Sludge reduction potential of the activated sludge process by integrating an oligochaete reactor

Abstract

a b s t r a c tAn oligochaete reactor linked to an integrated oxidation ditch with vertical cycle (IODVC) was used to investigate the sludge reduction potential induced by worms. The presence of Tubificidae was observed in the worm reactor throughout the operational period after its inoculation, and Tubificidae was occasionally found in the IODVC. Free-swimming worms, Aeolosoma hemprichi, Nais elinguis, and Aulophorus furcatus, were found in both the IODVC and the worm reactor, but A. hemprichi was dominant. A. hemprichi reached its maximum, 322 and 339 Aeolosoma/mL mixed liquor on day 49 in the worm reactor and the IODVC, respectively. The presence of oligochaetes or the integration of worm reactor with the IODVC had little effect on sludge yield, but the worm growth was helpful for improving sludge settling characteristics. The average sludge yield and sludge volume index (SVI) in the IODVC were 0.33 kgSS/kgCOD removed and 78 mL/g, respectively. The worm presence had little impact on effluent quality of the IODVC, but it caused phosphorus release into the effluent. The average COD, NH 4 + -N, and SS concentrations in the effluent of the IODVC were 49.06, 12.82, and 58.25 mg/L, respectively. No total nitrogen (TN) release into the effluent of the IODVC occurred.

A comparative study of synchronous treatment of sewage and sludge by two vermifiltrations using an epigeic earthworm Eisenia fetida

“…Concerning on predation on bacteria to minimize sludge reduction in biological wastewater treatment, a variety of researches mainly focus on the predation by protozoa and metozoa in activated sludge system [1,2,6,7], while vermifiltration utilizes a higher and larger oligochaete organism-earthworms in an attached-carrier biofilm reactor to acquire low sludge production. The former reported on the sludge yields of a pilot scale activated sludge system for domestic wastewater treatment ranged from 0.15 to 0.17 kg SS/kgCOD removed at ambient temperature of 18-23 • C, and that of the submerged MBR was in the range of 0.00-0.15 kg SS/kgCOD removed at the temperature of 20 • C [9,17].…”

“…A large amount of excess actived sludge produced in wastewater purification, if not properly disposed, may pose a potential threat to both the environment and the human health because of heavy metals, organic pollutants and pathogen [1]. Sewage sludge treatment and disposal is, therefore, becoming one of the most serious challenges in WWTPs 1 as a result of legal constraints, rising costs and public sensitivity [2].…”

“…An ideal way to solve sludge-associated problems is to reduce sludge production in the wastewater purification process rather than the post-treatment of the sludge generated [5]. There is therefore a growing interest on sludge reduction by predation on bacteria [1,2,6,7], which is based on the ecological principle that during energy transfer from bacteria to higher trophic level organisms (protozoa and metazoa), energy is lost due to inefficient biomass conversion. Thus the predator may make a large contribution to biomass reduction [8].…”

“…Thus the predator may make a large contribution to biomass reduction [8]. The performance of oligochaetes for sludge reduction in biological wastewater treatment has been paid more attentions than that of protozoa for sludge reduction [1,2,6,7,9]. The oligochaetes used for treatment of excess activated sludge can be divided into two groups, firstly, the large aquatic worms such as the Tubificidae, Lumbriculidae and the semi-aquatic or terrestrial Enchytraeidae and, secondly, the small aquatic worms such as Naidids and Aeolosomatids [4].…”

“…The oligochaetes used for treatment of excess activated sludge can be divided into two groups, firstly, the large aquatic worms such as the Tubificidae, Lumbriculidae and the semi-aquatic or terrestrial Enchytraeidae and, secondly, the small aquatic worms such as Naidids and Aeolosomatids [4]. Although the presence of worms especially small aquatic worms in the aerobic wastewater treatment may lead to substantial sludge reduction, the practical application of worms for sludge reduction is still uncontrollable [1,4].…”