Gideon Oron

Duckweed culture for wastewater renovation and biomass production

Outdoor experiments were conducted in shallow mini-ponds (20 and 30 cm deep) for evaluating the performance of the duckweed species Lemna gibba as a purifier of domestic wastewater. It was found that under adequate operational conditions, the quality of secondary effluents meets irrigation reuse criteria. The annual yield (dry matter) of duckweed, harvested two to three times a week, is about 55 ton/ha, with a protein content of 30%. Hence, by cultivating duckweeds the ammonia in ponds for domestic wastewater treatment is converted into valuable protein rich biomass which subsequently can be used for animal feed or agricultural fertilization. The economic benefit of the additional by-product of the biomass reduces wastewater expenditures in the range of 0.020 to US

Poliovirus distribution in the soil-plant system under reuse of secondary wastewater

0.050 per each treated m3 of wastewater.

Removal of viruses from surface water and secondary effluents by sand filtration

Abstract Treated domestic wastewater is a source of water utilized for a variety of purposes. Outdoor experiments were conducted to examine poliovirus penetration into tomato plants under subsurface drip irrigation with secondary level treated domestic wastewater. According to the results, high virus content in the applied wastewater resulted in a limited penetration into the plant via the roots. No virus contamination was found in the leaves of plants irrigated with wastewater spiked with viruses, while a limited amount of virus contamination was detected in leaves of plants irrigated with tap water enriched with poliovirus.

Surface properties and reduced biofouling of graft-copolymers that possess oppositely charged groups.

The filtration of phi X 174, MS2, and T4 bacteriophages out of tap water and secondary effluents was performed by rapid sand filtration. The viruses were characterized, and the influence of their microscopic characteristics on filterability was examined by comparing retention values, residence times, attachment, and dispersion coefficients calculated from an advection-dispersion model and residence time variation. The only factor observed to influence retention was virus size, such that the larger the virus, the better the retention. The difference was due to the more effective transport of viruses inside the media, an observation that runs counter to currently accepted filtration theory. Cake formation on top of the filter during the initial stages of secondary effluent filtration significantly increased headloss, eventually resulting in shorter filtration cycles. However, deep filters contain buffering zones where the pressure drop is amortized, thus allowing for continued filtration. After the effluent passed through the buffer zone, regular filtration was observed, during which considerable virus retention was achieved.

Improved saline-water use under subsurface drip irrigation

Microbial biofilms and their components present a major obstacle for ensuring the long-term effectiveness of membrane processes. Graft polymerization on membrane surfaces, in general, and grafting with oppositely charged monomers, have been shown to reduce biofouling significantly. In this study, surface forces and macromolecular properties of graft copolymers that possess oppositely charged groups were related to their potent antibiofouling behavior. Graft polymerization was performed using the negatively charged 3-sulphopropyl methacrylate (SPM) and positively charged [2-(methacryloyloxy)ethyl]-trimethylammonium (MOETMA) monomers to yield a copolymer layer on polyvinylidene fluoride (PVDF) surface. Quartz crystal microbalance with dissipation monitoring (QCM-D) technology was used to monitor the reduced adsorption of extracellular polymeric substances (EPS) extracted from a membrane bioreactor (MBR) wastewater treatment facility. Complemented measurements of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy provided evaluation of the antifouling properties of the surface. Increase in water content in grafted layer exposed to 100 mM aqueous NaCl solution was observed by QCM-D. Therefore, the grafted copolymer layer is swelled in the presence of 100 mM NaCl because of reversing of polymer self-association by counterions. Force measurements by atomic force microscopy (AFM) showed an increased repulsion between a carboxylate-modified latex (CML) particle probe and a modified PVDF surface, especially in the presence of 100 mM NaCl. The hydration and swelling of the grafted polymer layer are shown to repel EPS and reduce their adsorption. Delineating the surface properties of antifouling grafted layers may lead to the design of novel antifouling surfaces.

Greywater use in Israel and worldwide: standards and prospects.

Abstract The scarcity of fresh water in arid regions makes saline water a valuable alternative water source for irrigation. Although saline-water use for agricultural irrigation is associated with some reduction in the yield, it is coupled with improved yield quality, as expressed by higher total soluble solids content. Field experiments which are in progress in a pear orchard verify that under subsurface drip irrigation (SDI) with saline water, reasonable yields can be obtained. Moisture and salinity distribution under SDI are better adjusted to the root pattern in the soil, in comparison with the conventional drip irrigation (DI). These distribution patterns explain, to some extent, the reaction of trees to saline-water application.

Nitrogen removal and conversion by duckweed grown on waste-water

Water shortage around the world enhanced the search for alternative sources. Greywater (GW) can serve as a solution for water demands especially in arid and semi-arid zones. However, issues considered which include acceptability of GW segregation as a separate water treated stream, allowing its use onsite. Consequently, it is the one of next forthcoming water resources that will be used, primarily in the growing mega-cities. It will be even more rentable when combined with the roof runoff water harvesting and condensing water from air-conditioning systems. Reuse of GW is as well beneficial in the mega-cities subject to the high expenses associated with wastewater and fresh water conveyance in the opposite direction. The main problem associated with GW reuse is the quality of the water and the targeted reuse options. At least two main options can be identified: the public sector that is ready to reuse the GW and the private sector which raises extra issues related to the reuse risks. These risk stems from the on yard use of GW, relatively close to the household location. The main focus of the Israeli guidelines for GW use is on the private and single house. The problem is less rigorous in public facilities, where the amounts are relatively large and the raw GW is relatively diluted. The two main principles adopted for reuse are: (i) greywater can be minimally treated since it differs from the black wastes, and; (ii) no contact exists with the resident around. The aggravated standards are an indication of the sensitivity issues related to the problem.

Current status in wastewater treatment, reuse and research in some mediterranean countries

Abstract Duckweed was grown in outdoor ponds for the purpose of domestic waste-water treatment, recycling of the nutrient and effluent renovation. Growth of the plant was examined at two pond depths and various hydraulic retention times. Temperature stratification in the ponds probably affected ammonia uptake. Dry yield of the duckweed approached 15 g m−2 day−1 with a protein content of about 30% in the short retention-time treatments. Effluent quality was at the secondary level and met criteria for re-use for agricultural irrigation.

Optimal operation of a multisource and multiquality regional water system

AbstractThe status of treated wastewater reuse as experienced in some Mediterranean Basin countries such as Greece, Israel, Italy and Cyprus is examined. General background information is given for each of these Mediterranean countries, including natural water resources, climatic conditions (temperature, rainfall), generated wastewater, crops cultivated and irrigated with effluent, and related aspects of reuse. The examined parameters include treatment strategies, wastewater reuse standards applied in each country, effluent reuse research in progress in the above target countries related to the treatment technologies, water quality, regulations, economics, public acceptance, risk assessment, benefits, keys for potential success and main constraints. Emphasis has been given to the benefits of treated wastewater reuse in integrated water resources management systems and its role for water cycle management, solving water scarcity issues mainly in arid and semi-arid regions of the Mediterranean basin. The exp...

Simulation of water flow in the soil under sub-surface trickle irrigation with water uptake by roots

A mathematical model for optimal real-time operation of a regional water system was developed and examined. The regional system consists of numerous water sources with various water qualities and a variety of consumers with different flow and quality requirements. In order to satisfy the different consumer constraints, nodal flow and solute balances were defined. Pump and valve-on and valve-off situations were defined by continuous nonlinear equations. The model was solved numerically for a short time period by a projected Lagrangian method for the water supply system in the Arava Rift Valley, Israel. The global uniqueness of optimal solution was proven