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Effluent streams sorted

The best way to dispose of both liquid and solid wastes

A ‘boutique’ farm in the peri-urban zone close to a large metropolis was experiencing problems with the disposal of both liquid and solid wastes. The farm in question comprised over 300 acres and bordered a national road near a busy junction. It was ideally placed to sell produce through a ‘farm stall’.

The eldest daughter of the family-run enterprise was a true entrepreneur. Under her influence her parent’s original activities of vegetable and wine production had been expanded to include a pedigree dairy herd (which was used to supply a small cheese factory specialising in ‘soft’ cheeses), a 150-sow-unit piggery as well as a small manufacturing delicatessen and speciality butchery, started by her Italian husband.

The same daughter expanded the timber shed farm stall, erected by her father in the 1980s, into a virtual country market. The farm stall housed a coffee bar, small restaurant, garden nursery and a few small pens housing a number of typical farm animals - such as, chickens, pigs, sheep etc - which the visitors and their children could ‘touch’ and ‘smell’ when they came to buy the variety of goods on offer. A gypsy violinist and a gallery where local folk could exhibit their arts and crafts added to the cultural ambience.

On the whole, it was a very successful and inviting attraction in an otherwise mundane part of the countryside. There was one big problem, however. The farm stall began to stink. What’s worse, it got really bad on summer afternoons. So bad, in fact, that people began complaining, especially those dining in the restaurant where flies became a pest.

BIO-SYSTEMS was asked to investigate and advise, which we did on a consultancy basis. We identified the points where odour was being generated - the main reason for our being asked to investigate.

The enterprise had grown a great deal with surface channels and a mix-match of drain pipes being laid from each ‘node’ as it had developed. All the pipes ran into one large dam where wastewater was stored and allowed to oxidise prior to being irrigated out over the surrounding pastures. Many of the sewers were not aligned properly, giving rise to surface seepage and most of the inspection covers were not sealed, allowing odour to escape into the atmosphere. Sewage from the various toilets was lead to a variety of septic tanks, all of which were undersized. These also received most of the grey water generated in their node prior to discharging to soak-pits, which again, were totally inadequate and hydraulically overloaded.

The original owner, back in the 17th century, had wisely utilised the poor ground on which to build his house, farm buildings and dam, which luckily for him was on a slight slope but sufficiently far from the nearest natural watercourse to permit water storage and septic sewage systems. Our plan was very simple: separate the sewage into its own system and treat each specific effluent stream individually, prior to combining all the non-sewage streams into the farm slurry dam.

The single (unlined) 550,000 litre slurry dam, which was pushed over 15 years ago and in need of de-sludging and repair, had to be re-plumbed and linked to two more new dams, each 5,000,000 (5,000m3) capacity - approximately 165m long x 25m wide with an average depth of 1.5m - and plastic lined to conform with the local DWAF regulations. This was the most expensive part of the upgrade. However, the dams were stocked with Tilapia and wild water fowl, making them attractive to the visitors as well as affording water storage for summer irrigation.

The shape was important: long and narrow. The wastewater from the primary lagoon flowed into one end of the secondary lagoon, which discharged into the tertiary from its opposite end; ensuring the longest possible ‘residence’ time in both dams. We specified a floating AirMix Aerator on the primary, the position of which could be changed each week by guy lines so that the entire surface could be aerated over a four-week cycle - this also prevented bottom sludge buildup. The secondary became a ‘maturation lagoon’ and the tertiary was for irrigation storage - for which purpose we specified the services of a soils engineer/irrigation consultant who was accredited to all the government authorities.

We advocated using our liquid L2120 to counter odour during the period of drain modifications, which was undertaken by the farm’s competent handyman according to our master plan and direction.

The upgrade protocol

  1. Sewage and septic tanks

    Firstly, we identified all the toilets and redesigned the sewers to gravity the ‘black’ water to one new large septic tank. We based the size of the tank on the number of people estimated to use the facilities on a busy day and added a 50 percent margin. The tank we specified was 40m3 (9m x 3m x 1.5m - actual depth), which was sufficient to handle 2,000lt per day (12 residents at 60lt each per day = 900lt, 5 non-resident staff at 40lt per day = 200lt and 60 guests at 10lt per day = 600lt, giving an actual total of 1,700lt per day with a 300lt per day excess capacity - a further 30 guests). The new soakaway was dug in the sandy loam soil along the contour for a distance of 55m. Provision was made for the possibility of upgrading the system in years to come - the existing septic tank could become an anaerobic digestor for a new small package plant to replace the soakaway.

  2. Winery waste

    This effluent requires specialist treatment so we handed the task to a consultant in the field, who also attended to revision of the Water Management Report for the farm – the winery being the major water consuming fraction of activity. Essentially, the components of the treatment included: solids removal, pH adjustment, aeration, inoculation with BIO-SYSTEMS B560, settlement and drainage to the slurry dam. The effluent quality varied widely from pressing to bottling times, but following treatment the general discharge showed COD values within 120ppm without any odour.

  3. Piggery waste

    The animals were kept in old sties with concrete floors and plastered block-work walls, which drained to the outside where gullies delivered the waste wash water to open ‘drive’ channels. Each pen was washed out periodically and loose straw was used as bedding. This operation required a large quantity of water, pumped back from the slurry dam.

    CH: effluent streams - open drive channel  Open 'drive' channel

    We specified the use of BIO-SYSTEMS HSDG (a cupful per pen per week), which released the ammonia accumulated from the urine that had soaked into the floors and walls causing an offensive porcine reek. We also advocated that BIO-SYSTEMS B800 be sprinkled into the exterior drive channels (75g per channel per week). The semi-treated effluent no longer smelled and flowed to the slurry dam via a vertical Autrex screen, where manure solids were recovered for compost used in the plant nursery. The addition of the B800 greatly benefited the composting process when this manure was mixed with green waste in the windrow heap.

  4. Dairy and cheese wastes

    Here a Rofo 700 grease trap (rated at 4.5lt per second) flowing to a 23m3 [6m x 2.5m x 1.5m] septic tank was used. The dairy floor drained to two gridded surface channels to a gulley with a Rofo 200 floor drain in a line that picked up the three similar floor drains in the cheesery and ran to the exterior grease trap. All cheese curd solids were recovered from the trap baskets and added to the pig feed. The stream was seeded with BIO-SYSEMS B250 once a week (75 grams to the trap and 150 grams in the tank) and this system catered for both the dairy and factory wash water.

    Once a month both floors were pressure cleaned with 1:50 solution of HSDG to prevent the buildup of fats on the tiles and grouting. All the final discharge drained to the slurry dam. Dairy waste is fairly soft and easy to degrade, however, if allowed to age it deteriorates and not only emits a terrible odour but can support nocardia filamentous algae, which cause foaming in the effluent stream (forming a blanket that impedes aeration and is notoriously difficult to eradicate).

  5. Restaurant, butchery and deli

    As they are in the same building, these effluent streams were washed through Rofo 200 floor drains placed at 1 per 9m2 of wet floor space (one per 3m x 3m in the kitchen) combined into one Rofo 700 grease trap. A Rhino Filter was fitted to the kitchen pot wash to reduce loading on the grease trap. 

    The floor drains and the sink wastes are now treated with 20ml and 15ml of DF60 respectively every third day. The grease trap receives 2 x 25g soluble pouches of FogFree 200 once a week. Every night, all floors are mopped down with a 1:20 (5 percent) solution of HSDG, which keeps them squeaky clean and non-slip from fat smitch and spillage.

  6. Slurry dam

    This receives mixed pre-treated effluent (see image below), each stream being of acceptable discharge standard. We fitted an AirMix Aerator to the delivery line of a 0.75kva pump mounted on a tethered raft made from four galvanized oil drums, to circulate the dam’s contents and aerate it at the same time. Every two months, we throw in a cocktail of 1kg comprising 250 grams each of B220R, B250, B800 and B600. However, we have specified that the existing 5,000m3 capacity dam be augmented by two more of a similar size, staggered down the slope. The result will be the conventional ‘three dam’ system, which has proven to work very well in the treatment of wastewater, bringing it in line with DWAF Standard quality (in fact, approaching ‘Special Standard’ quality).

    CH: effluent streams - lagoon before treatment Lagoon before treatment

      Lagoon with Airmix Aerator  CH: effluent streams - lagoon with AirMix Aerator

    Note: rain water is prevented from entering this dam by an earth ‘berm’ constructed on the high side of the slope, which forms a channel directing any storm water run off to the tertiary (water storage) lagoon. In turn this lagoon overflows to the natural watercourse running down the centre of the shallow valley.Solid waste

  7. Solid Waste

    This was a real problem because the waste truck from the rural municipality calls only once every two weeks. We designed a centralized waste area comprising a bunded concrete floor on a slight slope with a 1.8m high lath fence and a motor gate, all under a fly roof, which is 2.2m at the lowest eve and permits cooling draught ventilation. The reduced temperature deters flies and delays the decomposition of organic waste, which had been causing odour. The organic waste is now gathered in 15kg doubled plastic bags and binned in wet waste containers. We allocated various wheeled bins to wet wastes that are sprinkled with 50ml of BIO-SYSTEMS DF60 twice a week.

    Rubbish is collected on a rotational basis and is separated into organic, cardboard and paper, tins, plastics and glass in the ‘waste room’. BIO-SYSTEMS has offered to pressure clean the floor every six months using BIO-SYSTEMS HSDG in 7.5% solution to prevent it from becoming contaminated with fats, usually drippage, that give rise to stale odour and attract cockroaches and flies. We also have plans for them to shred the cardboard, which can be added to the compost in the interests of sustainability. However, care must be taken not to include plastic coated card.

  8. Grey Water

    As with most farms, this one has both surface catchment and borehole (artesian well) supplies. However, as local weather patterns are expected to bring a drier climate in the foreseeable future, they are now recycling most of their domestic grey water.  This is being done by leading it, via a Rhino Filter, to a small sump served by a lift pump – which will shortly run on a solar panel – that delivers it to a 10,000lt plastic ‘treatment tank’ fitted with a Bio-Aqua unit that renders the waste wash water suitable for reusing as toilet flush and for irrigating (via drippers) the plantings close to the public buildings.

    At this stage, there is no ozonization, but should this become necessary, it can be done.

    With the extended roofed area of the various buildings, and depending on weather patterns, there is provision for rainwater harvesting in future. This makes sense because during dry periods ground water becomes increasingly attractive to others, depleting the resource. Coupled with the chance of power cuts, its extraction may also prove unreliable.

    The aforementioned protocol is an economical solution to common effluent problems. However, be warned: the results are only as good as the management of the system.

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