Effects of water quality on algae growth potential

Abstract

Chlamydomonas reinhardtii, a green algae, and Anacystis nidulans, a blue-green algae were used to determine the algae growth potential of wastewater after having received various degrees of treatment. Pure cultures of algae were inoculated into sterile samples of stream water obtained both upstream and downstream from a sewage treatment plant discharge and, also, into sterile samples of raw sewage, primary treated sewage, and secondary treated sewage. Algae growth was measured by a photometric technique and a chlorophyll extract technique. Algae growth was observed to be best in raw sewage. The algae grew better in primary treated waste than in secondary treated waste only in samples where the ammonia nitrogen concentration was not toxic. Upstream water samples supported algae growth until essential nutrients became exhausted. Lag periods were observed in some samples due to the time required for the form of the nutrient to change so it could be used by the algae, e. g., some samples contained sufficient total phosphate, but time for hydrolysis from polyphosphate forms to orthophosphate was necessary for good growth. The ammonia nitrogen concentration in separate secondary treated waste samples was increased in increments by the addition of ammonium hydroxide. Algae growth was stimulated by small additions of nitrogen, but this stimulation decreased with increasing concentrations until toxic effects were observed.