reclamation and protein production. To critically examine both opinions, samples of HRAP effluent were taken and the algal species identified and measured continuously, using conventional methods.Two main algal species were identified. These remained stable during all four monitoring sessions over a three-year period. The external changes observed in the algae were a reflection of controlled periods of organic loading and the conditions under which the pond was operated, such as retention time (a dependent of radiation), ambient temperature, effluent depth and aeration methods.