Effect of different sewage sludge applications on growth and yield of Vigna radiata L. field crop: Metal uptake by plant

The aim of this study was to assess the suitability of sewage sludge use for mung bean {Vigna radiata L. cv. Malviya janpriya (HUM 6)} plants by evaluating the growth, and yield responses, nutritional quality and heavy metal accumulation at different sewage sludge amendment (SSA) rates. Sewage sludge amendment modified the physico-chemical properties of soil by decreasing pH and increasing organic carbon, total iron and heavy metals. Plants showed increments in shoot length, leaf area and total biomass at all SSA rates, but root length increased only up to 9 kg m^?2 SSA rates. Plants grown at different SSA rates showed higher nutrients and heavy metals in seeds, but protein content declined. Sewage sludge application caused about 39, 76 and 60% more yield at 6, 9 and 12 kg m^?2 treatments, respectively. Concentrations of Pb and Ni in grains were higher than the Indian permissible limits at and above 9 kg m^?2 and of Cd at 12 kg m^?2 SSA rates.The study suggests that SSA at a rate lower than 9 kg m^?2 may be recommended due to better fertilizing value for soil and promoting mung bean yield. Higher rate of sewage sludge application leads to elevated accumulation of heavy metals in seeds, which limits the suitability for human consumption.     

Nitrate removal and hydraulic performance of organic carbon for use in denitrification beds

Denitrification beds are a cost-effective technology for removing nitrate from point source discharge. To date, field trials and operational beds have primarily used wood media as the carbon source; however, the use of alternative more labile carbon media could provide for increased removal rate, lower installation costs and reduced bed size. While previous laboratory experiments have investigated the potential of alternative carbon sources, these studies were typically of short duration and small scale and did not necessarily provide reliable information for denitrification bed design purposes. To address this issue, we compared nitrate removal, hydraulic and nutrient leaching characteristics of nine different carbon substrates in 0.2 m³ barrels, at 14 and 23.5 °C over a 23-month period. Mean nitrate removal rates for the period 10–23 months were 19.8 and 15 g N m^?3 d^?1 (maize cobs), 7.8 and 10.5 g N m^?3 d^?1 (green waste), 5.8 and 7.8 g N m^?3 d^?1 (wheat straw), 3.0 and 4.9 g N m^?3 d^?1 (softwood), and 3.3 and 4.4 g N m^?3 d^?1 (hardwood) for the 14 and 23.5 °C treatments, respectively. Maize cobs provided a 3–6.5-fold increase in nitrate removal over wood media, without prohibitive decrease in hydraulic conductivity, but had higher rates of nutrient leaching at start-up. Significant difference in removal rate occurred between the 14 and 23.5 °C treatments, with the mean Q₁₀ temperature coefficient = 1.6 for all media types in the period 10–23 months.     

Biotrickling air filtration of 2-chlorophenol at high loading rates

The degradation of 2-chlorophenol vapours in air was performed in a trickling biofilter packed with ceramic material seeded with the bacterium Pseudomonas pickettii, strain LD1. The system performance was evaluated under varying operating conditions (inlet 2-chlorophenol air concentrations from 0.10 to 3.50 g m^?3, and superficial air velocities of 30.0, 60.0, and 120.0 m h^?1). For all air velocity the maximum degradation rate was obtained for loading rates of 40 g m^?2 h^?1. Higher loading conditions resulted in strong inhibition of microbial activity, particularly severe at high air velocity. Process analysis, performed using data on pollutant concentration profiles along the filter packing obtained under different conditions of inlet concentration and air velocity, proves that best performance (i.e. maximum degradation efficiency and capacity) can be obtained for a narrow range of operating conditions, which can be ensured by proper design of biofilter size (i.e. diameter and height). Kinetic analysis of experimental data confirms that 2-CP inhibits microbial activity in the biofilter bed. Experimental data are satisfactorily fitted by the Haldane kinetic equation up to a critical value of loading rate, beyond which the experimental degradation rate is overestimated by the kinetic model. The inhibition appears to be affected by the loading rate, and the estimated inhibition constant linearly increases with increasing empty bed residence time.     

Influence of urea and calcium dosage on the effectiveness of bacterially induced carbonate precipitation on limestone

Bacterially induced carbonate precipitation has been explored for the protection and consolidation of ornamental stone. Attempts to improve the efficiency of this biodeposition process were primarily focused on the microbial aspects, i.e. type of microorganism and metabolic pathway. In this study, the influence of the chemical parameters, i.e. concentration of calcium salts and urea, on the effectiveness of the biodeposition treatment has been examined. The amount of calcium carbonate that can be precipitated in the stone is conditioned both by the amount of cells retained in the stone and the concentration of urea and calcium used. From sonication experiments, a good consolidation was observed for limestone prisms treated with a calcium dosage of 17 g Ca²⁺ m^?2 with no improvement at higher concentrations. For limestone prisms of 4 cm × 2 cm × 1 cm, the biodeposition treatment resulted in a 63% lower weight loss upon sonication compared to untreated specimens. The waterproofing effect was observed to increase with increasing calcium dosages. While for a calcium dosage of 17 g Ca²⁺ m^?2 the water absorption was similar to that of untreated specimens, concentrations of 67 g Ca²⁺ m^?2 resulted in a 50% decrease of the rate of water absorption. For calcium dosages higher than 34 g Ca²⁺ m^?2 a significant change in the visual aspect (ΔE > 6) of the treated stones could be observed. Overall, the urea/calcium chloride-based biodeposition treatment attained a protective performance comparable with that of the commonly used ethylsilicates.     

Nitrate removal rates in woodchip media of varying age

A variety of low-cost carbonaceous solids have been successfully tested in bioreactors designed for nitrate treatment. In many agricultural and wastewater settings, however, such reactors may be practical only if they are maintenance free for a number of years after installation. Although field installations have demonstrated consistent treatment over multi-year timeframes, the ability to accurately quantify slowly declining reaction rates in field settings is problematic because of variations in reactor flow rates, ambient temperatures and influent chemistry. In this study, laboratory column tests were undertaken on four samples of coarse wood particle media (woodchips), two that were fresh and two that had been in continuous operation in subsurface denitrifying bioreactors for periods of 2 and 7 years respectively. Four experimental runs were undertaken at increasing influent NO₃-N concentrations of from 3.1 to 48.8 mg N L^?1. Nitrate mass removal rates remained relatively constant and did not systematically increase in successive runs at higher NO₃ concentrations indicating that NO₃ was not the rate-limiting substrate at these concentrations. Thus, zero-order reaction kinetics were used to model the attenuation reaction (presumably denitrification). The 7-year-old media had a mean NO₃-N removal rate of 9.1 mg N L^?1 d^?1 (6.4 g N m^?3 media d^?1), which remained within 75% of the rate for the 2-year-old media (12.1 mg N L^?1 d^?1 or 8.5 g N m^?3 media d^?11) and within 40–59% of the rate for the fresh chips (15.4–23.0 mg N L^?1 d^?1 or 10.8–16.1 g N m^?3 media d^?1). Results support field experience indicating that woodchips loose about 50% of their reactivity during their first year of operation as soluble organic compounds are leached out, but then relatively stable rates persist for a considerable number of years thereafter.     

Phosphorus removal from agricultural runoff by constructed wetland

A free-water surface wetland covering an area of 2800 m² was operated from March 2002 to June 2004 for agricultural runoff treatment in the Dianchi Valley in China. In the wetland were grown Zizania Caduciflora Turez Hand-mazt and Phragmites australis (Cav.) Trin.ex Steud. The instantaneous inflow rate was measured and the integrated flux was recorded by an ultrasonic flow instrument all year round. The average inflow rate, hydraulic loading rate (HLR) and hydraulic retention time (HRT) were kept at 242 m³ d^?1, 12.7 cm d^?1 and 2.0 d, respectively. The annual average total phosphorus (TP) in the inflow was 0.87 mg L^?1, and the corresponding removal efficiency was calculated to be 59.0%. Biannual plant uptake and removal by harvesting and seed transport was the main pathway for TP removal, while the influent TP load was 12.9 g m^?2 year^?1. Hydraulic retention time had a significant positive correlation with the removal of P (r² = 0.88). Water temperature, inflow phosphorus load, inflow and hydraulic load rates were positively correlated with the removal of P. Inflow phosphorus concentrations were negatively correlated with the removal of P. It is shown that the free-water surface wetland was an effective and economical system for agricultural runoff treatment in lake regions.     

Effects of rest grazing on organic carbon storage in Stipa Baicalensis steppe in Inner Mongolia

In order to evaluate the potential effects of rest grazing on organic carbon storage on the Stipa baicalensis steppe in Inner Mongolia, compared the S. baicalensis steppes after rest grazing for 3 years, 6 years, and 9 years, using potassium dichromate heating method, this study analyzed the organic carbon storage of plant and soil in the steppes among different periods of rest grazing. The results indicated that as the rest grazing years prolonged, the biomass included above-ground parts, litters and underground plant parts(roots) of the plant communities all increased, meanwhile the carbon content of the biomass increased with the rest grazing years prolonged. For the zero rest grazing (RG0) steppe and the steppes after a rest grazing of 3 years (RG3a), 6 years (RG6a), 9 years (RG9a), the carbon storage in above-ground parts of plant communities were 42.60 g C/m², 66.33 g C/m², 83.46 g C/m², 100.29 g C/m² respectively; the carbon storage of litters were 7.85 g C/m², 9.12 g C/m², 9.18 g C/m², 11.54 g C/m² separately; the carbon storage of underground plant parts (0–100 cm) were 281.40 g C/m², 576.38 g C/m², 745.33 g C/m², 1279.61 g C/m² respectively; and the carbon storage in 0–100 cm soil were 22991.14 g C/m², 24687.75 g C/m², 26564.86 g C/m²,33041.55 g C/m². The results suggested that as the rest grazing years prolonged, the organic carbon storage in plant communities and soil increased. The carbon storage of underground plant parts and soil organic carbon mainly concentrated in 0–40 cm soil. After rest grazing for 3 years, 6 years, and 9 years, the increased soil organic carbon were as the 81.14%, 85.84%, and 89.46% of the total increased carbon; From the perspective of carbon sequestration cost, the total cost of RG3a, RG6a and RG9a were 2903.40 RMB/hm², 5806.80 RMB/hm², and 8710.20 RMB/hm². The cost reduced with the extension of rest grazing years, 0.17 RMB/kg C, 0.16 RMB/kg C, 0.09 RMB/kg C for RG3a, RG6a and RG9a respectively. From the growth characteristics of grassland plants, the spring was one of the two avoid grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. From the available data, the organic carbon storage of RG9a was the highest, while the cost of carbon sequestration was the lowest. Therefore, spring rest grazing should be encouraged to continue for it was proved to be a very efficient grassland use measures.     

Denitrification of nitrified and non-nitrified swine lagoon wastewater in the suspended sludge layer of treatment wetlands

One method for managing livestock-wastewater N is the use of treatment wetlands. The objectives of this study were to (1) assess the magnitude of denitrification enzyme activity (DEA) in the suspended sludge layers of bulrush and cattail treatment wetlands, and (2) evaluate the impact of nitrogen pretreatment on DEA in the suspended sludge layer. The study used four wetland cells (3.6 m × 33.5 m) with two cells connected in series. Each wetland series received either untreated or partially nitrified swine wastewater from a single-cell anaerobic lagoon. The DEA of the suspended sludge layers of the constructed wetlands was measured by the acetylene inhibition method. The control DEA treatment for the sludge layer had a mean rate of 18 μg N₂O-N g^?1 sludge h^?1. Moreover, the potential DEA (nitrate-N and glucose-C added) mean was very large, 121 μg N₂O-N g^?1 sludge h^?1. These DEA rates are consistent with the previously reported high levels of nitrogen removal by denitrification from these wetlands, especially when the wastewater was partially nitrified. Stepwise regression using distance within the wetland, wastewater nitrate, and wastewater ammonia explained much of the variation in DEA rates. In both bulrush and cattail wetlands, there were zones of very high potential DEA.     

Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus

The ability of vertical flow (VF) constructed wetland systems to treat high-strength (ca. 300 mg L^?1 of COD and ca. 300 mg L^?1 total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6 m) were used: three units were planted with Typha angustifolia L., another three units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80 mm d^?1. Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water. The high evapotranspirative water loss from the Cyperus systems resulted in higher effluent concentrations of COD and total-P, but the mass removal of COD did not differ significantly between planted and unplanted systems. Average mass removal rates of COD, TKN and total-P at a HLR of 80 mm d^?1 were 17.8, 15.4 and 0.69 g m^?2 d^?1. The first-order removal rate constants at a HLR of 80 mm d^?1 for COD, TKN and total-P were 49.8, 30.1 and 13.5 m year^?1, respectively, which is in the higher range of k-values reported in the literature. The oxygen transfer rates were ca. 80 g m^?2 d^?1 in the planted systems as opposed to ca. 60 g m^?2 d^?1 in the unplanted systems. The number of Nitrosomonas was two to three orders of magnitude higher in the planted systems compared to the unplanted systems. Planted systems thus had significantly higher removal rates of nitrogen and phosphorus, higher oxygen transfer rates, and higher quantities of ammonia-oxidizing bacteria. None of the systems did, however, fully nitrify the wastewater, even at low loading rates. The vertical filters did not provide sufficient contact time between the wastewater and the biofilm on the gravel medium of the filters probably because of the shallow bed depth (0.6 m) and the coarse texture of the gravel. It is concluded that vertical flow constructed wetland systems have a high capacity to treat high-strength wastewater in tropical climates. The gravel and sand matrix of the vertical filter must, however, be designed in a way so that the pulse-loaded wastewater can pass through the filter medium at a speed that will allow the water to drain before the next dose arrives whilst at the same time holding the water back long enough to allow sufficient contact with the biofilm on the filter medium.     

Methanol vapor biofiltration coupled with continuous production of recombinant endochitinase Ech42 by Pichia Pastoris

Methanol biofiltration using methylotrophic microorganisms has been previously reported by various authors. In a previous study, a modified strain of Pichia pastoris was tested for the ability to produce endochitinase (Ech42) when coupled with methanol vapor biodegradation in batch tests. The next challenge was to validate the process in a continuous system. Thus, in the present study, a biofilter packed with perlite and inoculated with P. pastoris transformed with the plasmid pPIC-ech42 was used for methanol vapor biofiltration and the continuous production of recombinant endochitinase (Ech42) for 60 days. The maximum elimination capacity (EC) of methanol obtained was 1320 g m^?3 h^?1 at a loading rate of 1465 g m^?3 h^?1. The extracellular protein production rate in the leachate was 2360 μg h^?1 with a chitinase enzymatic activity of 123 U L^?1. The protein content on the biofilm samples was negligible, indicating the effectiveness of the overall process and of P. pastoris to excrete proteins. The carbon balance indicated that 81% of the consumed methanol was mineralized and 5.8% was incorporated into biomass. The results of this study and the economic balance underscore the promising application of linking methanol vapor biofiltration to the continuous production of recombinant proteins.     

Solids hydrolysis and accumulation in a hybrid anaerobic digester-constructed wetlands system

The properties and behaviour of solids retained in a pilot plant constituted of an up-flow anaerobic sludge blanket (UASB) reactor and two constructed wetlands (CWs) were monitored over a 3-year period. The UASB (25.5 m³) was fed with raw municipal wastewater at a flow rate of 61–112 m³ d^?1 and a volumetric loading rate (VLR) of 0.75–1.70 kg TCOD m^?3 d^?1. The CWs (75 m² each) were operated in series and received a fraction (17–20 m³ d^?1) of the UASB effluent. The applied surface loading rates (SLR) were in the range of 3800–8700 g TCOD m^?2 d^?1 (UASB) and 11–15 g BOD₅ m^?2 d^?1 (CWs). The overall system removed 95% TSS, 85% TCOD and 87% BOD₅ on average. For influent VSS, the UASB removed 72.1% and gave a hydrolysis of 63.5%, while the average surplus sludge generation was 8.7%. Over the 3-year period, TSS and VSS accumulated in the CWs at rates of 1.07 and 0.56 kg m^?2 year^?1, respectively. The aerobic biodegradability of the accumulated solids ranged from 23 to 92 mg O₂ g VSS^?1 d^?1 and increased downstream in the CWs. About 59% of the VSS that entered the CWs was removed by hydrolysis, while 24% accumulated on granular media. These low solids accumulation rates were especially remarkable considering the high COD and BOD₅ loading rates applied. The system lay-out appear to be promising in terms of preventing clogging.     

Performance of West African dwarf goats fed Guinea grass–Verano stylo mixture,N-fertilized and unfertilized Guinea grass

The supplementary values of Verano stylo in a mixed Guinea grass (Panicum maximum cv. Ntchisi)–Verano stylo (Stylosanthes hamata cv. Verano) diet from a sown grass–legume mixture and N fertilized grass were compared in West African dwarf (WAD) goats. Liveweight (LW) gain, feed intake, digestibility and N utilization were determined using 15 goats in two trials lasting for 98 days. Goats were fed Guinea grass–Verano stylo mixture (GSM), N-fertilized (NFG) and unfertilized grass (UFG). The goats were divided into three groups of five animals each and randomly allocated to the dietary treatments in a randomized complete block design. Total DM and OM intakes of the goats did not vary significantly among the forage diets and averaged 55.1 and 50.4 g kg⁻¹ W^0.75 per day, respectively. CP intake (g kg⁻¹ W^0.75 per day) was highest with NFG (5.6) followed by GSM (4.8) and the UFG (3.5). Total N excreted followed the same trend as the CP intake. There was no significant difference between N-retention of GSM and NFG (28.5 and 26.7%), but goats on UFG had a negative N balance (−9.16%). Animals on GSM had significantly higher liveweight gain (31.9 g per day) than those of NFG (25.1 g per day) and UFG (21.9 g per day) which also differed significantly. The digestibilities of total DM, OM, CP, NDF were higher with GSM than NFG or UFG. It is concluded that growing Verano stylo in mixture with Guinea grass is a better option for improving the feed quality of forage diets for goats than direct application of inorganic fertilizer at 200 kg N ha⁻¹ to the pure grass.     

Tradescantia fluminensis,an exotic weed affecting native forest regeneration in New Zealand: Ecological surveys,safety tests and releases of four biocontrol agents from Brazil

In the native range of Tradescantia fluminensis in SE Brazil surveys revealed a natural enemy biota attacking the plant that was rich in potential biocontrol agents for New Zealand (NZ), including nine fungi and 10 herbivorous insect species. Similar surveys in NZ, where T. fluminensis is an invasive exotic weed, revealed no specialist insect herbivores or pathogens. The Brazilian insect herbivores included leafmining, stemboring and gall-forming feeding guilds that were absent in NZ. Mean foliar damage levels per site on T. fluminensis were 7.8× higher for folivores in Brazil cf. NZ, and 21.2× higher for pathogens. The presence of rust pustules, or ‘brown lesions’, on leaves in Brazil was negatively associated with damage by folivores, perhaps indicating an antagonistic interaction. In contrast, damage by the white smut fungus, Kordyana sp., was not negatively associated with folivore damage. Mean dry biomass of T. fluminensis was significantly lower in Brazil (164 g m^?2) cf. NZ (455 g m^?2). In NZ, 85% of sites had biomass measures >200 g m^?2 (the previously determined threshold above which native forest regeneration fails). In Brazil, only 27% of sites had biomass measures >200 g m^?2. Among the insect herbivores, three chrysomelid beetles, Neolema ogloblini, Neolema abbreviata and Lema basicostata were prioritised as potential biocontrol agents. Their larvae cause potentially complementary damage to leaves, shoot-tips and mature stems, respectively. Several pathogens, including a rust, were rejected before we selected the Kordyana species. Host range testing of all four agents showed sufficient host-specificity for consideration for release in NZ. Neolema ogloblini and L. basicostata were field-released in NZ in 2011 and 2012, with the field-release of N. abbreviata due late 2012. An application to release Kordyana sp. in NZ has been made.     

NH3 gas absorption and bio-oxidation in a single bioscrubber system

A combined ammonia gas absorption and nitrification was conducted in a single bioscrubber. The reactor was consisted of a bubble column (gas absorption) and a packed bed (nitrification) which contained poly-urethane foams with immobilized nitrifying activated sludge. The entering gas and scrubbing liquid were contacted countercurrently. The bubble column elimination capacity (EC) was 26.74 g NH₃/m³ h at >99% ammonia gas removal and effluent gas concentration lower than 2 ppm_v. Without ammonium supplement, EC can reach 35.66 g NH₃/m³ h which is equivalently the highest tolerable ammonia loading rate of 700 g N/m³ day (1650 mg N/L) at the packed bed. At this level, 593 g N/m³-day ammonia removal rate was achieved via nitrification, dominated by ammonia oxidation. Partial recycling (R/Q = 0.5) of scrubbing solution reduced the secondary wastewater volume by producing 233% more concentrated nitrified products. Hydraulic retention time (HRT) of 24 h was found optimal for both processes (gas absorption and nitrification).     

Oxygen enhances the recovery of Potamogeton maackianus from prolonged exposure to very low irradiance

Recovery ability in relation to carbohydrate content of Potamogeton maackianus growing in two dissolved oxygen concentrations (8 and 2 mg L⁻¹) was investigated during 28 days exposure to very low irradiance (about 0.06 μmol m⁻² s⁻¹). Plant weight remained relatively constant (0.19 g dry wt plant⁻¹) within the initial 21 days in the high oxygen treatment, but decreased to 0.14 g dry wt plant⁻¹ at the end of the experiment. In low oxygen environments, plant weight was similar within the initial 14 days, but decreased to 0.08 g dry wt plant⁻¹ at 21 day. During the experimental period, both soluble sugar and starch contents in shoots decreased with time. Compared to high oxygen treatment, plants in the low oxygen treatment depleted starch more quickly (25 versus 18 mg g⁻¹ at 28 day) but remained a relatively high soluble sugar content (0.9 versus 1.8 mg g⁻¹ at 28 day). After recovery in high light and high dissolved oxygen conditions for 1 week, plant growth rate, new branch number, stem elongation rate and leaf recruitment number were significantly higher in high oxygen than in the low oxygen treatments. These data suggest that the ability of the plant to recover from prolonged exposure to very low irradiance is related to the depletion level of carbohydrate stored in plant tissues, which is regulated by oxygen availability in the water.     

Nitrate removal and greenhouse gas production in a stream-bed denitrifying bioreactor

Denitrifying bioreactors are currently being tested as an option for treating nitrate (NO₃^?) contamination in groundwater and surface waters. However, a possible side effect of this technology is the production of greenhouse gases (GHG) including nitrous oxide (N₂O) and methane (CH₄). This study examines NO₃^? removal and GHG production in a stream-bed denitrifying bioreactor currently operating in Southern Ontario, Canada. The reactor contains organic carbon material (pine woodchips) intended to promote denitrification. Over a 1 year period, monthly averaged removal of influent (stream water) NO₃^? ranged from 18 to 100% (0.3–2.5 mg N L^?1). Concomitantly, reactor dissolved N₂O and CH₄ production, averaged 6.4 μg N L^?1 (2.4 mg N m^?2 d^?1), and 974 μg C L^?1 (297 mg C m^?2 d^?1) respectively, where production is calculated as the difference between inflow and effluent concentrations. Gas bubbles entrapped in sediments overlying the reactor had a composition ranging from 19 to 64% CH₄, 1 to 6% CO₂, and 0.5 to 2 ppmv N₂O; however, gas bubble emission rates were not quantified in this study. Dissolved N₂O production rates from the bioreactor were similar to emission rates reported for some agricultural croplands (e.g. 0.1–15 mg N m^?2 d^?1) and remained less than the highest rates observed in some N-polluted streams and rivers (e.g. 110 mg N m^?2 d^?1, Grand R., ON). Dissolved N₂O production represented only a small fraction (0.6%) of the observed NO₃^? removal over the monitoring period. Dissolved CH₄ production during summer months (up to 1236 mg C m^?2 d^?1), was higher than reported for some rivers and reservoirs (e.g. 6–66 mg C m^?2 d^?1) but remained lower than rates reported for some wastewater treatment facilities (e.g. sewage treatment plants and constructed wetlands, 19,500–38,000 mg C m^?2 d^?1).     

Toward scrubbing the bay: Nutrient removal using small algal turf scrubbers on Chesapeake Bay tributaries

Restoration of the Chesapeake Bay poses significant challenges because of increasing population pressure, conversion of farmland to urban/suburban development, and the expense of infrastructure needed to achieve significant and sustained nutrient reductions from agricultural and urban sources. One radical approach for removing non-point source nutrients before they reach the bay is to deploy large-scale algal turf scrubbers along its tributaries. The objective of this study was to determine rates of nutrient removal and algal fatty acid production using small ATS units located along three Chesapeake Bay rivers. Small-scale ATS units (each containing 1 m² growing area) were operated for 5–10 months from April 2007 to April 2008 on three western shore tributaries of the Chesapeake Bay in Maryland: the Bush River, the Patapsco River and the Patuxent River. Total nitrogen (TN) and total phosphorus (TP) removal rates at the Patuxent site fluctuated considerably but averaged 250 mg TN, 45 mg TP m^?2 day^?1 from May to October 2007, then decreased to 16 mg TN, 3 mg TP m^?2 day^?1 from December 2007 to February 2008. Nutrient removal rates at the Bush river site also fluctuated but averaged only 85 mg TN, 10 mg TP m^?2 day^?1 from May to June 2007, before decreasing to <10 mg TN, <1 mg TP m^?2 day^?1 from July to September 2007. The Patapsco River unit began operation in August 2007, reached its maximum removal values of 150 mg TN, 18 mg TP m^?2 day^?1 from mid-October to late-November 2007, then decreased to values of 45 mg TN, 4 mg TP m^?2 day^?1 from November 15, 2007 to mid-April 2008. In the best case (Patuxent site from May to October 2007), daily removal rates of 250 mg N and 45 mg P m^?2 are equivalent to removal rates of 380 kg N and 70 kg P ha^?1 over a 150-day season in Maryland. Fatty acid (FA) content of the harvested material was consistently low (0.3–0.6% of dry weight) and varied little between sites. Mean algal FA production rates (23–54 mg FA m^?2 day^?1) are equivalent to rates of 34–81 kg FA ha^?1 year^?1 based on a 150-day operational season in Maryland.     

Functional consortium for hydrogen production from cellobiose: Concentration-to-extinction approach

A functional bacterial consortium that can effectively hydrolyze cellobiose and produce bio-hydrogen was isolated by a concentration-to-extinction approach. The sludge from a cattle feedlot manure composting plant was incubated with 2.5–20 g l^?1 cellobiose at 35 °C and pH 6.0. The microbial diversity of serially concentrated suspensions significantly decreased following increasing cellobiose concentration, finally leaving only two viable strains, Clostridium butyricum strain W4 and Enterococcus saccharolyticus strain. This consortium has a maximum specific hydrogen production rate of 2.19 mol H₂ mol hexose^?1 at 5 g l^?1 cellobiose. The metabolic pathways shifted from ethanol-type to acetate-butyrate type as cellobiose concentration increased from 2.5 to >7 g l^?1. The concentration-to-extinction approach is effective for isolating functional consortium from natural microflora. In this case the functional strains of interest are more tolerant to the increased loadings of substrates than the non-functional strains.     

Nitrification rates of algal–bacterial biofilms in wastewater stabilization ponds under light and dark conditions

The objective of this study was to investigate nitrification rates in algal–bacterial biofilms of waste stabilization ponds (WSP) under different conditions of light, oxygen and pH. Biofilms were grown on wooden plates of 6.0 cm by 8.0 cm by 0.4 cm in a PVC tray continuously fed with synthetic wastewater with initial NH₄-N and Chemical Oxygen Demand (COD) concentrations of 40 mg l^?1 and 100 mg l^?1, respectively, under light intensity of 85–95 μE m^?2 s^?1. Batch activity tests were carried out by exposure of the plates to light conditions as above (to simulate day time), dim light of 1.8–2.2 μE m^?2 s^?1 (to simulate reduced light as in deeper locations in WSP) and dark conditions (to simulate night time). Dissolved oxygen (DO) concentration and pH were controlled. At some experiments, both parameters were kept constant, and at others they were left to vary as in WSP. Results show biofilm nitrification rates of 945–1817 mg-N m^?2 d^?1 and 1124–1615 mg-N m^?2 d^?1 for light and dark experiments. When the minimum DO was 4.1 mg l^?1, the biofilm nitrification rates under light and dark conditions did not differ significantly at 95% confidence. When the minimum DO in the dim light experiment was 3.2 mg l^?1, the nitrification rates under light and dim light conditions were 945 mg-N m^?2 d^?1 and 563 mg-N m^?2 d^?1 and these significantly differed. Further decrease of DO to 1.1 mg l^?1 under dark conditions resulted in more decrease of the nitrification rates to 156 mg-N m^?2 d^?1. It therefore seems that under these experimental conditions, biofilm nitrification rates are significantly reduced at a certain point when bulk water DO is between 3.2 mg l^?1 and 4.1 mg l^?1. As long as bulk water DO under dark is high, light is not important in influencing the process of nitrification.     

Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor

Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent containing 1.0 mg Cr(VI) l^?1 at dilution rate (D) of 0.3 d^?1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l^?1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg Cr(VI) g^?1 DB. The system reached a specific metal removal rate of 458 μg Cr(VI) g^?1 DB d^?1, and a volumetric removal rate of 132 μg Cr(VI) l^?1 d^?1.