Jarmo Sallanko

Mn(II) removal from groundwater with manganese oxide-coated filter media

Removing soluble manganese from groundwater requires a strong chemical oxidant, such as ozone or potassium permanganate, or raising the pH to alkaline value (over pH 9). Biological or adsorption processes can also be applied. Filter media naturally or industrially coated with manganese oxide are effective in adsorptive manganese removal. In this work, a layer of commercial manganese oxide coated medium was added to the top of an experimental sand/anthracite filter column to improve manganese removal. The coated layer was ca 28 cm thick (20% of the total filter depth) and the sand layer was 110 cm thick. The coated layer enhanced the manganese removal markedly. Manganese removal increased by over 91%, and < 0.02 mg/L of manganese remained in the treated water. Also iron removal was enhanced. Filters with added coated layer recovered faster than reference filter from filter backwashes. Sodium hypochlorite feed, which was tested in regeneration of the filter medium, had a slight negative effect on the filter performance.

Effect of ozonation on treated municipal wastewater

In this study, the effects of ozonation on municipal treated wastewater were investigated. Batch experiments were conducted using two water samples from the same plant: post precipitation plant effluent and the same effluent after a polishing treatment in a wetland. The effects of ozonation on chemical oxygen demand (COD), biological oxygen demand (BOD7), colour and turbidity were investigated. Ozonation with dosages up to 2.7 mg/L substantially decreased the COD of biochemically treated municipal wastewater. One gram of ozone decreased the amount of COD by 1.5 g. With higher dosages, the effectiveness of ozone on COD decreased rapidly. Ozone was a very effective colour and turbidity reducer.

Effects of Ozonation on AOC Content of Humic Finnish Groundwater

The effects of ozonation on assimilable organic carbon (AOC) content of humic groundwater were investigated in batch experiments on three different groundwaters used as drinking water in Finland. All water samples had quite high concentrations of iron (range 2–10 mg/L) and manganese (range 0.1–0.2 mg/L) and therefore combined ozonation and filtration is a possible water purification method. The ozone dosage used varied from 0 to 16.6 mgO3/L (ΔO3/TOC = 0–1.6). The ozone treatment increased the AOC concentration in the groundwater samples to different degrees. For example, an ozone dose of 3.9 mg/L increased the AOC concentration in different water as follows: from 49 μg/L to 55/L, from 7 μg/L to 119 μg/L and from 23 μg/L to 226 μg/L.

Effect of silica on iron oxidation and floc formation

Silicates can greatly affect the characteristics of iron oxidation products, and thereby floc formation, in water treatment. This study investigated the effects of silicate on iron oxidation in six groundwaters from the west coast of Finland. The waters contained 13–29 mg SiO2/L, were soft and acidic, and had high contents of iron, manganese, and organic matter. Sample pH was adjusted to 6.9 or 7.9, and a known concentration, 0–80 mg SiO2/L, of silicate was added. After oxidation with hydrogen peroxide, the sample was filtered to determine the iron size fractions. The results showed that even small amounts of added silicon decreased the iron particle size. The critical silicon:iron molar ratio was 1.3–2.5, above which fine iron particles, <0.1 μm, were formed. Increasing pH weakened the effect of silicon. Addition of silicon did not affect iron that was already in oxidized form.

The Effect of Ozonation on the Size Fractions of Manganese

Manganese is a commonly found substance in groundwater in Finland. As a powerful oxidant, ozone can be used for the oxidizing of manganese even without raising the pH. The SFS (Finnish Standards Association) standard has set the accepted limit for soluble manganese to 0.45 μm. However, some research papers have used the limit of 30 kD (kilodalton) for soluble manganese. This research concentrates on the size fractions of manganese in four samples of untreated groundwater and in four samples of ozonized groundwater when treated with 0.45 μm, 0.20 μm, 100 kD, 30 kD, and 10 kD filters. In all tests, nearly all manganese contained in raw water penetrated all filters. There were slight variations in the flocculation of manganese in ozonized groundwater; nevertheless, hardly any reduction in manganese levels took place beyond 100 kD. After ozonation, there were two water samples which surpassed the manganese limit of 50 μgl−1 set for domestic water when the filtration was 0.20 μm and another two samples when the filtration was 100 kD.

The effect of ozonation on the size fractions of iron and total organic carbon in groundwater.

This paper deals with the size fractions of iron and organic matter in four samples of untreated (raw) and ozonized humus-containing groundwater. The fractionation was made to specify the needed pore size of possible membranes for the removal of oxidated iron and organic material. In the tests, iron contained in two of the raw water samples penetrated all filters almost completely. The iron in ozonized water flocculated somewhat differently in different types of water. In three water samples, the set limit for domestic water was reached after filtration with a 0.20 μ m filter, which was done after ozonation had flocculated the iron. One water sample required a 100 kD filtration.

Effect of ozone and granular activated coal (GAC) on the bioactivity of drinking water

In this research, the appearance of easily biodegradable organic material in ozonation and granular activated coal (GAC) filtration was studied. The amount of bioactivity was measured by conventional AOC analyses used in two different modes and also using quite a new growth potential (GP) method. GAC filtration without ozone doubled the amount of AOC of the chemically treated surface water, whereas by ozonation with GAC filtration it was possible to halve the amount of the AOC. The measurement of GP was noticeably simpler than measuring AOC, but for wider use more parallel studies are needed for the comparability of the results of the analysis.

Dissolved phosphorus levels in fresh municipal wastewater

The influence of wastewater lag-time to the concentrations of dissolved phosphorus was investigated. The dissolved phosphorus levels of fresh municipal wastewater and the rate at which phosphorus dissolves in untreated municipal water was studied. Dissolved phosphorus initially accounted for 34% of total phosphorus in the used water. The level of dissolved phosphorus in wastewater doubled during half a year of storage. The dissolving of phosphorus was most rapid in the first 10 days when dissolved phosphorus levels increased by approximately 1% per day.