3D Printing of Hydrogel Filters Containing Algae Cells for Copper Removal from Contaminated Water

Copper contamination of drinking water and marine areas is detrimental to human health and the environment. Physical and chemical approaches currently used for copper removal from water tend to be expensive and may introduce chemicals to the water. Using suspended algae to remove copper is a biological approach. Its cost is relatively low, and algae can be used for other purposes after being used for copper removal. However, this approach using algae is currently limited in its usefulness due to technological barriers. For example, chemical agents used to remove suspended algae from water after copper is absorbed, can cause secondary contamination. Using immobilized algae instead of suspended algae can overcome these problems. In this preliminary study, hydrogel filters containing algae cells and those containing no algae cells are printed on an extrusion-based 3D printer. They were used in a custom-build filtration setup for copper removal. Experimental results show that hydrogel filters containing algae cells reduced copper concentration in the test solution by about 83% (from 3 to 0.5 ppm) after one hour of filtration, while hydrogel filters containing no algae cells reduced copper concentration in the test solution by about 50% (from 3 to 1.5 ppm) after one hour of filtration.

Hoplonemertean larvae are planktonic predators that capture and devour active animal prey

ABSTRACTThe superficially-simple ciliated planktonic larvae of hoplonemerteans have been assumed to be lecithotrophic direct developers, even though many develop from such small eggs that it is hard to imagine how they could give rise to a viable juvenile without some phase of larval feeding. Indeed, attempts to raise such larvae to settlement without food invariably fail. Observations that some hoplonemertean larvae are found in plankton samples at a range of sizes, and much larger than hatchlings, suggests they must indeed feed somehow. Since these “planuliform” larvae lack apparent means to concentrate suspended algae or other unicellular food, one alternative hypothesis is that they are planktonic predators that hunt large prey. Here we provide direct evidence that this is indeed the case for six distinct species of hoplonemerteans. We recorded wild-caught larvae of Paranemertes californica, Paranemertes sp., Gurjanovella littoralis, Emplectonema viride, Carcinonemertes epialti, and Ototyphlonemertes sp. attacking, subduing, and devouring pelagic crustaceans, including barnacle nauplii, cyprids, copepods and their nauplii, and others. While there is no doubt that some hoplonemerteans are genuine lecithotrophs, our evidence suggests that many species in this group both feed and grow during an extended planktonic larval period. This conclusion has important consequences for biogeographic and life-history studies in this group, because it implies enhanced potential for long-distance dispersal. More broadly, the possibility that many animal larvae are actually carnivores invites reconsideration of prevailing stereotypes about metazoan developmental modes and the trade-offs between them.

Improving the effluent of small wastewater treatment plants by bacteria reduction and nutrient removal with an algal biofilm

In wastewater ponds, bacteria numbers decrease considerably in the case of raised algae concentrations in the effluent. This shows that algae have a high potential for bacteria reduction in wastewater. Simultaneously, algae remove nutrients from the water for the formation of biomass. However, suspended algae also cause a high secondary pollution in the effluent of wastewater treatment plants. By using attached algae, as they are frequently observed as an algal biofilm in the effluent of wastewater treatment plants, the problem of separation of algae and water can be avoided. Furthermore, the algae can be removed simply from the water. In this study the possibilities for bacteria reduction and nutrient removal were examined with the aid of an algal biofilm. The results show that an algal biofilm process can be used for cases where small amounts of wastewater should be treated and a high quality of the effluent should be attained.

Harvesting of Algae from High-Rate Ponds by Flocculation-Flotation

Microalgae grown in stabilization ponds and in high rate oxidation ponds (HROP) treating wastewater, were harvested by flocculation with aluminium sulfate and floated in a laboratory electro-flotation unit, where bubbles were produced electrolytically. It was shown that the higher the solids concentration, the lower is the air: solids ratio needed to achieve 90% algae removal. The simultaneous flocculation of suspended algae and release of bubbles while flocs grow, give equal suspended solids removal as the classical flush mixing flocculation followed by slow mixing-flotation stage. Air : solidsratios between 0.009 and 0.013 were sufficient for flocs flotation by dissolved air flotation (DAF) and electro flotation. Continuous flocculation-flotation in a DAF pilot plant unit showed that flush mixing can be replaced by injection of chemicals in-line provided a retention of 15 sec is given before the inflow to the flotation tank. Slow mixing could be eliminated altogether when bubbles were generated simultaneously with the flocculation stage. DAF was further simplified, replacing the air compressor used for pressuring air into water by a venturi suction at the under pressure side of the pump in the pressurised line. DAF in its simplified version is preferred for algae harvesting in fresh water algae cultures and in HROP systems, while it is recognized that electroflotation may be preferred in harvesting marine microalgae.