“Our wastewater lagoon started having algae blooms in 2010, and we did not know any affective solutions until our lagoon engineer attended a presentation by WCS at the Virginia Rural Water Conference in 2011. The engineer had learned that Bio-Domes are not only able to control algae and reduce TSS, but are also the least expensive alternative to solve our lagoon’s problems. After our engineer compared multiple options, we chose Bio-Dome and it was installed in April 2012. The effluent has been within the compliance since then. There are no algae issues. Bio-Dome is very easy to maintain. I highly recommend Bio-Dome for lagoons that have the same problem. “
– Donald Jones, the authority’s administrator and chief operator at Craig-New Castl1. INITIAL PROBLEMS:
Craig-New Castle, VA, had a problem with severe algae blooms in their three-cell wastewater lagoon (Figure 1) during the summer months. These algae caused an increase in the amount of total suspended solids (TSS) in their lagoon’s effluent. Too much TSS can adversely impact water quality and harm aquatic vegetation and aquatic life, so discharge permits usually have very strict TSS limits. Craig-New Castle was looking for an upgrade to meet its permit limit of 30mg/L monthly average TSS.
Figure 1: Satellite imagery of Craig-New Castle Wastewater Lagoon
2. SOLUTION:
Among other update options, the Bio-Dome system was chosen because it was reliable and the most cost-effective alternative. The Bio-Dome system can reduce algae for the following reasons: 1) the airlift action in the Bio-Dome can circulate the algae to into shadows or to the bottom of the lagoon, where they are without sunlight, whereupon the algae will die off and become the organic source for the bacteria inside the Bio-Dome; 2) the fixed-film bacteria in the Bio-Dome out-compete with the algae for nutrients, which are used for cell growth.
From early August to mid-December of 2011, Craig New Castle worked with WCS to run a pilot study in order to test if the process can satisfy the state regulators before the full- scale installation. The results from this pilot study showed the Bio-Dome system was capable of greatly reducing the TSS level lower than the permit limits.
From late March to June 2012, Craig-New Castle proceeded with a full-scale installation of 52 Bio-Domes into pond #3b of the lagoon along with 200,000 floating bird balls (Figure 2). The Bio-Domes started operating with some operational changes in mid-August of 2012. The community was excited by the money they saved for their lagoon’s upgrade in both capital investment as well as operation due to the small amount of energy required for the Bio-Domes.
Figure 2: The Bio-Domes location (upper), 52 bio-domes installed in the pond #3b (lower left-hand corner), and the floating bird balls in the lagoon.
3. RESULTS:
Figure 3 shows the BOD and TSS concentration in the effluent from Jan 2011 to May 2016. Before the Bio-Dome installation (before March 2012), the average effluent BOD and TSS were 16.5mg/L and 25.5mg/L, respectively. There were two months of BOD and four months of TSS exceeded effluent limitation during that time (Figure 3). The effluent BOD and TSS consistently remained lower than the limit since mid-August 2012. The increased performance was mainly due to the loss of algae in the lagoon once the Bio-Domes became fully operational the average effluent concentrations of BOD and TSS decreased to 6.2mg/L and 7.3 mg/L, respectively (Figure 3). Installation of the Bio-Dome system into the Craig-New Castle lagoon, resulted in dramatically reduced TSS and BOD, and successfully maintained compliance with its permit limits with low energy expenditures.
Figure 3: BOD and TSS concentration in the effluent from Jan 2011 to May 2016
