Long-term operation of a novel pilot-scale six tanks alternately operating activated sludge process in treating domestic wastewater

Abstract

The performance of a new pilot-scale six tanks activated sludge process has been evaluated for 303 d, receiving real domestic wastewater with a flow rate of 15-24.4 L/h. Partial nitrification via nitrite and microbial community structure were investigated in this system. The result shows that the nitrite accumulation rate was achieved successfully over 94% in the last aerobic compartment through a combination of short hydraulic retention time and low dissolved oxygen (DO) level. Fluorescence in situ hybridization analysis was used to correlate ammonia-oxidizing bacteria (AOB) numbers with nutrient removal via nitrite. It was shown that in response to complete and partial nitrification modes, the numbers of AOB population were 7.7 x 10(7) cells/g mixed liquor suspended solids (MLSS) and 5.31 x 10(8) cells/g MLSS, respectively. The morphology of the sludge indicated that there is a small rod-shaped and spherical cluster which was mainly dominantly bacterial according to scanning electron microscope. Higher pollutant removal efficiencies of 86.2%, 98%, and 96.1%, for total nitrogen, NH4+ - N, and total phosphorus, respectively, were achieved by a long-term operation of the six tanks activated sludge process at a low DO concentration and low chemical oxygen demand to nitrogen ratio which were approximately equal to the complete nitrification-ldenitrification with the addition of an external carbon source at a concentration of 1.5-2.5 mg/L.

Variations of morphology of activated sludge flocs studied at full-scale wastewater treatment plants

“…The effectiveness of solid-liquid separation and, as a consequence, the quality of the treated effluent depends on the morphology of activated sludge flocs. [1,2] Morphological parameters of the activated sludge flocs can be divided into two categories: (1) parameters describing floc size and (2) parameters describing flocs shape. The following parameters belong, inter alia, to the first category: projected area, equivalent diameter and perimeter.…”

Microaerophilic Activated Sludge System for Ammonia Retention toward Recovery from High-Strength Nitrogenous Wastewater: Performance and Microbial Communities

“…Based on their physiological properties, the MAS system eliminates these ammonia-oxidizing microorganisms (AOMs). AOMs have much lower specific growth rates (μ max [h –1 ]) (0.028–0.085 h –1 for AOB; 0.010–0.013 h –1 for AOA; 0.019–0.060 h –1 for NOB, and 0.006 h –1 for comammox Nitrospira ) and oxygen affinities (oxygen half-saturation coefficients K O [μM]) (1–40 μM for AOB, 2–4 μM for AOA, and 4.06–16.88 μM for NOB) than those of heterotrophic bacteria (typical μ max of 0.25 h –1 and K O of 0.00312 μM). , These distinctive biokinetic properties should allow the suppression of AOMs growth but sustain heterotrophic bacteria growth by controlling operational parameters (e.g., shorter solids retention time [SRT] and lower dissolved oxygen [DO] concentration). However, this hypothesis requires experimental verification.…”

Microaerophilic activated sludge system for ammonia recovery from high-strength nitrogenous wastewater: Performance and microbial communities

“…15, 16 These distinctive biokinetic properties should allow the suppression of AOMs growth but sustain heterotrophic bacteria growth by controlling operational parameters ( e . g ., shorter solid retention time [SRT] and lower dissolved oxygen [DO] concentration 17 ). However, this hypothesis requires experimental verification.…”

“…AOMs have much lower specific growth rates (µmax [h −1 ]) (0.028-0.085 h −1 for AOB; 0.010-0.013 h −1 for AOA; 0.019-0.060 h −1 for NOB, and 0.006 h −1 for comammox Nitrospira) 14 and oxygen affinities (oxygen half-saturation coefficients KO [mM]) (1-40 mM for AOB, 2-4 mM for AOA, and 4.06-16.88 mM for NOB) 14 than those of heterotrophic bacteria (typical µmax of 0.25 h −1 and KO of 0.00312 mM). 15,16 These distinctive biokinetic properties should allow the suppression of AOMs growth but sustain heterotrophic bacteria growth by controlling operational parameters (e.g., shorter solid retention time [SRT] and lower dissolved oxygen [DO] concentration 17 ). However, this hypothesis requires experimental verification.…”