Factors affecting the performance of horizontal flow constructed treatment wetland vegetated with Cyperus papyrus for municipal wastewater treatment

The effect of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a pilot scale subsurface horizontal flow constructed treatment wetland (HFCTW) vegetated with Cyprus papyrus was investigated. Different HLRs were applied to the treatment system namely 0.18, 0.10, and 0.07 m³/m². d with corresponding HRTs of 1.8, 3.2, and 4.7 days, respectively. The flow rate was 8 m³/d, and the average organic loading rate (OLR) was 0.037 kg BOD/m³/d. Results showed that the performance of the HFCTW was linearly affected by decreasing the HLR and increasing the HRT. The highest treatment efficiency was achieved at HRT (4.7 days) and HLR (0.07 m³/m². d). The percentage reductions of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) were 86%, 87%, and 80%, respectively. Satisfactory nutrient removal was obtained. Also, removal of 2–3 logs of bacterial indicators of pollution was achieved. The dry biomass of Cyperus was 7.7 kg/m² and proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area.     

Habitat associations of papyrus specialist birds at three papyrus swamps in western Kenya

Birds of papyrus swamps have not been adequately studied in Kenya, and little is known about their ecology and habitat associations. Using fixed‐radius point counts and playbacks, we counted papyrus specialist birds and evaluated papyrus physical characteristics and levels of disturbance at a series of sample stations at three papyrus swamps of Dunga, Koguta and Kusa in the Kenyan sector of Lake Victoria. Papyrus height and density were significantly correlated across all sites but negatively correlated with levels of disturbance. Standardized point counts of swamp birds showed the papyrus gonolek Laniarius mufumbiri and Carruthers's cisticola Cisticola carruthersi to be the most abundant papyrus specialists across sites. Only Carruthers's cisticola numbers differed between sites. Overall, papyrus cover was the best predictor of the presence and abundance of all papyrus specialist birds, and significantly predicted the numbers of papyrus gonolek and white‐winged warbler Bradypterus carpalis.     

Bio-assay study of response by a parasitoid to frass and feeding substrates of its host, the stalk borer Eldana saccharina

In Petri dish and olfactometer tests Goniozus natalensis Gordh (Hymenoptera: Bethylidae) exhibited a host-searching response upon contact with, and at a short distance from, frass of its natural host, Eldana saccharina Walker (Lepidoptera: Pyralidae), whichever the substrate on which E. saccharina had been feeding. The substrates were two host plants, sugarcane or Cyperus papyrus L.; diet media based respectively on sugarcane, papyrus, or cellulose; or a synthetic diet medium, containing no plant material. Host-searching behaviour increased in intensity with age and after mating of G. natalensis females. Parasitoids responded similarly to frass produced by male and female E. saccharina larvae. The substrates themselves elicited little response in G. natalensis. Frass of another borer, Sesamia calamistis Hamps. (Lepidoptera: Noctuidae), fed on sugarcane-based medium, also elicited little response in G. natalensis. The results suggest that frass of E. saccharina larvae contains a material, evidently volatile, to which their parasitoid G. natalensis responds, irrespective of the substrate on which the E. saccharina subsist.     

Hypoxia Tolerance of Two Haplochromine Cichlids: Swamp Leakage and Potential for Interlacustrine Dispersal

The ability to tolerate hypoxia in some haplochromine cichlid fishes contributes to the richness of habitats occupied by the lineage and may be important in interlacustrine dispersal through swampy channels. Lacustrine members of the genus Astatotilapia tend to be ecologically plastic but are rarely encountered in the interior of dense swamps. A notable exception is seen in the swamp corridor that joins Lake Kabaleka with Lake George, Uganda, where one species (Astatotilapia wrought-iron) is abundant, and a second species, A. aeneocolor, is rare. Both species are abundant in the open waters of the main lake. In this paper, we compare physiological (oxygen consumption) and behavioral indicators of hypoxia tolerance between A. wrought-iron from swamp and open-water habitats and between the two species of Astatotilapia. When exposed to progressive hypoxia, all fish used aquatic surface respiration (ASR); however, swamp-dwelling A. wrought-iron showed lower gill ventilation rates prior to the initiation of ASR, higher pre-ASR aggression rates, higher swimming speed during ASR, and a higher rate of bubble exchange than both the open-water group of A. wrought-iron and A. aeneocolor. These differences may reflect interpopulational variation in selection pressure for low-oxygen tolerance between swamp and open-water habitats. Several lines of evidence suggest that A. wrought-iron was in general more hypoxia tolerant than A. aeneocolor. These include a lower ASR₉₀ threshold, a drop in gill ventilation rate with the onset of ASR, and lower rate of equilibrium loss under extreme hypoxia in A. wrought-iron. The routine metabolic rate and critical oxygen tension did not differ between swamp-dwelling and open-water A. wrought-iron, or between A. wrought-iron and A. aeneocolor. Comparative data on the ASR thresholds and critical oxygen tensions of the Astatotilapia species from Lake Kabaleka and other East African cichlids suggest intermediate hypoxia tolerance. Nevertheless, our study suggests that some generalized lacustrine haplochromines may leak through swamp corridors even under relatively extreme conditions.     

Influence of recirculation over COD and N-NH4 removals from landfill leachate by horizontal flow constructed treatment wetland

Abstract

Treatment of landfill leachate is a challenge due to its complex chemical composition and high recalcitrance and because of high costs for conventional wastewater treatment. In our study, leachate from the Quitaúna Landfill, Sao Paulo Metropolitan Region, Brazil, was treated at a laboratory scale with a horizontal subsurface flow constructed treatment wetland (HF-CTW) operating under a recirculation regime. Two units planted with Heliconia psittacorum (HP) and Cyperus papyrus (CP), and one unplanted control unit were assessed. With a recirculation regime over 21?days, the planted units removed 40% of chemical oxygen demand (COD) while the control unit removed only 29%. True color removal efficiencies were 2, 22, and 23% for the control, HP, and CP HF-CTWs, respectively. The ammonium nitrogen removal efficiencies for a 21-day hydraulic retention time (HRT) were 63–81% for planted units and 72% for the control. The increase of the HRT from 7 to 21?days led to the enhancement of ammonium nitrogen removal but did not affect the COD and total nitrogen removals. This phenomenon is a consequence of leachate’s low biodegradability. The present study shows the importance of the HRT and plant presence for landfill leachate treatment using HF-CTWs.