Extended Aeration System

This paper summarises the results and outcomes of the first Australian wastewater treatment plant (WWTP) energy use benchmarking study conducted on behalf of the Water Services
Association of Australia (WSAA) in the period 2013-14. Data for 142 no. WWTPs from seventeen water utilities spread across seven states and territories in Australia were included. The approach to energy benchmarking selected by WSAA for this study referenced methodology developed and applied for
WWTPs in several European countries over the last two decades, including (amongst others) Switzerland, Germany, and Austria. In particular, recommendations were followed on benchmarking current best practice from published manuals,
research reports and reviews from Germany as well as the Water Environment Research Foundation (USA), and its recent application by SA Water (South Australia).

The purpose of the paper is to demonstrate that the use of fine bubbles generators which are moving into the water is more efficient than the use of fixed fine bubbles generators. The results of the theoretical and experimental researches on the oxygen transfer rate to water are presented in the case of an immobile fine bubbles generator. Keywords—Water; aeration; generating air bubbles; fine bubble generators; oxygen transfer rate; I. INTRODUCTION Oxygen transfer to water, which occurs both in aquariums, fish breeders and sewage, is an important problem in applying aeration technologies. If fine bubbles aeration [1] is used, significant energy savings are obtained, 20 ÷ 50% of the energy required for aeration [2]. Of the power consumption of a sewage plant, 67% is the energy consumption of water treatment [1] [2]. Reducing energy consumption can be done by using fine bubbles generators (FBG) where the pressure loss is low; at the same time, the efficiency of the oxygen transfer to water must be higher and the consumption of compressed air should be reduced. Air pressure at the entrance to the fine bubbles generator is a very important parameter in the selection and monitoring of fine bubbles generators, regardless of the shape or material from which they are built. It is necessary to monitor this parameter during the operation of the aeration system as it indicates the operation state of the fine bubbles generator by the fact that any clogging of the FBG orifices automatically leads to an increase in air pressure at the entrance. The size and the orifices dimensions is a major parameter of FBG, because it directly affects the working pressure of it. The working pressure of the FBG is the air pressure under the orifices plate. Using FBG which moves in water, i.e. mobile FBG has the following advantage: the trajectory of the air bubbles in water is a curve directed toward the free surface of the water; as a result the contact time between the air bubble and the water is higher, the rate of increase in the dissolved oxygen concentration in the water will be higher. As a result, the time required to aerate the water is reduced.

Inadequate wastewater treatment facilities and a general lack of data on hygienic aspects of treated wastewater have hampered the successful implementation of effluent reuse schemes at the national level; in addition, illegal irrigation practices with partially treated effluent impose serious health hazards and environmental problems. The main objective of this research is to investigate the pathogens removal in Upflow Anaerobic Sludge Blanket (UASB)‐septic tanks and Al-Bireh wastewater treatment plant (AWWTP). The UASB‐septic tanks, located at AWWTP, were fed continuously with raw municipal wastewater from the aerated grit chamber of AWWTP. The two pilot scale UASB‐septic tanks (R1 and R2) were operated at two different hydraulic retention times (HRT) of 2 and 4 days for R1 and R2, respectively. At AWWTP, as an extended aeration system with aerobic sludge stabilization, the HRT was about one day. Both raw wastewater and treated effluent were tested for microbial pathogens, including indicator bacteria, protozoa and trophozoite using microscopic and specific culture media. The removal efficacies of R1 and R2 were 15.5% and 15% for fecal coliform and 6.9% and 11% for fecal streptococcus, respectively, while the removal efficacy of the oxidation ditch was 38% for fecal coliform and 16% for fecal streptococcus. Though Salmonellae was detected in 30% of analyzed influent samples, it was not detected in any sample of the effluent of both treatment systems. Also, the treated effluent of R1, R2 and oxidation ditch was parasite‐ (cysts or trophoziote) free. This information can assist municipalities and village councils in the implementation of rational and efficient treatment strategies for sustainable effluent reuse. Finally, the installation of post treatment stages, including filtration and disinfecting units, is recommended in order to comply with prescribed national guidelines for effluent reuse.

Activated sludge foaming, a worldwide problem, usually consists of filamentous bacteria occurring predominantly in the mixed liquor. Because of a lack of pure cultures of most filamentous bacteria and the limited amount of characterisation data, molecular approaches were used to investigate dominant filamentous bacterial strains associated with foaming in Al BirehWastewater Treatment Plant in Palestine. Applying denaturing gradient gel electrophoresis (DGGE), 16S rRNA cloning and sequencing showed the dominance of several filamentous bacteria including Microthrix parvicella, Nocardia sp., Hyphomicrobium facilis, Chloroflexi, Candidates TM7 and Nocardioides oleivorans.