ABSTRACT
Consequences of orthophosphate addition for corrosion control in water distribution pipes with respect to microbial growth were investigated using batch and dynamic tests. Batch tests showed that the release of copper in either low or high organic carbon content water was decreased by 69% and 56% with addition 206 microg PO(4)-P, respectively. Dosing of orthophosphate against corrosion did not increase microbial growth potential in the water and in the biofilm in both corroded and uncorroded systems receiving tap water with a low content of organic carbon and of biodegradable organic fraction. However, in tap water having a high concentration of organic carbon from acetate addition, orthophosphate addition promoted the growth of bacteria, allowed more bacteria to assemble on corroded and uncorroded surfaces, and increased the consumption of organic carbon. Orthophosphate consumption did not exceed 1% of the amount of easily biodegradable organic carbon required for microbial growth, and the orthophosphate demand for corrosion control greatly exceeded the nutritional requirement of microbial growth. The results of the dynamic tests demonstrated that there was a significant effect of interaction between biodegradable organic carbon and orthophosphate on biofilm growth, whereby the effect of orthophosphate flux on microbial growth was dependent on the levels of biodegradable organic carbon. Controlling an easily biodegradable organic carbon would be therefore necessary to minimize the microbial growth potential induced by orthophosphate-based anticorrosion treatment.
Subject(s)
Carbon/pharmacology , Copper/metabolism , Organic Chemicals/pharmacology , Phosphates/pharmacology , Plastics/chemistry , Sanitary Engineering , Water Microbiology , Bacteria/drug effects , Bacteria/growth & development , Biofilms/drug effects , Carbon/chemistry , Copper/chemistry , Corrosion , Organic Chemicals/chemistry , Water/chemistryABSTRACT
Three different bioassays for analysis of biodegradable dissolved organic carbon (BDOC) were evaluated to identify which method is most applicable to analysis of drinking water. The determination of BDOC is primarily based on the differences between initial and final DOC levels during a certain incubation period using indigenous bacterial consortium as an inoculum. The assay procedures basically differ in the preparation method of inoculum. Inoculum was added in the form of suspended bacteria in one assay. In the other two assays, bacterial inoculum attached to either sand or inert media was used in a continuous reactor column. Standard solutions containing sodium acetate, sodium oxalate, or glucose at 1 mg C/L, and tap water were tested. The bioassay using bacteria attached to sand was shown to be superior to the two other methods for BDOC determination in terms of its incubation period, recovery, and reproducibility. Tap water samples, when analyzed by this assay, could not be guaranteed for biological stability due to their high BDOC concentrations (0.17 to 0.23 mg/L) that corresponded to 26-36% of the initial DOC level.
Subject(s)
Carbon/analysis , Water Supply , Bacteria/growth & development , Biodegradation, Environmental , Biological Assay/methods , Sensitivity and Specificity , Silicon Dioxide , SolubilityABSTRACT
This article presents the experimental work for the treatment of landfill leachate in a combined process using the white rot fungus Phanerochaete chrysosporium and the natural zeolite Clinoptilolite. Clinoptilolite was used in a pretreatment step as a sink for ammonia nitrogen and, on average it reduced the levels of ammonia nitrogen, soluble chemical oxygen demand (COD) and color by 72, 4.7, and 25%, respectively. The reductions by fungal treatment alone were 16.6, 21.5, and 31.2%, respectively. However, a reduction in nitrogen loading greatly enhanced fungal treatment efficiency. A high C/N ratio in the leachate was found preferable for the fungal treatment. With the synergy created by pretreatment and fungal growth that was stimulated by the addition of a growth medium, the process could remove ammonia nitrogen, soluble COD (SCOD) and color at levels as high as 81.5, 65, and 59%, respectively. The ratio of SBOD5/SCOD increased from 0.1 to 0.17 upon treatment, indicating that the process rendered the leachate more amenable to the biological process. This result suggested that the preliminary reduction of ammonia nitrogen was essential in making the fungal process practicable for landfill leachate treatment.
