An environmental engineering approach to wastewater treatment with bivalves in the coastal zone

High tolerance to pollution and filtration capacity of some seston-eating bivalves and mussels of g. Mytilus first of all, principally determine mussel populations as a powerful natural biofilter. Both marine and freshwater mussels consume relatively large amounts of seston, feeding directly on the primary producers. Particles with contaminants extracted from ambient water during the filtration are accumulated in mussel pseudofaeces and faeces discharged after digestion. These specific particles of faeces and soft pseudofeaces become very suitable substrata for bacteria development with following contaminant destruction. Moreover, such biodeposits appeared to be the nutritious food for bottom detritophages, in particular of polychaetes and amphipods. Some fluid metabolites excreted by mussels, i.e. dissolved organic matter (DOM) have a pronounced biological activity to producers. In general, mussels possess high resistance to acute and chronic pollution stress, although their growth may slow down and even stops. In clean conditions food supply is the most important factor in determining activity and growth rate of mussels for northern environment. Mussel and some other aquaculture, as a relatively new application of environmental engineering is able to improve the recycling of nutrients from wastewater to bioproduction and greatly reduce the risk of environmental degradation in the coastal zone.

Comparative Study on Physicochemical Parameters Study of Oil Polluted Sites and Hydrocarbon Degradation Potentials of Heterotrophic Bacteria in Southern Nigeria

In this study, hydrocarbon degradation potentials of heterotrophic bacteria isolated from oil-polluted soil were examined; Samples were collected from Sakpenwa, an oil producing community in Tai LGA of Rivers State. The amounts of hydrocarbon in the soil samples were determined using Gas Chromatography-Flame Ionization Detector, GC- FID. The gravimetric analysis showed that the bacteria were capable of utilizing 96.9-99.7% the oil sample. Analysis of variance (ANOVA) carried out at 95% level of confidence showed that the degree of hydrocarbon degradation varied amongst isolates. Pseudomonas aeruginosa and Alcaligenes sp. showed highest degrading activities while Bacillus subtilis showed least activity. This study revealed that indigenous bacterial species possess the requisite gene necessary for hydrocarbon biodegradation. Biodegradation is most often the primary mechanism for contaminant destruction in the environment including petroleum contaminants.

Heterogeneous ultrasonic destruction of aqueous organic contaminants

Sonolysis is emerging as an effective advanced technology for destruction of organic pollutants in wastewater. The focus of this study is to investigate the potential of enhancing the sonochemical destruction of aqueous organics. Increasing the contaminant destruction rate will reduce the reaction time, and possibly reduce the cost of treatment. For this purpose, the effect of H2O2 and/or silica in the presence of ultrasound is examined for destruction of 2-chlorophenol (2-CP). The effect of silica dosage (1, 5, 10, and 20 g/L), peroxide dosage (50, 75, and 100 mg/L), and pH (3,7,and 11) is examined. Low solution pH provided higher destruction of 2-CP. The presence of peroxide or silica enhanced the destruction of 2-CP. The optimum silica dosage was 5 g/L. 100 mg/L of peroxide and 5 g/L of silica present together enhanced 2-CP sonolytic destruction by a factor of approximately 2 as compared to 2-CP destruction with ultrasound only.

Photocatalytic Oxidation of Toluene in Water From an Algae Pond With High Dissolved Oxygen Content

Water in well-mixed ponds containing photosynthetic algae has been observed to have an extremely high Dissolved Oxygen (DO) content. Up to four times saturation levels of DO have been recorded. Since DO is known to have an important role in the photocatalytic oxidation of organic contaminants in water, it was hypothesized that a faster rate of contaminant destruction would be observed in water drawn from algae ponds supersaturated with DO. In order to verify this hypothesis, a bench scale, batch-type photoreactor was constructed. Some baseline tests were performed to investigate the influence of UV intensity, water pH, and DO content on the photocatalytic destruction of toluene in water. An array of ultraviolet blacklight lamps in a lamp box was used to simulate solar ultraviolet radiation. First-order reaction rate constants were calculated from the destruction data, using a kinetic model proposed earlier. The reaction was found to proceed forward equally fast at pH 4 and 10. A power law relation was derived for the reaction rate dependence on UV intensity. Presence of DO in the water was found to be required for the reaction to go forward. Water from an algae pond, supersaturated with dissolved oxygen was spiked with toluene and destruction tests were then conducted in the same reactor. These tests did not show the expected improvement in destruction rates.

Photocatalytic Oxidation of Toluene in Water From an Algae Pond With High Dissolved Oxygen Content

Water in well-mixed ponds containing photosynthetic algae has been observed to have an extremely high Dissolved Oxygen (DO) content. Up to four times saturation levels of DO have been recorded. Since DO is known to have an important role in the photocatalytic oxidation of organic contaminants in water, it was hypothesized that a faster rate of contaminant destruction would be observed in water drawn from algae ponds supersaturated with DO. In order to verify this hypothesis a bench scale, batch type photoreactor was constructed. Some baseline tests were performed to investigate the influence of UV intensity, water pH and DO content on the photocatalytic destruction of toluene in water. An array of ultraviolet “blacklight” lamps in a lamp box was used to simulate solar ultraviolet radiation. First-order reaction rate constants were calculated from the destruction data, using a kinetic model proposed earlier. The reaction was found to proceed forward equally fast at pH 4 and 10. A power law relation was derived for the reaction rate dependence on UV intensity. Presence of DO in the water was found to be required for the reaction to go forward. Water from an algae pond, supersaturated with dissolved oxygen was spiked with toluene and destruction tests were then conducted in the same reactor. These tests did not show the expected improvement in destruction rates.