Granulation of anaerobic sludge in the sulfate-reducing up-flow sludge bed (SRUSB) of SANI(®) process.

This study reports on anaerobic sludge granulation in a laboratory-scale sulfate-reducing up-flow sludge bed (SRUSB) in a novel sulfate reduction, autotrophic denitrification and nitrification integrated (SANI(®)) process for treatment of saline sewage. Granulation occurred in 30 d and reached full development in 90 d. The sulfate-reducing granules grew up to around 1 mm after 90 d with 21 mL/g SVI5 (sludge volume index measured after 5 min) and the biomass concentration reached 29 g/L after 4 months' operation. The reactor removed 89% chemical oxygen demand (COD) and reduced 75% sulfate within 1 h of hydraulic retention time, under a COD loading rate of up to 6.4 kg COD/(m(3) · d).

Industrial flue gas desulfurization waste may offer an opportunity to facilitate SANI® application for significant sludge minimization in freshwater wastewater treatment.

This paper reports an exploratory study on the use of a sulfite-rich industrial effluent to enable the integration of a sulfite-sulfide-sulfate cycle to the conventional carbon and nitrogen cycles in wastewater treatment to achieve sludge minimization through the non-sludge-producing Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI) process. A laboratory-scale sulfite reduction reactor was set up for treating sulfite-rich synthetic wastewater simulating the wastewater from industrial flue gas desulfurization (FGD) units. The results indicated that the sulfite reduction reactor can be started up within 11 d, which was much faster than that using sulfate. Thiosulfate was found to be the major sulfite reduction intermediate, accounting for about 30% of the total reduced sulfur in the reactor effluent, which may enable additional footprint reduction of the autotrophic denitrification reactor in the SANI process. This study indicated that it was possible to make use of the FGD effluent for applying the FGD-SANI process in treating freshwater-based sewage.

Phosphorus release and uptake during start-up of a covered and non-aerated sequencing batch reactor with separate feeding of VFA and sulfate.

This study explored a sulfur cycle-associated biological phosphorus (P) removal process in a covered and non-aerated sequencing batch reactor (SBR) fed with volatile fatty acid (VFA) and sulfate separately. During the 60-day start-up, both phosphate release and uptake rates increased, while poly-phosphate cyclically increased and decreased accordingly. The P-release and P-uptake rates were associated with VFA uptake and sulfate reduction. The average ratio of potassium to phosphate during the P-uptake and P-release was also determined to be 0.29-0.31 mol K/mol P, which is close to a reported value (0.33) for biological phosphorus removal. All this evidence confirmed there was biological P removal in this reactor, in which metabolism could be different from conventional biological P removal.

Integration of seawater and grey water reuse to maximize alternative water resource for coastal areas: the case of the Hong Kong International Airport.

Development, population growth and climate change have pressurized water stress in the world. Being an urbanized coastal city, Hong Kong has adopted a dual water supply system since the 1950s for seawater toilet flushing for 80% of its 7 million inhabitants. Despite its success in saving 750,000 m(3)/day of freshwater, the saline sewage (consisting of about 20-30% of seawater) appears to have sacrificed the urban water cycle in terms of wastewater reuse and recycling. Can seawater toilet flushing be applied without affecting the urban water cycle with respect to sustainable water resource management? To address this issue, we examined the entire urban water cycle and developed an innovative water resource management system by integrating freshwater, seawater and reclaimed grey water into a sustainable, low-freshwater demand, low-energy consumption, and low-cost triple water supply (TWS) system. The applicability of this novel system has been demonstrated at the Hong Kong International Airport which reduced 52% of its freshwater demand.