Design of Land Application Systems for Water Reuse

Water reuse via land application is old technology; but the water balance only design approach and practice has not worked well. There are many benefits of water reuse by irrigating crops; however, there are some risks if not designed properly. When the design approach uses a combined water-nutrient-salt balance, the most effective and sustainable, long-term system is achieved. This approach provides a design based on land area requirements, on-site water storage, and economic return from the irrigated crops. The single, most often overlooked step in the water balance is accounting for the water stored in the soil. When spread over large areas, this quantity of water results in considerably less required surface water storage, which saves capital costs. This design approach has been used successfully on multiple sites for over 30 years without failure.

Effective Adsorption of Nutrients from Simulated Domestic Sewage by Modified Maifanite

Modified maifanite (MMF) was prepared by synthesized method with sulfuric acid treatment and high temperature calcination, and evaluated as an effective adsorption material to remove the nutrient salt in waste watery. Compared with the raw maifanite (RMF), the MMF exhibited the higher adsorption capacity and higher removal efficiency. The results showed that the adsorption rates of total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH3-N), nitrate nitrogen (NOx-N) and Chemical Oxygen Demand (COD) by MMF (RMF) were86.7% (76.7%), 44.9% (34.5%), 29.1% (20.8%) and 79.8% (13.0%) respectively at 20 ℃ for 24 h. MMF kept the basic structure and composition of maifanite with stronger surface roughness and more adsorption active sites. This study suggests that MMF can be further applied to treat domestic sewage and eutrophic water.

A Strengthening Mechanism and Influencing Factors of Coal Fly Ash using Microbial-Induced Carbonate Precipitation

Coal fly ash (CFA) that is discharged from coal-fired power plants has characteristics of fine particles, a small specific gravity and a large pore ratio. The dust suppression and strengthening of CFA is usually carried out by spraying water in the ash storage yard, but this practical approach is unsatisfactory. The strength of the CFA filling material affects the construction safety and operational safety of the ash dams. To carry out effective CFA material utilization and dust-pollution control, this paper applied the microbial-induced carbonate precipitation (MICP) method to enhance the strength of CFA under two curing conditions of natural evaporation (NE) and in a moisture cylinder (MC). The microbial-reaction mechanism, strengthening characteristics and influencing factors were studied. The results show that: 1) the calcium carbonate that is produced by microorganisms in the CFA is calcite, and the calcium-carbonate content increases from 7% to 18.9% and 15.3% under the MC and NE curing conditions, respectively; 2) MICP can improve the CFA strength, and the unconfined compressive strength can be increased by 6.55 times to 97.63 kPa under the MC curing conditions; 3) the solidification strength of CFA varies significantly with the concentration of CaCl2.2H2O and CH4N2O nutrients. The peak stress increases initially and then decreases with an increase in nutrient salt concentration. The optimum nutrient concentration was 0.5 mol/L and 1.0 mol/L for the MC and NE curing conditions, respectively; 4) calcium carbonate that was induced by microbial reaction can reduce the water loss in the ash specimen, and allow the ash surface to form a better water-retention effect, with good prospects for dust suppression.

High Productivity Makes Mangroves Potentially Important Players in the Tropical Silicon Cycle

Over the last two decades, recognition of the important role terrestrial plants play in regulating silicon (Si) cycling has emerged. Si improves plant fitness by protecting them from abiotic (e.g., desiccation) and biotic (e.g., fungal attack) stressors. Once incorporated into plant biomass this biogenic Si is more bio-available than the lithogenic material from which it was ultimately derived. Thus plants play a key function in regulating the amount and timing of Si availability in downstream ecosystems. Recent work has highlighted the importance of salt marshes in the temperate Si cycle. However, the role of their tropical counterparts, mangroves, has largely gone unexplored. Here we report foliar concentrations of plant Si (as %Si by dry weight) for four Caribbean mangrove species: Conocarpus erectus (buttonwood), Laguncularia racemosa (white mangrove), Avicennia germinans (black mangrove), and Rhizophora mangle (red mangrove). Overall, the median Si concentration was low (0.07%) and did not vary among plant part (e.g., foliage, twig, and propagule). There was also little variation in Si among species. Using literature values of aboveground net primary production, and the concentrations reported here, we estimate an aboveground mangrove Si uptake rate of 2–10 kg Si ha–1 year–1. These rates are on par with rates reported for temperate and boreal forests as well as low nutrient salt marshes, but lower than estimates for high nutrient salt marshes. Thus, despite the low Si concentrations observed in mangroves, their high productivity appears to make them a hot spot of Si cycling in tropical coastal systems.

Distribution of Nutrient Salts and Chlorophyll-a in Surface Water along the Gulf of Aden and Arabian Sea Coast, Yemen

The distribution of inorganic nutrient salts (ammonium, nitrite, nitrate, phosphate and silicate) and phytoplankton chlorophyll-a (Chl-a) were investigated in the Gulf of Aden and along the Arabian Sea coast, Yemen. Seventy two surface water samples were collected during cruises in August 2014 and January 2015. The sampled area extends from As Suqayyah in the west of the Gulf of Aden to Hawf in the east. The study showed that the average values of nutrient salts (μg/l) in waters collected in August 2014 and January 2015 were 0.83 and 0.60, 10.98 and 10.03, 16.41 and 14.73, 10.36 and 8.76, and 29.72 and 22.67 for ammonium, nitrite, nitrate, phosphate and silicate, respectively. The average values of Chl-a (mg/m3) in August 2014 and January 2015 were 0.26 and 0.21, respectively. The results showed that nitrate levels were very high but those of ammonium very low. This may reflect the oxidation of ammonia to nitrite and then nitrate, leading to a very favorable ratio of ammonia and nitrate values. The low levels of dissolved inorganic nitrogen (DIN)compounds, (ammonium, nitrite, and nitrate), phosphate, silicate and Chl-a indicated that the southern coast of Yemen is not in a eutrophic condition. The highest nutrient salt values were in the eastern part of the study area, and may have resulted from water originating from the Indian Ocean and upwelling. Statistical analysis to seek correlations between nutrient salts and Chl-a show very good to excellent correlation, which may be due toconstant coastal environment.

The First Steps in Examining of Carbon Absorption and Nutrient Salt Filtering Capability of Rhodomelaceae Laurencia Papillosa Seaweed over Some Typical Island Communes in Vietnam Coastal Area

Viet Hai is a commune in Cat Hai district, Hai Phong City. The commune is located in the East of Cat Ba island which is the third largest island in Vietnam. Nhon Chau is also an island commune which is located in Quy Nhon city, Binh Dinh province. Nam Du commune is one of four island communes of Kien Hai district, Kien Giang province, and located at 120 kilometers away from the Rach Gia city. The results showed that the averaged values of nutrients absorbed by Rhodomelaceae Laurencia Papillosa in 12 hours were 1.39µg/l/day (N-NO2-); 11.74µg/l/day (N-NO3-); 24.08µg/l/day (N-NH4+); and 7.83µg/l/day (P-PO43-) in Viet Hai commune. In Nhon Chau island commune, the averaged values of nutrients absorbed in 12 hours were 1.25µg/l/day (N-NO2-); 7.44µg/l/day (N-NO3-); 11.81µg/l/day (N-NH4+); 23.53µg/l/day (P-PO43-), respectively. In Nam Du island commune, the nutrients absorbed in 12 hours reached the values of 23.4µg/l/day (N-NO2-); 15.3µg/l/day (N-NO3-); 101.65µg/l/day (N-NH4+); 30.32µg/l/day (P-PO43-), respectively. The average values of carbon absorbed by seaweed biomass in Viet Hai, Nhon Chau, and Nam Du communes were 30.27mgC/m2/h, 31.31mgC/m2/h, 33.00mgC/m2/h, respectively.