• Liquid waste

    To them it's just a crap,
    to us it's bread and butter.

    Spike Milligan

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Non-hazardous biodegradable waste is processed using anaerobic decomposition and converted into biogas (operation R3/R1). 30 tons may be treated daily. Liquid waste is pumped from the storage tank into the hygienisation tank where heaters heat the liquid waste at 70 degrees Celsius for 1 hour. After the hygienisation, the liquid waste is pumped into a separate anaerobic digester of total volume of 1,800 cubic metres.

 

There the aerobic conversion of organic matter into biogas takes place over a period of 30 days at a temperature of approximately 39 degrees Celsius. The first stage involves acid hydrolysis, during which organic matter decomposes into short-chain fatty acids. Then follows the methanogenic phase in which methanogenic bacteria convert the fatty acids into biogas.

 

The resulting biogas is stored in the gasholder while the digested sludge undergoes a mechanical thickening in a centrifuge until the content of dry matter reaches approximately 30 percent. Thickened sludge is stored at the disposal site ready for final disposal. The pumps then transfer the water or centrate, the product of centrifugation, to a storage tank where it undergoes deammonification.

 

Biogas is a mixture of approximately 65 percent of methane, 34 percent of carbon dioxide and 1 percent of other gases. After digestion, the biogas passes from the gasholder through a column containing activated carbon, which removes impurities, such as organic silicon compounds, solvents and sulphide., The biogas is used to fuel biogas engines to produce electricity. The electricity produced covers over 90 percent of the plant's energy needs, and provides all the heat energy required by the wastewater treatment processes. Any excess electricity generated goes back into the electrical grid, while flares dispose of any excess biogas.

Tabel 1:

 

Waste Classfication – List of Waste (operation R3/R1)
Non-hazardous biodegradable waste (hygienisation of liquid waste)

 

Waste Classification List of Waste
02 01 01 sludges from washing and cleaning
02 01 03 plant-tissue waste
02 02 03 materials unsuitable for consumption or processing
02 02 04 sludges from on-site effluent treatment
02 03 01 sludges from washing, cleaning, peeling, centrifuging and separation
02 03 04 materials unsuitable for consumption or processing
02 03 05 sludges from on-site effluent treatment
02 04 03 sludges from on-site effluent treatment
02 05 01 materials unsuitable for consumption or processing
02 05 02 sludges from on-site effluent treatment
02 06 01 materials unsuitable for consumption or processing
02 06 03 sludges from on-site effluent treatment
02 07 01 wastes from washing, cleaning and mechanical reduction of raw materials
02 07 02 wastes from spirits distillation
02 07 04 materials unsuitable for consumption or processing
02 07 05 sludges from on-site effluent treatment
03 03 10 fibre rejects, fibre-, filler- and coating-sludges from mechanical separation
03 03 11 sludges from on-site effluent treatment other than those mentioned in 03 03 10
04 02 20 sludges from on-site effluent treatment other than those mentioned in 04 02 19
07 05 14 solid wastes other than those mentioned in 07 05 13
08 04 10 waste adhesives and sealants other than those mentioned in 08 04 09
08 04 12 adhesive and sealant sludges other than those mentioned in 08 04 11
08 04 14

aqueous sludges containing adhesives or sealants other than those mentioned in 08 04 13

16 03 06 organic wastes other than those mentioned in 16 03 05
19 05 03 off-specification compost
19 06 05 liquor from anaerobic treatment of animal and vegetable waste
19 06 06 digestate from anaerobic treatment of animal and vegetable waste
19 08 05 sludges from treatment of urban waste water
19 08 09 grease and oil mixture from oil/water separation containing only edible oil and fats
19 08 12 sludges from biological treatment of industrial waste water other than those mentioned in 19 08 11
19 08 14 sludges from other treatment of industrial waste water other than those mentioned in 19 08 13
19 09 02 sludges from water clarification
19 09 03 sludges from decarbonation
20 01 08 biodegradable kitchen and canteen waste
20 01 25 edible oil and fat
20 02 01 biodegradable waste
20 03 02 waste from markets
20 03 06 waste from sewage cleaning