Efficacy of using harmless Bacillus endospores to estimate the inactivation of Cryptosporidium parvum oocysts in water.

The need to use complex in vitro cell culture, expensive equipment, and highly-trained technicians that are available only to specialist laboratories has significantly limited studies assessing the potential of pulsed UV light (PUV) to inactivate the waterborne parasite Cryptosporidium parvum in drinking water. This constitutes the first study to report on the use of different non-pathogenic Bacillus endospores as potential surrogate organisms to indicate the PUV inactivation performance of a C. parvum oocyst suspended in water. Findings showed that PUV effectively inactivated approximately 5 log10 CFU/ml Bacillus megaterium and Bacillus pumilus endospores suspended in water at a UV dose of 9.72 µJ/cm(2) that also inactivated statistically similar levels of C. parvum oocysts (P < 0.05), as determined by combined in vitro HCT-8 cell culture and quantitative PCR. Specifically, this study demonstrated that B. megaterium exhibited greater or similar PUV-inactivation kinetic data compared to that of similarly treated C. parvum over the UV dose range 6.4 to 12.9 µJ/cm(2). Therefore, the former may be used as an indicator organism for safely investigating the PUV-inactivation performance of this chlorine-resistant, waterborne parasite at the waste-water treatment plant level. Findings presented will impact positively on future water quality studies and on public health.

Small-scale domestic wastewater treatment using an alternating pumped sequencing batch biofilm reactor system.

An alternating pumped sequencing batch biofilm reactor (APSBBR) system was developed to treat small-scale domestic wastewater. This laboratory system had two reactor tanks, Reactor 1 and Reactor 2, with two identical plastic biofilm modules in each reactor. Reactor 1 of the APSBBR had five operational phases--fill, anoxic, aerobic, settle and draw. In the aerobic phase, the wastewater was circulated between the two reactor tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by microorganisms in the biofilms when they were exposed to the air. This paper details the performance of the APSBBR system in treating synthetic domestic wastewater over 18 months. The effluent from the APSBBR system satisfied the European Wastewater Treatment Directive requirements, with respect to COD, ammonium-nitrogen and suspended solids. The biofilm growth in the two reactor tanks was different due to the difference in substrate loadings and growth conditions.

Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR).

A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .