Scientists at the Tennessee Valley Authority (TVA), and in collaboration with the U.S. Environmental Protection Agency (EPA), are continuing to develop and refine an innovative wastewater treatment system referred to as reciprocating subsurface-flow constructed wetlands. Reciprocation relates to patented improvements in the design and operation of paired subsurface-flow constructed wetlands, such that contiguous cells are filled and drained on a frequent and recurrent basis. This operating technique turns the entire wetland system into a fixed-film biological reactor, in which it is possible to control redox potential in alternating aerobic and anaerobic zones. Reciprocating systems enable manipulation of wastewater treatment functions by controlling such parameters as hydraulic retention time, frequency of reciprocation, reciprocation cycle time, depth of reciprocation, and size and composition of substrate. These improved wetland technologies have been used for treating municipal/domestic wastewater, high strength animal wastewater, and mixed wastewater streams containing acids, recalcitrant compounds, solvents, antifreeze compounds, heavy metals, explosives, and fertilizer nutrients. Results from selected treatability studies and field demonstrations will be summarized with respect to conceptual design and treatment efficacy.

Several different types of constructed wetland systems are being used as decentralized treatment systems including surface-flow, subsurface-flow, vertical-flow, and hybrid systems. Archetypical wetland systems have design strengths and weaknesses, and therefore it should be possible to design combined (integrated) systems to optimize a number of important treatment processes. This study provides comparative efficacy data for two integrated wetland treatment systems (IWTS) designed to enhance treatment of medium strength wastewater generated from a pilot-scale intensive fish farm. Results from the twenty eight months study included consistently high removal of COD (84% +) and ammonia nitrogen (93%) in both systems. Initially, phosphorus removal was also high (>90%) in both systems, but removal efficacy declined significantly over time. Nitrate removal was significantly better in the system that provided sequential aerobic and anoxic environments. Short hydraulic retention times coupled with sustained removal of COD and ammonia indicate that the ReCip components could be a least-cost wastewater treatment technology in the decentralized market sector.

Innovative wastewater treatment systems are needed for removing nutrients, noxious odors, dissolved organic matter, and pathogens from high strength agricultural and processing wastewater. A novel reciprocating subsurface-flow constructed wetland, consisting of four cells totaling 3570 m 2 (1.5 m deep), has been treating anaerobic lagoon wastewater from a commercial-scale confined swine feeding operation since November, 2000. The system, located near Aliceville, Alabama, has been monitored for twenty-one months. Hydraulic loading rates (HLR), from the anaerobic lagoon to the wetlands treatment system averaged 107 and 208 m 3 /day for years I and II respectively. Results to date indicate that the system's treatment efficacy is sustainable, with the exception of phosphorus removal. Doubling the flow temporarily reduced treatment efficacy with respect to monitored parameters. Average influent and effluent concentrations (ppm), of monitored parameters and their respective percentage removal rates were: CBOD 5 (521, 117, 78%); COD (1388, 393, 72%); NH 4-N (371, 51, 86%); and PO 4-P (52, 43, 17%). Electrical demand to operate reciprocating pumps, influent pumps and irrigation pumps averaged 203 kWh/day and 234.1 for the two wastewater loading rates respectively. Based on comments from farm workers and subjective laboratory testing, the system was effective in removing odors from lagoon effluent. Fecal coliform bacteria removal rates ranged from 2-3 Log reduction. In conclusion, the reciprocating wetland system was user friendly, relatively cost effective, and efficient with respect to removal of organic compounds, nitrogen, odor and fecal coliform bacteria. Further research will be required to enhance phosphorus removal.

Session No.: 71Scientists at the Tennessee Valley Authority (TVA), in collaboration with the U.S. Environmental Protection Agency (EPA), have developed an innovative wastewater treatment system based on reciprocating subsurface-flow constructed wetlands. Reciprocation relates to patented improvements in the design and operation of paired subsurface-flow constructed wetlands in which contiguous wetland cells are filled and drained on a recurrent basis. This operating technique turns the entire wetland system into a fixed-film biological reactor, in which it is possible to have alternating aerobic and anaerobic zones. The treatment systems biological structure and function are controlled by such parameters as hydraulic retention time, frequency of reciprocation, reciprocation cycle time, depth of reciprocation, and size and composition of substrate. Reciprocation facilitates enhanced removal of biochemical oxygen demand (BOD), metals, and nutrients such as nitrogen and phosphorus.A preliminary treatability study was conducted in replicate 75 liter microcosms to simultaneously evaluate the influence of BOD loading rates (50-400 mg/L), reciprocation cycle times (0, 1 and 2) and the presence or absence of plants (Reed Canary grass, Phalaris arundinacea). Phosphorus and ammonia nitrogen were added to all treatments at 50 and 100 mg/L). Irrespective of BOD loading rates, treatments without reciprocation had oxidation-reduction potentials (ORP), drop to less than -300 to -500 mV within 24 hours and these values were maintained for the duration of the eight day study. Results indicated significant improvements in treatment efficacy due to the dual action of reciprocation and plants. In reciprocating treatments with plants, simultaneous nitrification and denitrification processes resulted in total nitrogen removal ranging from 95 to 99%. Reciprocation with plants also improved removal of BOD and ortho-and total-phosphorus.

O e g r i l n d e t 1 9 2 8 u n t e r d e m T l t e l , , D i e c h e m i s c h e F a b r l k " 40. Jahrgang -17. Mai 1968 -Heft 9/10 -Seite 41 3-508 CHEMIE INGENIEUR ITECHNIK I In der europaischen Entwicklung von Leistungsreaktoren zeichnet sich eine neue Stufe ab, die zur Projektion eines natrium-und eines dampfgekiihlten Schnellbruter-Prototyps geiuhrt hat. Schnellbriiter-Kernkraftwerke sollen in Deutschland etwa ab 1980 wirtschaftlich arbeiten. Nach einem Uberblick uber verschiedene Reaktortypen und -strategien und uber den jeweiligen Uran-Bedarf werden wirtschaitliche Vorteile von Schnellbriiter-Kernkraftwerken genannt (wie geringe Energieerzeugungskosten, Unabhangigkeit von Uran-Reserven und Konvertern sowie Vielseitigkeit im Aufbau), die eine Anpassung an die technischen und wirtschaftlichen Verhaltnisse erlauben. 414 Chemie-1ng.-Techn. 40. Jahrg. 1968 /Heft 9/10 16) D. Gupta: Der geschlossene Brennstoffzyklus Schneller Brntreaktoren und dessen Kostenanalyse (in Vorb.). 17) P. Jansen: BAKO, Ein Programm zur Kosten-und Strategieberechnung von Bruterkraftwerken rnit der Barwertmethode, KFK-Bericht 644 (1967).

Am Beispiel des Rheins wird untersucht, wie die mit Frischwasserkuhlung installierbare Kraftwerksleistung von verschiedenenparametern abhangt. DieseParameter sind : die maximal zulassige Erwarmung gegenuber dem natiirlichen Zustand, die zulassige Hochsttemperatur, die geforderte Auslastbarkeit der Kraftwerke, der Kraftwerkswirkungsgrad sowie die meteorologischen und hydrologischen Daten, die fur die naturliche Abkuhlung des Flusses von Bedeutung sind. Es zeigt sich, dalj das Abwarmeproblem mit Frischwasserkuhlung nur fur einen sehr begrenzten Zeitraum 10sbar ist, wenn man nicht die Okologie des Flusses vollig veriindern will. Insbesondere wird dargestellt, welche starken Veranderungen sich schon bei relativ geringen Erwarmungen aufgrund des Synergismus zwischen Erwarmung und organischer Verschmutzung ergeben. Als SchluBfolgerung wird auf die Notwendigkeit okologischer und technologischer Analysen beim Ubergang auf andere Kiihlmoglichkeiten hingewiesen. Der Warmelastplan Rhein der Arbeitsgemeinschaft der Lander zur Reinhaltung des Rheins [l] weist aus, dalj am Rhein die folgenden Kraftwerksleistungen installiert waren bzw. sein werden: 1970 1975 1985 6,1 GWe, 17,l GWe, 43,l GWe.

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