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ECO-SOLIDS PROCESS - OPERATIONAL PERFORMANCE
The process results in: - A reduction in sludge volume;
- Improved percentage of solids of the product;
- Complete inactivation of microbiological activity;
- A reduction in volatile solids;
- A reduction in water extractable phosphates;
- A reduction in nitrates;
- A reduction in metals concentration; and
- A reduction in malodours.
These are discussed in more detail below. The table below shows a general summary of the results from the process. Please note that all the results shown here were provided to us following independent tests.Summary of typical results from the Eco-Solids Process
| Item | Feed Material | Treated Material | | Total Solids (%) | 14% | 38% | | Volatile Solids (%) | 66.3% | 13.3% | | VS Reduction (%) | - | 40-90% | | Faecal Coliform (col/g/TS) | >2,200,000 | <10 | | Water Extractable Phosphates (mg/kg) | 4,000-10,000 | <20 | | Metals Concentration Reduction (%) | - | 38% | | pH | 7.3 | 11.7 | | Inlet Temperature (°C) | - | 70 | | Residence Time (mins) | - | 30 |
Note:
a) The results shown here for the feed into the Eco-Solids Process are for the material after de-watering, i.e. as it enters the hopper.
b) The results of the biosolids tested from the discharge of the Eco-Solids Process.Reduction in Sludge Volume - The sludge bulk density is typically increased from 770 kg/m3 to approximately 1,090 kg/m3. This increase in density occurs primarily due to the pressure in the reactor squeezing the void spaces out of the sludge mixture, but also due to the vaporisation of particles as it leaves the reactor. The increase in the density of the material during the process reduces the total volume of the biosolid material. The volume of the Eco-Solid might typically be approximately two-thirds of the original sludge volume, which will provide an equivalent reduction in the disposal transport costs.Improved Percentage Solids - The total percentage solids typically increases by about 10%, e.g. from 14% to 24%, or from 20% to 30%. This 10% increase in percentage solids is due to the addition of lime (~7-8%) and the resulting reduction in water due to the formation of calcium hydroxide (~2-3%).Volatile Solids (%) - 66.3% is the typical amount of the volatile solids (VS) found in the feed results, but would be expected to be nearer 75% in raw sludge. The VS typically reduces to 13.3% (a reduction of 80%) with the Eco-Solids Process. The VS can reduce between 40 and 90% depending upon the VS content of the raw material and the amount of treatment provided prior to the Eco-Solids Process. This reduction in the volatile solids percentage is partly due to dilution from the addition of lime (~25%), but it is primarily due to the volatilisation of and breakdown of organic compounds in the process (~55%), which form complex calcium organo salts etc.pH - The increase in pH is due to the addition of calcium oxide which raises the pH of the biosolid to between a pH of 11 and 12. At a pH of 10.5 ammonia is released from the biosolid, which is contained within the reactor. The release of ammonia raises the pH to 13.3 inside the reactor. When the pressure is released at the end of the reactor, the pH of the biosolid drops back down to 11-12.Faecal Coliform - The <10MPN/g/TS result is the lowest number the labs can typically produce. The reason for such a high reduction is the containment of the ammonia within the enclosed Eco-Solids Process reactor.Phosphate Reduction - Phosphate runoff from the sludge is dramatically reduced as most of the phosphate is transformed from sodium phosphate to calcium phosphate, which provides a log 3 reduction in water extractable phosphates . Tests carried out on sludge samples show that phosphate concentrations are typically 4,000 to 10,000mg/kg. In the treated material the water extractable phosphate is less than 50mg/kg, and is typically less than 20mg/kg. Further benefits on phosphorus are discussed in Section 3.1.Nitrate Reduction - Volatisation and vaporisation of the ammonia compounds from the sludge reduces the total nitrate content of the material by up to 10%, but the concentration of nitrate is further diluted (~30%) by the additional of quicklime and the resultant bulking of the solids. However, restrictions in the agronomic rate at which lime stabilised biosolids can be applied to land do mean that the relative nitrate concentration being applied to the soil, as compared to compost and dried material having a pH of 6-8, are significantly reduced. Further benefits on nitrates are discussed in Section 3.1.Inlet Temperature - The inlet temperature (measured at the inlet of the reactor) is typically 70°C. The introduction of the recycle stream results in a more efficient quicklime reaction.Residence Time - With an inlet temperature of 70°C the minimum required residence time is approximately 30 minutes. The residence time of the biosolid in the reactor can be custom designed to further reduce operating costs.Metals Concentration Reduction - The metals concentration of the sludge is reduced by the addition of lime and the resultant bulking of the solids. However, restrictions in the agronomic rate at which lime stabilised biosolids can be applied to land do mean that the relative metals concentration being applied to the soil, as compared to compost and dried material having a pH of 6-8, are significantly reduced.A Reduction in Malodours - The Eco-Solids Process practically eliminates the malodour normally associated with sewage sludge by managing the ammonia, amines and sulphide odours generated during the process. The odour control is discussed further in Section 2.3.1. | |
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