Effect of water velocity on ammonium and nitrite removal in pilot scale fixed bed biofilters

Mang'era Samwel Mnyoro, Erik Arvin, Renalda N. Munubi, Sebastian W. Chenyambuga, Lars-Flemming Pedersen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The effect of water velocity on nitrification rates in fixed bed biofilters was investigated in three freshwater pilot scale RAS with rainbow trout. Removal of total ammonia nitrogen (TAN) and nitrite-nitrogen were assessed by NH4Cl spikes and tested at four different water velocities in the biofilters (1.4, 5.4, 10.8 and 16.2 m h-1) under identical conditions. Water velocities below 10.8 m h-1 significantly reduced TAN- and nitrite removal rates. The surface specific TAN removal rates correlated with the TAN concentrations at the water velocities 10.8 and 16.2 m h-1, and the first order surface removal rate constant was estimated at 0.45 m h-1. However, no correlations between TAN removal and TAN concentrations were found at the lowest velocities. Up to five-fold elevated nitrite levels were found in the RAS when biofilters were operated at 1.4 m h-1 compared to the trials at other water velocities, substantiating the significant effect of water velocity on both nitrification processes. The importance of biofilter hydraulics documented in this pilot scale RAS probably have implications for design and operation in larger scale RAS.
Original languageEnglish
Article number102160
JournalAquacultural Engineering
Volume93
Number of pages5
ISSN0144-8609
DOIs
Publication statusPublished - 2021

Keywords

  • Nitrification
  • biofiltration,
  • water velocity
  • hydraulics

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