Nitrogen recovery in an integrated system for wastewater treatment and tilapia production

Abstract

An integrated system, consisting of Up-flow Anaerobic Sludge Blanket (UASB)-duckweed-tilapia ponds was used for recovery of sewage nutrients and water recycling. A UASB reactor with 40 liter working volume was used as pre-treatment unit followed by a series of three duckweed ponds for nitrogen recovery. The treated effluent and duckweed biomass was used to feed fishponds stocked with Nile tilapia (Oreochromis niloticus). The UASB reactor was fed with raw, domestic sewage at 6 h hydraulic retention time. The three duckweed ponds were stocked with Lemna gibba and fed with UASB effluent at 15 days hydraulic retention time. Nitrogen recovery from UASB effluent via duckweed biomass represented 81% of total nitrogen removal and 46.5% from the total nitrogen input to the system. In subsequent fishponds the nitrogen recovery from duckweed as fish feed was in the range of 13.4-20%. This nitrogen in fish biomass represented 10.6-11.5 g N from the total nitrogen in the raw sewage fed to the UASB reactor. The growth performance of tilapia (Oreochromis niloticus) showed specific growth rates (SGR) in the range of 0.53-0.97. The range of feed conversion ratio (FCR) and protein efficiency ratio (PER) were 1.2-2.2 and 2.1-2.28, respectively. The results of the experiments showed total fish yield and net fish yield in the range of 17-22.8 ton/ha/y and 11.8-15.7 ton/ha/y respectively. In conclusion UASB-duckweed-tilapia ponds provide marketable by-products in the form of duckweed and fish protein, which represent a cost recovery for sewage treatment.

Use of planted biofilters in integrated recirculating aquaculture-hydroponics systems in the Mekong Delta, Vietnam

“…Actually, a better growth rate (1.56% day −1 ) and a lower FCR (1.4 ± 0.4) was observed in the present study than generally reported in other studies (Cruz & Ridha ; Ridha & Cruz ; El‐Shafai et al . ).…”

“…However, to avoid accumulation of toxic concentrations of ammonia and nitrite in the water, it is necessary to integrate water treatment systems into recirculating aquaculture systems, such as various physical and biological filter systems (Ridha & Cruz ; Shnel et al . ; Davidson & Summerfelt ; El‐Shafai, El‐Gohary, Nasr, Steen & Gijzen ). The excess nutrients and organic matter produced in the recirculating aquaculture system can also be processed in ‛natural' ecosystems such as constructed wetlands (Lin, Jing & Lee ; Konnerup, Trang & Brix ), but these have relatively large footprints and do not grant any income for the farmer.…”

Phytoremediation by Echinodorus palaefolius to Reduce Nitrogen and Phosphate Waste of Intensive Culture Anguilla bicolor in Recirculation Aquaculture Systems

“…The application of Lemna gibba in a recirculation system decreased the feed conversion, increased protein efficiency ratio, and growth performance of Nile tilapia [28], [29]. Feed conversion in aquaculture industry profoundly needs certain consideration because it affects production cost directly.…”

Nutrient Flow in an Integrated Rabbit–Fish–Rice System in Rwanda

“…It is known that when nutrients from feeds are directly used by fish, the recovery rate is higher than when fertilisers are used (Table 4). Tacon et al (1995) in [44], found that supplementing feed in semi-intensive aquaculture farms improved N recovery, ranging from 5% to 25%, in fish. From Table 4, it can be argued that rabbit droppings must be better used by fish ponds than many other inputs to ensure a better environment for Nile tilapia growth.…”