Immobilized periphytic cyanobacteria for removal of nitrogenous compounds and phosphorus from shrimp farm wastewater

Cyanobacteria can be used to remove nitrogenous compounds from wastewater, but a major bottleneck in the process is the separation of cyanobacterial biomass from the treated water discharge, which may cause eutrophication. The current study assessed the suitability of three periphytic cyanobacteria (Geitlerinema sp., Gloeotrichia sp., and Lyngbya sp.) isolated from shrimp ponds. These cyanobacteria were immobilized by self-adhesion to polyvinyl chloride sheets, forming mats, and were screened for their efficacy to reduce nitrogenous compounds and phosphorus. Among the three isolates, Geitlerinema sp. showed the highest reduction rate (98%) and was further tested using shrimp pond wastewater. The results showed that initial wastewater concentrations (mg L-1) of total ammonia nitrogen (5.0), nitrite nitrogen (2.9), and soluble reactive phosphorus (2.5) were significantly (P < 0.05) reduced within 7 days in tanks containing wastewater + Geitlerinema sp. mats (0.1, 0.2, and 0.8) compared to wastewater + substrate only (4.3, 2.7, and 2.3) or wastewater only (4.4, 2.8, and 2.4). In addition, Geitlerinema sp. was found to be nontoxic to Artemia. Fast and effective sequestration of nutrients from wastewater by the Geitlerinema mats, as well as ease of harvesting from the mats, make this treatment an attractive alternative for wastewater treatment.