The velocity of wastewater within ditch is 1 to 2ft/s. This process may be adaptable to fluctuations in flows and loadings associated with recreation area wastewater production.

Objectionable odours are formed when rate of oxygen consumption is more in lower levels of lagoon than rate of oxygen transfer from lagoon surface.

The minimum depth considered for an aerated lagoon is 2.5 m. This is considered as 2.5 m even for an aerated lagoon carried out facultatively. Also for aerated lagoons with solid recycling, this is considered as 2.5 m only.

This helps to mix incoming Influent and returned activated sludge (RAS), beginning biological digestion process before liquor enters main part of tank.

The agitation set up by air in aerobic process causes biofilm carrier movement, while in anoxic and anaerobic processes a mixer (normally a horizontal shaft mounted banana mixer) keeps carrier moving.

In moving bed bioreactors catalyst is easy to regenerate, handling cost of a catalyst is low and has plug flow characteristics with good selectivity.

Charged surfaces on media are biologically regenerated as ammonium ions which are adsorbed and n subsequently nitrified by biofilm and desorbed. These reactive surfaces increase treatment efficiency and buffer biofilm communities against toxic compounds in wastewater.

As oxygen is introduced by mechanical units, ponds can function in norrn climates. The increased aeration facilitates increased degradation and pathogen removal.

The combined BOD and nitrogen removal for moving bed bioreactor is 2-2.75 Kg BOD/m³day. The Moving bed bioreactor removes BOD also. These are provided with diffusers in order to provide aeration.

In moving bed reactor, flow of solids is not easy to maintain and solid distribution is also difficult. It consists of poor heat transfer characteristics. The fluid reactant may bypass catalyst bed.