Agricultural sand filters

I’ll say this right away: many people still confuse industrial and agricultural filtration systems, but in vain. The difference is not in the particle size, but in the very logic of working with suspensions. When you see how deposits appear on drip irrigation within a week, you understand that standard mesh filters simply cannot survive here.

Why sand

We started with quartz sand with a fraction of 0.8-1.2 mm - it seemed like a proven option. But in field conditions, small particles of clay literally cemented this layer. I had to switch to a multi-layer backfill, where the bottom layer was 3-5 mm gravel. By the way, it was then that we began to cooperate withShandong Linyao Intelligent Agriculture Technology Co.,Ltd- their engineers suggested combining fractions depending on the water analysis.

Backwashing is a different story. If you do it less often than once every 10-12 days, the sand sinteres into a monolith. It was necessary to physically break these layers with crowbars at a facility in the Krasnodar Territory. Now I always install two pressure gauges - before and after the filter, to control the pressure drop.

Speaking of temperature: in winter, at -15°C, the flushing valves froze even with heating. They found a non-standard solution - they began to add an air compressor to the drainage line for purging. It’s a small thing, but it’s been working for three seasons without any complaints.

Typical installation errors

The most common is installation without a bypass. When the filter is washed, the entire system stops. This is critical in greenhouses with seedlings. We had to redo the piping right in the season, which is always stressful for both the crop and the agronomist.

Another point: many save on pre-filtration. And then they wonder whysand filtersrequire washing every two days. We install the simplest coarse mesh filters in front of the pumping station - and the sand resource triples.

The website https://www.lyzhihuinongye.ru has good piping diagrams for different types of water intake. We adapted them to our conditions - we left the option for manual washing when the automation fails. In field conditions, this is not a luxury, but a necessity.

Case: filtration for vineyards

In Crimea we are faced with high mineralization of water. The sand became clogged with carbonate deposits within a month. The solution was found throughShandong Lingyao Co.,Ltd- installed a system with acid dosing in front of the filter. But pH control is more important here, otherwise you can ruin both the filter media and the drip lines.

An interesting effect was noticed: after switching to multilayer filters, the frequency of cleaning droppers decreased. Although theoretically sand should not affect dissolved salts. Apparently, small organic suspensions that were not captured before are retained.

Now we are experimenting with adding a layer of zeolite - so far the data is contradictory. In some farms, filtration of organic matter has improved, in others, problems with backwashing have appeared. We need another season of observation.

Systems Design

When calculating productivity, we always include a margin of 15-20%. Not because the filters can’t cope, but because of uneven load. When several irrigation areas are turned on simultaneously, a pressure surge is guaranteed. It's better to be a little safe.

Colleagues fromShandong Lingyao Intelligent Agriculture Technologyoffer an interesting solution - a cascade of three filters with different sand fractions. But in practice, this is difficult to maintain under normal farming conditions. We settled on a two-stage system: coarse cleaning + fine cleaning.

An important nuance: when designing, drain lines for flushing are often forgotten. As a result, swamps form around the filters. Now we always lay drainage channels or pits with pumps.

Economics of content

Many people are afraid of high initial costs, but if you calculate the cost of equipment downtime due to clogged injectors, the picture changes. In the sugar beet industry, repairing one sprayer line costs more than a year of servicing a filtration station.

The sand needs to be changed every 2-3 years, but there is a trick: instead of buying a new one, you can wash and calcine the old one. We conducted such an experiment on the basis of https://www.lyzhihuinongye.ru - after heat treatment, the sand was almost as good as the new one in terms of characteristics.

We now consider it advisable to switch to automatic washing systems. For small farms this is still a bit expensive, but where the area is more than 50 hectares, it already makes sense. Especially when you consider the savings on personnel.

Non-standard applications

Fisheries have adapted sand filters to purify water in swimming pools. I had to reduce the fraction to 0.4-0.8 mm and increase the frequency of washings. But they abandoned expensive membrane systems.

Another interesting experience is its use in fertigation systems. It turned out that sand is good at retaining undissolved fertilizer particles. This is especially true for potassium sulfate, which often contains insoluble impurities.

We tried to install filters in front of sprinklers - the result is controversial. For central systems it is justified, but for individual machines it is redundant. Although the wear on pump bearings has actually decreased.

What's in the future

Now we are testing a system with water turbidity sensors - they give a signal to start washing. It’s still expensive, but it could become a standard for precision farming. Especially in projectssmart agriculture, where predictive repairs are important.

I see potential in the combination of sand filters with ultraviolet treatment. But the problem of organic films on quartz has not yet been solved - they reduce the efficiency of UV lamps. Perhaps some intermediate cleaning step is needed.

Overall,agricultural sand filters- far from being archaic, as some people think. You just need to understand their place in the technological chain and not expect miracles where other solutions are needed. The main thing is to adapt it to specific conditions, and not blindly copy other people’s schemes.