Although the practice of composting animal wastes for use as biofertilizers has increased in recent years, little is known about the microorganisms responsible for the nitrogen transformations which occur in compost and during the composting process. Ammonia is the principle available nitrogenous compound in composting material, and the conversion of this compound to nitrite in the environment by chemolithotrophic ammonia-oxidizing bacteria is an essential step in nitrogen cycling. Therefore, the distribution of ammonia-oxidizing members of the β subdivision of the class Proteobacteriain a variety of composting materials was assessed by amplifying 16S ribosomal DNA (rDNA) and 16S rRNA by PCR and reverse transcriptase PCR (RT-PCR), respectively. The PCR and RT-PCR products were separated by denaturing gradient gel electrophoresis (DGGE) and were identified by hybridization with a hierarchical set of oligonucleotide probes designed to detect ammonia oxidizer-like sequence clusters in the genera Nitrosospira and Nitrosomonas. Ammonia oxidizer-like 16S rDNA was detected in almost all of the materials tested, including industrial and experimental composts, manure, and commercial biofertilizers. A comparison of the DGGE and hybridization results after specific PCR and RT-PCR suggested that not all of the different ammonia oxidizer groups detected in compost are equally active. amoA, the gene encoding the active-site-containing subunit of ammonia monooxygenase, was also targeted by PCR, and template concentrations were estimated by competitive PCR. Detection of ammonia-oxidizing bacteria in the composts tested suggested that such materials may not be biologically inert with respect to nitrification and that the fate of nitrogen during composting and compost storage may be affected by the presence of these organisms.
Pig farms in Leningradskij Oblast, Russia are usually large (/20,000 to 60,000 pigs per farm. As these farms discharge pig slurry into the adjacent rivers flowing into the Baltic Sea, there is a potential risk for pollution of both the rivers and the sea. This risk was assessed at the Vostochnii pig complex, which holds 60,000 pigs. The impact of slurry treatment on water quality in the groundwater (GW) and the river Igolinka, the recipient of the treated slurry, was investigated. The results indicated that untreated and treated slurry from pig farm wastewater treatment systems are potential point sources of environmental pollution. Generally, the GW was characterized by rather high contents of ammonium and chemical and biological demand for oxygen (COD, BOD). Similarly, the river exhibited high COD and BOD, contained considerable amounts of suspended substances and total P, and small quantities of NO 3 -N and NH 4 -N. Of the biological parameters investigated, the elevated population of fungi and pathogenic faecal bacteria Escherichia coli (100 Á10,000 CFU E. coli cells ml (1 ) determined in the river posed a potential health risk. Equally important was the marked total P load in the river, part of which could be transported to the Baltic Sea, where it could trigger eutrophication.
Combined biological and physico-chemical treatment of filtered pig manure wastewater has been investigated on the pilot installation operated under ambient temperatures (15-20 degrees C) and included: i) UASB-reactor for elimination of major part of COD from the filtrate; (ii) stripper of CO2 + fluidised bed crystallisator for phosphate (and partially ammonia) removal from the anaerobic effluents in the form of insoluble minerals-struvite (MgNH4PO4) and hydroxyapatite (Ca5(PO4)3OH); (iii) aerobic-anoxic biofilter for polishing the final effluent (elimination of remaining BOD and nutrients). Under overall hydraulic retention time (HRT) for the system of 7.8 days, the total COD, inorganic nitrogen and total phosphorous removals were 88, 65 and 74%, respectively. A decrease of the overall HRT to 4.25 days led to 91, 37 and 82% removals for total COD, inorganic nitrogen and total phosphorus removals, respectively. The approaches for further improvement of effluent quality are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.