The effect of microorganisms, salinity and turbidity on hydraulic conductivity of irrigation channel soil

Abstract

The introduction of polysaccharide producing benthic algae and bacteria could provide a low cost technique for seepage control in irrigation channels. The ability of algae and bacteria to produce polysaccharides proved to be successful in reducing the hydraulic conductivity of irrigation channel soil. Hydraulic conductivity was reduced to less than 22% of its original value within a month of inoculating soil columns with algae. Chlorophyll and polysaccharide concentrations in irrigation channel soil were measured in order to assess the growth of algae and extent of polysaccharide production, and their correlation with hydraulic conductivity of channel soil. Increases in polysaccharide occurred in the top layer (0-5 mm) of the soil column. The reduction of hydraulic conductivity was highly correlated with the amount of polysaccharides produced (r2=0.92). Hydraulic conductivity decreased with increasing algal and bacterial numbers. The first few millimetres of the soil core where microbial activity was concentrated, seemed effective in controlling seepage. Incorporation of extra nitrate and phosphate into algal medium did not increase the production of polysaccharides by algae in channel soil. The effect of salinity and turbidity of irrigation channel water on channel seepage was studied by measuring the effects on hydraulic conductivity of channel soils. When the electrical conductivity (EC) of the water increased above a threshold value, the hydraulic conductivity increased because of the flocculating effects on clay particles in channel soils. A relationship between sodium adsorption ratio (SAR) and EC of the channel water was established which indicated 15% increase in channel seepage due to increases in salinity. Increasing the turbid-S. R. Ragusa ([]) 9

Biological, chemical and physical factors influencing the seasonal change of polysaccharide concentration in irrigation-channel sediment

“…The increase in polysaccharide concentration with increasing number of algae -a result obtained from a previous experiment (Ragusa et al, 1994) -is well supported by these field results. Since we found that the hydraulic conductivity of channel sediment was negatively correlated to polysaccharide concentration (r= -0.96, P<0.001) (Ragusa et al, 1994), fluctuations in polysaccharide concentration in irrigationchannel sediment would affect the rate of seepage from these irrigation channels.…”

“…By hydrobiological examination of artificial-recharge reservoirs, Moravcova (1971) found that clogging of the reservoir bottom was connected with heavy growth of algae. In laboratory studies, Ragusa et al (1994) showed that hydraulic conductivity was negatively correlated to polysaccharide concentration (r= -0.96, P<0.001) in the top 5-mm layer of the soil core. Polysaccharide concentration increased with increasing algal and bacterial number in this layer.…”

Irrigation Water Quality Standards for Indirect Wastewater Reuse in Agriculture: A Contribution toward Sustainable Wastewater Reuse in South Korea

“…A high level of turbidity can affect the performance of the irrigation facility, and can lower the hydraulic conductivity of the soil and in turn pollute the soil surface through surface flow [68,69]. In addition, since various viruses and bacteria can be attached to and migrate along with the solid particles, the elimination of suspended solids is related to the elimination of germs [33].…”

The influence of hydraulic loading on biofilm properties in a subsurface wastewater infiltration system

“…The polys accharide content of biofi lm was quantifi ed using Ragusa et al (1994). Each fi ller particle was removed from the system and placed in glass reaction tubes of the same size.…”