GB2337749A

GB2337749A - A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote the primary productivity in the sea

Info

Publication number: GB2337749A
Application number: GB9912027A
Authority: GB
Inventors: Gang Pan
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-05-28
Filing date: 1999-05-25
Publication date: 1999-12-01
Anticipated expiration: 2019-05-25
Also published as: GB9811362D0; GB2337749B; GB9912027D0

Abstract

A method for simultaneously clearing up harmful algal blooms and hamessing organic pollutants to promote primary productivity in the sea, comprising the steps of sinking the algal cells, organic pollutants and over-enriched nutrients to the bottom sea using iron oxides enriched particles that are modified by cationic reagents, increasing the oxygen content in seawater by adding oxygen sealed in zeolites or bentonite particles, decomposing the organic pollutants in the bottom sea by the added oxidants and catalysts, slowly releasing dissolved iron, phosphate, manganese and nitrogen to the bottom sea from the settled particles, and increasing the ocean absorption of atmospheric carbon dioxide by the added oxygen carriers and the increased primary productivity. Other useful ingredients can also be sent to either surface or bottom seawater by a zeolite or bentonite carrier that carries the needed ingredient in its particles.

Description

1 11 1 2337749 A METHOD FOR SIMULTANEOUSLY CLEARING UP HARMFUL ALGAL

BLOOMS AND HARNESSING ORGANIC POLLUTANTS TO PROMOTE THE PRIMARY PRODUCTIVITY IN THE SEA

The invention is in the field of marine pollution remediation and environmental restoration.

Harmful algal blooms (i.e. red tides) are one type of large marine pollution which can produce toxins that cause massive fish kill and put a serious and recurrent threat to human health, wildlife, marine ecosystems and economy. Current methods that aimed to tackle the red tides include using clay and fatty acid to get rid of red tide', using germanium compound and a herbicide 2, and using hydrogen peroxide to destroy cysts of noxious plankton3. None of these methods was sufficiently potent in natural seawater without also having adverse effects on other organisms. There was no in-situ technique that can destroy pollutants of red tides both in the surface and deep seawaters. There was no technique that can harness the harmful red tides to promote a healthier marine biogeochemical cycling. Using chemical reagents, such as [2] and [3], is not only non-realistic and expensive in large scale in the sea, but also causes other environmental pollution, which can greatly damage marine life and alter the ecological and geochemical cycles in marine environment. The clay method such as [11 may only, in some extent, reduce the red tide algal cells from the surface seawater, but it does not decompose organic pollutants so that the toxins still remain in deep seawater. It is possible for the toxins to be brought up to the surface seawater later. Since clay particles are hydrophilic and negatively Nakanishi, Mildo, 1997, Red tide eliminating composition and method for getting rid of red tide, WO 9738580.

2 UShio; Kazurnichi; Noto; Yoshiki, 1996, Method for preventing emergence of algae and antialgal composition, US patent: 5518990.

3 Egusa; Sywo (Ichikawa, JP); Fukuyo; Yasuo (Matsudo, JP). Method for destroying cyst of noxious plankton. US Patent: 5256423.

1 2 charged in seawater, they do not effectively scavenge most dissolved toxins or organic pollutants. Clay cannot promote primary productivity as dissolved nutrients do. Clay is much less powerful in removing overenriched phosphate and nitrogen in seawater than iron oxides and zeolites do, respectively, which is often a triggering factor for red tides and its re- occurring after the treatment.

The method proposed here involves using a plane or ship to apply a specially composed powder, which consists of iron oxides (1-90%, w/w) coated with cationic reagents (0-20%, wlw) and porous particles such as zeolites or bentonite (1-901/o, w/w) carrying oxygen in their pores, to the algal polluted sea. Depending on the nature of the sea (e.g. whether the sea is limited by nitrogen, phosphate or iron) and the priority purpose of the remediation, the above composed powder can be applied independently or in conjunction with other auxiliary components such as manganese oxides (0-70%, w/w), clay minerals (0-60%) and titanium oxides (030%), in which the inorganic particles may be modified by the cationic reagents or other biodegradable organic matters such as fatty acids (040%) to change their surface properties to be organophilic. The cationic reagents can be inorganic or polymer cationic coagulants, cationic surfactants or cationic flocculants such as ferric chloride, aluminium chloride, biodegradable polymers containing the quaternized nitrogen moirty (e.g. alkyltrimethylammonium ions of chain length ftOM C12 to C20 (C.H2n,IN(CH3)3), tetra-alkylammonium cations, polydiallydimethyl ammonium chloride, and polyethylene imine. A certain flocculants, which can be polyaions, polycations or nonionic polymers (e.g. polyacrylamides, polyacrylates or polyethyleneimines) may be applied to the sea after the application of the above-mention powder. Oxygen can be sealed in the porous zeolites or bentonite by heating the porous zeolites or bentonite in a tank to develop pores, vacuating the air in the closed tank and fulfilling with oxygen as the tank is cooling, moisturising the particles with water moisture in the tank, and finally coating the particles in the tank with a polymer 3 solution such as a cationic reagent, nonionic polymer or polyanion. Most organic pollutants (including algal cells) in the seawater are negatively charged. Iron oxides, among most metal oxides and clay minerals, are the most effective solids that can be pre- modified to be positively charged in seawater. The soluble pollutants (e.g. red tide toxins), particulate algal cells and the over-enriched nutrients can be effectively sunk down to the bottom sea through adsorption, coagulation and flocculation by the added powder. This will not only remove most of the pollutants out of surface water, but also quickly increase the oxygen content in the water that is often oxygen-depleted after the red tides attack. The increased oxygen content in the surface water may in turn increase the ocean absorption of atmospheric C02. Then, some toxic organic pollutants can be decomposed by the oxygen carried in the zeolites or bentonite particles, the iron oxides, and manganese oxides in marine sediment environment (some can be decomposed in water column by titanium oxides and the oxygen). Iron oxides and zeolites are the two cost effective materials that can selectively adsorb phosphate and ammonium ions, respectively. During the decomposition of organic matters and the reduction of iron or manganese oxides in the sediment, dissolved iron, manganese, nitrogen and previously adsorbed phosphate can be released into the deep-sea water. These released nutrients can then be slowly transported to the surface seawater by up-welling current or diffusion to supply continuous new primary productivity, which may increase the ocean absorption Of C02 from the atmosphere.

The principle of the method is to first sink/store the over-enriched organic matters and nutrients to the sediments while quickly increase the oxygen content in the surface water, and secondly, through the slow decomposition of the organic matter and the reduction of iron or manganese oxides in the marine sediments, to slowly and healthily return the nutrients back to the sea. The efficiencies of the settling of the red tides pollutants, the decomposition of the pollutants, the increase of oxygen content in the seawater, the type of nutrients released from the added powders in the sediment and their transportation properties in seawater depend on the 4 composition of the powder applied, in which catalysis at various solid- liquid interfaces (including bacteria in the sediments, and lights and organic matters in the seawater) is essential for some processes to occur. Other useful ingredients can also be sent to either surface or bottom seawater by zeolite or bentonite particles in a similar way.

The method has following advantages:

1) Clear up red tides or eutrophication pollution in surface water (fresh or seawater).

2) Quickly increase oxygen content in the water after the red tide attack.

3) Decompose pollutants/toxins in the sediment.

4) Harness organic pollutants to promote primary productivity.

5) Increase the ocean absorption of atmospheric C02.

6) Promote a heal thier biogeochemical cycling of the nutrients and carbon in the ocean.

7) Cheap and easy to use.

The exact composition of the powder depends on the nature of the sea and the priority purpose of the operation (among the advantages outlined above).

A specific composition, a procedure to prepare a zeolite oxygen carrier and a method to apply the powder to remedy the red tide pollution will be described as an example in which:

The powder is constructed by mixing 40% (w/w) iron oxides, 10% (w/w) ferric chloride, 1 % (w/w) alkyltrimethylarnmonium ions of chain length 18 (C 1 sH37N(CH3)3), 3 Cp/o (w/w) zeolite oxygen carrier, 10% (wlw) manganese oxide and 9% (w/w) tetra-alkylammonium cations modified smectites. Make the powders to have particles size between 1-500pm.

Porous zeolite particles (size 1-50OpLm) are heated to 300 'C, while slowly stirred, in a steel tank. Then, the lid of the tank is closed and the air inside the tank vacuumed. When the tank is cooled to 50 'C, oxygen is fulfilled in the tank. After the particles are cooled to room temperature, a dilute (0.5%) polymer solution of alkyltrimethylammonium is spread on to the particles while they are stirred in the tank. The oxygen is thus "sealed" in the pores of zeolites by the polymer coating. The zeolite oxygen carriers are kept in a closed tank before use. If bentonite is used, it can swell more than 10 times its dry size when wetted by water, holding high concentrated oxygen "solution" in the particles.

An agricultural plane can be used to spread the powder on to the red tides polluted sea. Flocculants such as ferric or aluminium chloride, polyethylene imine, or polyanions (e.g. polyacrylates and polyacrylamides) may be applied using the plane within tens of minutes to hours after the first application of the powder.

The possible wider use and developments of the method will be described in the next two paragraphs. The method described here can also be used to remedy other pollution such as oilrig pollution and eutrophication in coastal or fresh water environments. By increasing the ocean absorption of atmospheric C02 either through increasing the oxygen content or the primary productivity, the method may also be used to tackle the global warming problem. The method of zeolite or bentonite oxygen carriers can also be used to send other ingredients such as nutrients to either surface or bottom seawater for various natural water pollution remediation and fish farming purposes. When the polluted area is not too big, boats or ships that fitted with "flat mouth" funnels can be used to apply the powders. In case of preventing the spread of oilrig pollutants, a closed, double jacket "suspended particle wall" can be formed by applying the powder along routes of circles around the oilrig. After the oilrig is surrounded by the double jacket "suspended particle wall", pollutants discharged from the platform can be largely constrained within the circles, and the seawater outside the particle-circle-wall can be protected from the oilrig pollution.

1 1 6

Claims

CLAIMS:

1. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea, comprising the steps of sinking the algal cells, organic pollutants and over-enriched nutrients to the bottom sea using iron oxides enriched particles that are coated by cationic reagents, increasing the oxygen content in surface water by adding zeolites or bentonite oxygen carriers, decomposing the organic pollutants in the bottom sea by the added oxidants and catalysts, releasing dissolved nutrients to the bottom sea from the settled particles, and increasing the ocean absorption of atmospheric C02 by the added oxygen carriers and the nutrients produced by the method.

2. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea as claimed in Claim 1 wherein zeolite or bentonite oxygen carriers are prepared by heating the porous particles in a tank to develop pores, vacuating the air in the closed tank and fulfilling with oxygen as the tank is cooling, moisturising the particles with water moisture, and finally coating the particles in the tank with a polymer solution such as cationic reagents, nonionic polymers or polyanions.

3. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea as claimed in Claim 1 wherein iron oxide enriched (1-90%, w/w) particles may contain other auxiliary components such as manganese oxides, titanium oxides and clay minerals that may be modified by the cationic reagents.

7

4. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea as claimed in Claim 1, Claim 2 or Claim 3, wherein cationic reagents can be ferric chloride, aluminium chloride, biodegradable polymers containing the quaternized nitrogen moirty such as alkyltrimethylammonium ions of chain length from C12 to C2o, tetra-alkylammonium cations and polydiallydimethyl ammonium chloride.

5. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea as claimed in Claim 1 or Claim 2, wherein zeolites or bentonite carrier method may be used to carry other ingredients such as nutrients to either surface or bottom seawater.

6. A method for simultaneously clearing up harmful algal blooms and harnessing organic pollutants to promote primary productivity in the sea as claimed in claim 1 wherein catalysts include the particle-water interfaces added and the bacteria, lights, organic matters that are existed in the seawater.