Session 8. Chemigation and Water Treatment for Microirrigation
Iron Control System for Drip Irrigation
Drip irrigation of 16 ha. of greenhouses, shade houses and field grown containers was accomplished using water containing up to 6.0 mg/l of iron. Crops were irrigated on a daily basis for 3 years without significant clogging problems.
The system designed and installed to control the iron problems consisted of the following components:
1. Gas Chlorinator-To allow consistent injection of chlorine in its most available and efficient form.
2. Hydrocyclone Containing Filtering Discs-To ensure complete and uniform mixture of the gas in the water within a limited space.
3. Sand Media Filters-To settle the oxidized iron and filter it from the water.
4. Back-up Disc Filters-To control filtration failures and complete iron separation.
Keywords: Drip irrigation, Filtration, Chlorination, Iron
Abstract taken from paper found on pages 239 to 243 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
Performance Evaluation of Filters and Emitters with Secondary Effluent
I. Ravina, E. Paz, G. Sagi, A. Schischa, A. Marcu, Z. Yechiely, Z. Sofer, Y. Lev
Seasonal surface reservoirs storing secondary effluent are a major source of irrigation water in Israel. Operational difficulties, associated with plugged emitters and/or filters have occurred frequently in drip irrigation systems using these waters. In an attempt to solve these problems, field trials were conducted in which various types of commercially available emitters and filters were tested under controlled conditions. The trials were conducted successively with water supplied from two types of reservoirs. In 1987-1990, from a shallow reservoir containing a blend of secondary effluent and fresh water (Kfar Baruch) and since 1991 from a deep reservoir storing only secondary effluent (Burgata). The experimental set up consisted of a filter testing platform and emitter testing systems operating in parallel. The performance of the various emitters and filters and the effectiveness of water treatments were evaluated using data obtained from continual measurements of flow rates and pressures in the systems. The main factors causing the clogging problems have been development of biomass of mucous organisms (colonial protozoa in Kfar Baruch and sulfur bacteria in Burgata) and flocculation of suspended, clay and silt, particles with algae. There was no difference between the emitter performance with water filtered to a level of 80 mesh (180 m m) and its performance with water filtered to a level of 120 mesh (125 m m). But, there was a large difference between the clogging rates of the secondary filters at these two filtration levels. Hence, it has been recommended to use check filters of 80 mesh for water reuse in drip irrigation systems. There were definable differences between granular media, disc and screen filters as to their ability to protect a downstream check filter or drip emitters. There were definable differences between emitters of various types as to their sensitivity to clogging. Chlorination was found to be the key for keeping the drip irrigation system free of clogging problems when using secondary effluent.
Keywords: Drip irrigation; Filtration; Water treatment; Biological fouling; Sewage
Abstract taken from paper found on pages 244 to 249 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
Clogging of Drip Irrigation Systems by Colonial Protozoa and Sulfur Bacteria
G. Sagi, E. Paz, I Ravina, A Schischa, A. Marcu, Z. Yechiely
Growth of colonial protozoa (Epystilys balanarum) and sulfur bacteria (Beggiatoa alba) within the irrigation systems were the main reason for emitters clogging in Israel. Fouling by these organisms took place within all the components of the irrigation systems which included the transmission lines, the filters, the laterals and drip emitters, regardless of the material of the component (e.g. metal or plastic).
Colonial protozoa developed in a wide variety of surface water quality, while sulfur bacteria grew only in water which contained sulfide (H2S). Chlorine injection is the most common method used in the field to prevent clogging by colonial protozoa and sulfur bacteria and for the restoration of blocked irrigation systems. In the experimental study, chlorination every other week, at a concentration of 10 mg/L for 1 hour, prevented clogging of the drip emitters by colonial protozoa. Chlorination for 1 hour prevented clogging by sulfur bacteria, but only when the interval between treatments was shorter than 3 days.
Keywords: Drip irrigation Colonial protozoa Sulfur bacteria Sulfide Emitter clogging
Abstract taken from paper found on pages 250 to 254 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
Hydraulic Characteristics of an Economical By-pass Injector for Microirrigation
Mhammed Larhrafi and Soichi Nishiyama
For the purpose of chemical injection into microirrigation systems, hydraulic characteristics of a low cost and low energy by-pass chemical injector operating on the basis of the pressure head differential generated between the inner and outer walls at the midpoint of a bend were clarified. A general equation to determine the pressure head differential across a bend is presented. The by-pass flow rate and main flow discharge relationship was found to be linear. The results of this study showed that the by-pass flow depends not only on the available head differential across the bend, but also on the by-pass inlet and outlet orfice size. An equation to predict the by-pass as a function of the bend geometric characteristics and the available head differential is proposed. The use of such injectors will contribute to saving energy and reducing farming operations costs.
Keywords: Microirrigation, Chemigation, Injector
Abstract taken from paper found on pages 255 to 261 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG