bluewater bio

Is it required to add the bacillus bacteria from time to time?

The HYBACS System grows its own sustained population of Bacillus and does not require any dosing of imported Bacillus, apart from the initial seeding. The design and operation of the HYBACS Process ensures a large and stable population of Bacillus in the biomass.

In contrast, the performance of conventional activated sludge plants may be enhanced by dosing Bacillus spores purchased in barrels from suppliers. However, they are either quickly flushed out of the system or soon die.

It is claimed that process is capable of operating at very low temperatures, such as 6¼C. If so where?

The HYBACS System treats domestic wastewater in Korea at this temperature during winter months. The Nitrogen is removed from the wastewater and compliance with the treatment standard is maintained at this low temperature.

How does the HYBACS process achieve 40% energy reduction in the biological stage?

The HYBACS Process saves energy because the first stage, containing the SMART Units, removes about 40% of the BOD from the wastewater and much of the nitrogen, but consumes comparatively little energy because the aeration is achieved by the rotating lamella. Power consumption in the HYBACS process is 61% of the consumption in the activated sludge plant.

The Phosphorus removal process needs clarification and how it is possible to avoid the P (phosphorus) release in the anaerobic sludge process?

Enhanced (or ‘luxury’) uptake of nitrogen using bacteria groups such as acinetobacter probably does not occur in the HYBACS process. Instead, the Bacillus are thought to be responsible for the uptake. Data from HYBACS operational plants have demonstrated that phosphorus removals of 85% to 90% are obtained from wastewaters with TP/BOD ratios of up to about 4.0 w/w%. Such ratios typify domestic wastewater.

The destruction of sludge solids in digestion tanks releases P. As in conventional A/S treatment, the P released from HYBACS sludge may be precipitated in the sludge or from the dewatering filtrate using a chemical. However, current research suggests that the amount of P released from HYBACS sludge is lower than the amount released from conventional activated sludge because the ‘luxury’ uptake (which is readily released) is not present in HYBACS sludge.

What are the reduced Operating & Maintenance expenses in comparison to the Conventional Activated Sludge process?

The major OPEX savings between the HYBACS Process and the equivalent conventional activated sludge is in the power consumption (see HYBACS comparisons section). The SMART units require minimal maintenance provided the wastewater is adequately screened.

What is the sludge production in the HYBACS compared to the Activated Sludge?

Sludge solids production rates by the HYBACS Process and the Activated Sludge process are about the same. However, the HYBACS process can readily treat unsettled sewage, which reduces sludge solids production rate by eliminating the production of primary sludge solids.

Why is there no odour and are there complaints from neighbours?

Under aerobic conditions, certain Bacillus ssp oxidise hydrogen sulphide and organic sulphides (mercaptans) to elemental sulphur. Such oxidation occurs primarily in the SMART units.

As a result of this oxidation, the SMART units substantially reduce the odour potential of the treatment stream. Whereas the settled sewage may be, the effluent from Stage 1 is normally inoffensive. The HYBACS Process does not generally produce offensive odour emissions at a significant level.

STPs where the HYBACS Process has been retrofitted to an existing installation substantiates this odour reduction. In each case there was a history of complaints from local residents and industry. After the retrofits had been completed, there have been no known complaints.

What are the requirements for discharge to Receiving Water?

The required quality of any particular treated wastewater discharge to a particular receiving water depends on five main factors:

• the level of pollution in the receiving water immediately upstream of the discharge point
• the dilution that the treated wastewater receives in the receiving water
• the oxygenation capacity of the receiving water
• the class of the receiving water, determined by its ecology and the animals that live within it
• the commercial and recreational functions of the receiving water.

The general requirement is that a discharge of treated wastewater should not be significantly detrimental to the quality of the receiving water quality by:

• causing de-oxygenation
• adding toxic pollutants such as ammoniacal compounds.

Where fish (including shellfish) are taken from the receiving water for consumption then the concentration of pathogens in the treated wastewater is another consideration. In practice, mathematical modelling is used to determine discharge requirements.

In Europe, legislation requires that all treated wastewater from populations greater than 2,000 inhabitants should have a BOD less than 25 mg/L. However, local licensing authorities (such as the EA in the UK) may make the quality requirement more stringent - but there is no point in making the quality more stringent than is needed. Each discharge is assessed individually. The idea that all discharges should have the same quality is unscientific and a misapplication of resources. The minimum standard found in the European Urban Waste Water Treatment Directive (1990) is a good starting point.

The environmental impact of discharging treated effluent is a complicated subject and viewpoints vary depending on locality (geography), time periods, etc. However, it seems that the trend is clear that everyone is moving toward lower levels; especially in developed nations. For example, Korea has had BOD=80 at one point but it is moving to 10 by 2008.

Reuse for Irrigation?

Treated wastewater with the BOD of < 20 mg/L is adequate for irrigation, provided it has been oxygenated before discharge. Such treated wastewater will not generally turn septic in typical irrigation distribution pipes, avoiding potential odour nuisance. However, it may be necessary to disinfect the treated wastewater using (for example) chlorine, especially if animals (including humans) come into contact with the water or it is used for irrigating crops that would be eaten raw.

Sludge Disposal?

Sludge may be:

• Dumped in landfill sites
• Recycled to agriculture
• Destroyed by incineration and other thermal methods

In developing countries, landfilling is common because it is the cheapest method, but it is not sustainable. Sludge cake produced by one million people in a year is sufficient to cover a full-sized football field in a pile 18 m deep.

The best disposal method for most communities is to recycle the sludge to agriculture, making use of the fertiliser (nitrogen and phosphorus) value and soil conditioning (organic matter) value. However, the sludge must be treated to safeguard the agricultural workers and consumers. The best method of treatment is digestion from which the biogas can be used for power generation – as in Pastolysis (if included at this stage). Another common treatment method is lime stabilisation, which is expensive now and is becoming more expensive because lime production is energy intensive.

Sludge produced in many large cities in Europe, USA and elsewhere is incinerated. In some cases, energy is recovered from the flue gas. To make incineration cost effective, treatment works need to serving populations of at least 200 000. In the developing world, larger works would be needed. Sludge incinerators required expensive and sophisticated emission pollution control systems and highly trained operators and maintenance engineers.

Wastewater Reuse?

Re-use is a major opportunity for HYBACS plants. However, it is critical to know for what purpose the water re-use is planned / targeted (such as industrial process water, residential grey water or potentially back to drinking water). This will drive how the water is treated and to what level.

Similar to irrigation anything below a BOD of <20 mg/L is suitable for re-use. For example; at BOD 20 mg/L, toilet flushing water use is possible.