Using organic fertilizer to mitigate organic-inorganic fouling in agricultural saline wastewater irrigation systems

Recycling saline wastewater for agricultural irrigation offer a promising solution to address both water scarcity and anthropogenic pollution. However, organic-inorganic fouling in saline wastewater irrigation systems (SWIS) poses significant technical and economic challenges. Traditional chemical biocides are currently insufficient for controlling composite organic-inorganic fouling and may pose environmental hazards. This study proposed a greener approach using organic acid (OA) fertilizers to alleviate organic-inorganic fouling in agricultural SWIS. The treatment performances were assessed employing four types of OA fertilizers (i.e., humic acid, alginic acid, nucleotide, and ammonia acid) and a negative control. Results showed that three types of OA, i.e., alginic acid, nucleotide, and ammonia acid, effectively reduced the total SWIS fouling content by 11.2%-57.4%, whereas humic acid exacerbated fouling by 11.2%-57.4%. Specifically, all types of OA significantly mitigated the content of inorganic fouling (precipitates and silicates) by 10.7%-42.3% by forming loosed and sparser structures. However, OA exhibited minimum effects on controlling silica fouling. Meanwhile, except the humic acid, other types of OA decreased the total content of organic fouling by 17.2%-39.5% by reducing the content of humic substances and building block fractions. In addition, the significant binary interactions of organic-inorganic fouling indicated the active role of calcium silica and biomineralization fouling. These findings provide insight into the development of appropriate and eco-friendly antifouling strategies for SWIS, with implications for recycling and reusing saline wastewater.

Performance of disc, conventional and automatic screen filters under rainbow trout fish farm effluent for drip irrigation system

This study aims to investigate the performance of disc, conventional screen, and automatic screen filters when rainbow trout fish effluent is used for irrigation. The experiments were performed in a fish farm, located in the north-west of Iran. The disc and conventional screen filters were tested at pressures of 150 and 300 kPa, and the automatic screen filter at 200 and 300 kPa. The filtration experiments continued until the backwashing was reached. The results showed that (1) the initial head loss of disc and conventional screen filters was 40 kPa, while for the automatic screen filter was 5 kPa. (2) In the disc filter, with increasing working pressure, the filtered volume significantly (P < 0.05) increased from 9.7 to 14.5 m³ m^-2 (10 kPa)^-1, but for conventional and automatic screen filters, it was constant at 5.5 and 7.0 m³ m^-2 (10 kPa)^-1, respectively, and all of them had significant (P < 0.05) differences. (3) In the disc filter, with increasing the working pressure, the filtered volume to reach backwashing significantly (P < 0.01) increased from 80.9 to 104.4 m³ m^-2, while in the conventional screen filter increased from 14.1 to 16.4 m³ m^-2. This volume at two working pressures was 29.5 m³ m^-2 for the automatic screen filter. These volumes were significantly different (P < 0.01) between filters. (4) The mass retention for the disc, conventional, and automatic screen filters were 28.88, 9.11, and 7.72 g min^-1 m^-2, respectively, and tended to increase at lower working pressures. Based on this index, the difference in the performance of the filters was significant (P < 0.01). (5) Overall, the best performance was for the disc filter, and after that was the automatic screen filters, but the period of time to operate for the filters until backwashing time was less than half an hour, which is not applicable under farm conditions.

Electrochemical biofilm control by reconstructing microbial community in agricultural water distribution systems

Biofilm causes considerable technical challenges in agricultural water distribution systems. Electrochemical treatment (ECT) is a potential technique for controlling biofilm in the systems. Given the limited information on how ECT performance changes of irrigation systems and microbial biofilm community shifts. In this study, the effect of anti-biofilm was assessed. Illumina Miseq high-throughput sequencing, combined with molecular ecological network analysis, were applied to detect the effects of ECT on attached biofilm microbial communities. We found that ECT effectively mitigated biofilm formation with the fixed-biofilm biomass reduced by 37.5 %-79.9 %. ECT significantly shifted the bacterial community structures in the biofilm, reduced the communities' diversity, and changed the dominant species. Molecular ecological network analysis showed that the complexity and size of bacterial networks were destabilized under ECT and decreased the interactions among bacterial species. The reconstruction in bacterial community and networks were responsible for the decline in extracellular polymer substances and biofilm biomass. However, chlorine-resistant bacteria were found increased after ECT, and higher relative abundance and low biofilm removal was identified in continuous ECT as compared with intermittent ECT. These results aimed to highlight the opportunity for biofouling mitigation by ECT for irrigation systems, and reveal the potential anti-biofilm microbial mechanisms of ECT.

Using electromagnetic fields to inhibit biofouling and scaling in biogas slurry drip irrigation emitters

Reusing biogas slurry (BS) in agricultural drip irrigation systems may provide a solution to deal with the adverse environmental impacts of applying BS. Biofouling and scaling are two leading issues in drip irrigation emitters. This study investigated a practice that applied electromagnetic fields (EMFs) to control biofilms and scales. The bacterial communities and mineral precipitations in the clogging substances of emitters were determined. Results showed that EMFs inhibited the growth of microbes, and influenced BS physicochemical parameters. Consequently, EMFs shifted the bacterial communities with reduced diversities. Network analyses revealed that bacterial species under EMFs treatments showed lower average connectivities and simpler interactions, which were responsible for the decreases of extracellular polymers substances (EPS). Moreover, EMFs treatments not only reduced the carbonates in emitters, but also prevented the depositions of phosphates, silicates, and quartzes. EMFs also had impacts on the lattice parameters and crystal volumes of carbonates. In addition, the changes in bacterial communities and EPS contents were associated with the reductions of various minerals. Accordingly, EMFs effectively mitigated biofilms and scales with the fixed clogging substances reduced by 29.1-53.8 %. These findings demonstrated that applying EMFs is an effective anti-biofouling and anti-scaling treatment with potential applications in BS irrigation systems.

Clogging investigation of pressure compensating button emitters: an experimental study of four types

Drip irrigation is of prime importance from several points of view as the most effective and reliable method. Nevertheless, emitter clogging is the major problem related to this technology. Furthermore, pressure compensating button emitters are widely used considering their advantages resulting from the uniform distribution of water, reduction of evaporation, and deep percolation. In the present study, we report on four pressures compensating button emitters and their resistance to the clogging. Our research objectives incorporate two aspects; executing a 980-h experiment of drip irrigation by taking into consideration the temperature calibration equation, and evaluating the performance of the emitters by using the following four parameters: the relative average discharge (Dra), coefficient of uniformity (CU), emitter uniformity (EU), and the flow rate variation (q_var). Thus, analyzing the evaluation of those parameters provides the potential of choosing emitters that have a high resistance to the clogging. The main conclusion of this research effort is that three types of the four emitters display a satisfactory resistance to clogging.

Methodology for hydraulic characterisation of the sand filter backwashing processes used in micro irrigation

The correct operation of the backwashing process in sand filters used in micro irrigation determines directly the effectiveness of the subsequent filtration processes, and consequently the micro irrigation systems maintenance. As backwashing involves the filter bed expansion, the current sand filter design makes it impossible to measure the process. In this sense, this work aims to present a hydraulic characterization methodology of the backwashing process of sand filters used in micro irrigation, evaluating the influence of the sand particle size, the filter bed height, and the sand filter design. The proposed methodology can assist manufacturers in gathering equipment operating information, aiming at its presentation in the product catalogs.•This method article discusses a method of hydraulic evaluation of the backwashing process of sand filters used in micro irrigation.•The method can assist sand filter manufacturers in the correct definition of the equipment's operating parameters.•The method shows the effectiveness of using the filter media pressure loss evaluation in the indirect definition of the minimum fluidisation velocity.