Leachate treatment and greenhouse gas emission in subsurface horizontal flow constructed wetland.

Organic and nitrogen removal efficiencies in subsurface horizontal flow wetland system (HSF) with cattail (Typha augustifolia) treating young and partially stabilized solid waste leachate were investigated. Hydraulic loading rate (HLR) in the system was varied at 0.01, 0.028 and 0.056 m(3)/m(2) d which is equivalent to hydraulic retention time (HRT) of 28, 10 and 5 d. Average BOD removals in the system were 98% and 71% when applied to young and partially stabilized leachate at HLR of 0.01 m(3)/m(2) d. In term of total kjeldahl nitrogen, average removal efficiencies were 43% and 46%. High nitrogen in the stabilized leachate adversely affected the treatment performance and vegetation in the system. Nitrogen transforming bacteria were found varied along the treatment pathway. Methane emission rate was found to be highest at the inlet zone during young leachate treatment at 79-712 mg/m(2) d whereas CO2 emission ranged from 26-3266 mg/m(2) d. The emission of N2O was not detected.

Particle and microorganism removal in floating plastic media coupled with microfiltration membrane for surface water treatment.

Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtration rates of 5, 10 and 15 m3/m2 x h. Treated water was then fed into a microfiltration unit where different filtration rates were examined at 0.6, 1.0 and 1.4 m3/m2 x d. It was found that polyaluminum chloride was the best coagulant for the removal of particle, algae and coliform bacteria. Average turbidity in treated water from the floating plastic media filter was 3.3, 12.2 and 15.5 NTU for raw water of 80 NTU and 12.9, 11.7 and 31.2 NTU for raw water of 160 NTU after 6 hours at the filtration rates of 5, 10 and 15 m3/m2 x h, respectively. The microfiltration unit could further reduce the turbidity to 0.2-0.5 NTU with low transmembrane pressure development of 0.3-3.7 kPa. Microfiltration membrane could retain most of algae and coliform bacteria remaining in the effluent from the pretreatment unit. It was found that at higher turbidity, algae and coliform bacteria removal efficiencies were achieved at lower filtration rate of the system of 5 m3/m2 x h whereas a higher filtration rate of 15 m3/m2 x h yielded better coliphage removal.