Personal tools
You are here: Home Knowledge center Case histories Biological treatment of agricultural effluents
Document Actions

Biological treatment of agricultural effluents

BIO-SYSTEMS SA treats a mixture of agricultural effluents

Case history 1: how a piggery problem was solved

Mark Tutton owns a small pig farm in Klipheuvel near Cape Town. Both he and his pigs enjoy excellent health and he declines the use of antibiotics and similar additives. In spite of his prospering business, a cloud in the form of muttering neighbours began to darken his horizon. The reason? Pig effluent.

He had been running his waste wash water into a large septic tank from where some soaked into the soil. The surplus was pumped via a 75mm plastic pipe some 500m to a neighbour's kikuyu meadow. Increasingly bordering smallholders complained of pig scented water in their boreholes and of an escalating porcine reek drifting on the breeze.

CH: pig problem solved  Mark Tutton with his pigs

A CMC health Inspector analysed the effluent. Mark did not score well. BIO-SYSTEMS SA, who had assisted other farmers in similar predicaments, was called to offer suggestions. It was really a very simple problem to solve and it cost mere peanuts!

First the effluent. We made the 24m3 septic tank into a treatment pump station and inoculated it with 500g of our B800 microbial seed. Within three days the odour had diminished. We recommended Mark reduce his water consumption to a minimum and that he pump out the sump three times a week. But there was still a problem with odour build-up in the sties. Because 'degreasers' and strong detergents could not be used (health hazards etc.), lots of water was needed to wash out all the droppings, urine and food scraps. This time consuming operation was a prime cause of overload on the system.

Unfortunately, however, this method was unsuccessful in removing the ammonia build-up that was causing the neighbours to choke on their sundowners. BIO-SYSTEMS recommended our Hard Surface Degreaser (HSDG). This remarkable product loosens all hydrocarbons (natural constituents of droppings, urine and food) and encapsulates the molecules allowing harmless disposal via the pump station and out into the environment, via the irrigation – keeping the pipeline purged as well.

By using a combination of B250 and HSDG within two weeks, the odour had gone, the quality of final effluent had improved (see Fig 1) and Mark was welcome once again on all the neighbouring stoeps at cork out time.

Mark now runs on 250g of B250 per 6 weeks and 5lt of HSDG per fortnight. The cost? Less than R500 a month.

Figure 1:


Before
After
COD
17,334
1,170
Ammonia
353
0.4
Conductivity [ms/m]
458
125


Case history 2: the biological treatment of mixed agricultural effluent

Modern farming methods have done wonders for modern man. Not only do we now enjoy excellent quality meat, but the farmer is more assured of reliable results and prices.

However, in his pursuance of the Perfect Pig, Farmer Giles has Achillesed his heel with the Perfect Pooh. To raise pigs that are 90kg dry weight, they are fed a selected diet containing medications which pre-empt the animal succumbing to a variety of common ailments that would otherwise disturb the programmed weight gain process. These antibiotics render their waste virtually sterile, biologically 'dead'. Instead of breaking down, it becomes a source of odour.

Such a case developed just outside Cape Town where a local pig farmer was faced with the nagging problem of a gradually deteriorating slurry lagoon of some 5,000m3 capacity. It was being progressively overloaded as the demand for his good quality table pork and bacon increased. In line with increasing activity, porcine odours were beginning to become a nuisance, whilst the untreated pig slurry was finding its way into the natural watercourses on the farm.

BIO-SYSTEMS SA was asked to make suggestions for the treatment of the effluent. Within a short time a considerable improvement was achieved to the satisfaction of all parties concerned, not least of these being the Department of Water Affairs and Forestry (DWAF).

The enterprise enjoys a highly public 'open farm stall' ambiance comprised of piggery, dairy, bacon factory, farm shop, accommodation hostel and houses, plus various peripheral activities. Construction of two new lagoons of 6,000m3 each commenced and an existing irrigation (surface runoff) storage dam was prepared as a reservoir for winter storage.

The old (long dormant) pig sties were increasingly repopulated as the production of baconers increased. Like many similar enterprises, the sties use the 'wet drive' method of faecal removal: floors are flushed down and the channels emptied into the lagoon on a weekly rotation basis.

This activity was somewhat hampered by the sawdust and wood shavings used as a bedding compound. Economically attractive at the procurement end, this material leads to increasing disposal problems and requires expensive methods for its further management. However, we achieved a meaningful degree of success and this is how it was done:

  1. The concrete floors of the pens were hand-pump sprayed with our Hard Surface Degreaser (HSDG) each time the broods were moved. This drew the ammonia build-up from urine out of the concrete and harmlessly encapsulated it, greatly reducing respiratory distress and reducing 'the pig smell' to a minimum. 
  2. The wet drives were inoculated each week with our microbial blend B800, which boosted the break down of COD initiated by the reduced latent bacteria within the slurry. This ensured the suppression of anaerobic conditions and prevented the consequent production of sulphide gases. It was most encouraging that the sties smelled so sweet; even the farm visitors commented on the lack of smell.


When BIO-SYSTEMS was asked to get involved, the lagoon was largely crusted with floating and semi-submerged solids (as the picture shows). Largely anaerobic, foul smelling gasses frequently 'burst' to the surface. The effluent quality was very poor with a COD averaging 15,000mg per litre.

On a trial basis, we installed one of our portable 220v, 0.75Kw AirMix Aeration Injectors, designed and assembled by Pumps Unlimited, and inoculated with BIO-SYSTEMS B250. The microscopically fine entrained air injected into the effluent (having been first drawn from the lagoon) provided a natural microbial catalyst and assisted the aerobic organisms to out-compete the sulphide-forming anaerobes.

Within a week, the surface scum was reduced and the COD values began to fall sharply. Odours ceased and after six weeks the COD at the outlet of the lagoon was down to 600mg per litre.


CH: effluent streams - lagoon before treatment  Before BIO-SYSTEMS treatment


The overflow passed to the secondary and tertiary lagoons via ‘T siphons’, the combined capacity permitting sufficient residence time for the degradation of COD down to 200mg per litre (irrigation standard) before the open channel sluit to the reservoir. The dosing regimen of B250 into both the wet drives and lagoon was adjusted to the load, weekly COD readings being the deciding factor.

A problem was experienced with the sawdust bedding litter. This material, swollen by having soaked in water, caused blockages in the pump and a heavy-duty grinder pump was specified.


CH: effluent streams - lagoon with AirMix Aerator  After BIO-SYSTEMS treatment


The performance of the disposal system could be considerably improved by using a 1.7kW  AirMix infusion aerator in the primary with a 0.9kW unit in the secondary lagoon, but the BIO-SYSTEMS product, hardened to withstand a certain degree of biocide activity, is the joint key to success. Happily, this technology augments nature's natural processes, plus it’s simple and surprisingly low in cost. No harsh chemicals are used and the resultant effluent quality meets with both local (DWAF) and international requirements.

Capital expenditure for the AirMix and the initial 'shock dosing' was within R30 000. Maintenance dosing was running at under R1 500 per month. For the size and complexity of the enterprise served, this was petty cash.


Finally, by using one of our Spill-SorbTM peat polishing filters, re-used water for washing down could certainly be achieved and the eventual refinement to potable drinking water is within economic bounds.

Related content


www.bikalabs.com - Home of Bika Lab Systems -  Plone hosting, content management systems and open source LIMS