Strategies for Controlling Filamentous Bulking in Activated Sludge Wastewater Treatment Plants: The Old and the New

Abstract

Filamentous bulking and foaming are the most common settling problems experienced in activated sludge (AS) wastewater treatment plants (WWTPs). The quality of the final effluent is poor during episodes of bulking and foaming, which is an environmental, human health and economic burden. Remedial measures are often ineffective, and traditional non-specific methods such as chlorination may also negatively impact important functional bacterial species such as nitrifiers. Modifications to older methods as well as new strategies are required for controlling filamentous bulking. Laboratory testing needs to be followed by testing at scale in WWTPs. This review describes the filamentous bacteria responsible for filamentous bulking, with a focus on their global distribution and known factors which are selective for the growth of specific filaments. Traditional and new non-specific and biological control strategies are reviewed and discussed. Research gaps are identified with the aim of promoting continued efforts to establish effective control strategies for filamentous sludge bulking.

Effect of organic loading rates on the performance of membrane bioreactor for wastewater treatment behaviours, fouling, and economic cost

“…Therefore, for an ideal working MBR system, the growth of floc-forming bacteria and filamentous bacteria should coexist in harmony 46 . However, the presence of several physicochemical parameters and/or modifications in process conditions that indirectly affect the chemical status of the activated sludge stimulates the excessive growth of filamentous bacteria 47 , 48 . Depending on the type of filamentous bacteria present, filamentous overgrowth may produce either inter-floc bridging or open flocs.…”

“…While the second kind develops when many filaments grow inside weakly consolidated flocs, thereby trapping water within the flocs (referred to by the green arrows in the Fig. 7 e and f) 47 . In light of this, the proliferation of filamentous bacteria can cause an increase in the viscosity and hydrophobicity of the sludge, which can result in the formation of various foulants and membrane fouling, as seen in the MBR system with an OLR of 3.7 kg COD/m 3 d. Contrarily, no filaments were found when MBR was run at OLR 0.86 and 1.8 kg COD/m 3 d, providing yet more evident proof of the cause of the performance disparity between the three operating systems and the impact of OLR on the membrane fouling.…”

Treatment and Handling of Hydraulic Shock Load of Urea Fertilizer Wastewater in Sequencing Batch Reactor

“…The average DO parameter is 7.48 mg/L which meets the oxygen needs of aerobic microorganisms. The next parameter is temperature, where the average reactor temperature is 25.16°C, which fulfills the aerobic treatment criteria [4].…”

“…The wastewater treatment process with an activated sludge system also often has bulking problems, so flotation is used in sedimentation to separate the sludge from the treated effluent in order to solve this problem. However, this causes high costs and more complex installation operations [4].…”

Bulking of activated sludge in the biological treatment of municipal and industrial wastewater, due to the massive development of filamentous bacteria Type 021N

“…Bulking of activated sludge is a violation of the process of separation of activated sludge from purified wastewater. This is due to the intensive development of filamentous microorganisms, which causes the losses of sludge its ability to sedimentation [1][2][3][4][5]. The development of such type of activated sludge leads to a decrease in the volume of excess sludge water, a deterioration in the density and water yield of the sludge, an increase in the content of suspended substances in purified water, removal of sludge particles together with purified water, and a decrease in the concentration of activated sludge in the recirculation flow until it is completely removed from the system [6][7][8].…”