Impact of compost process conditions on organic micro pollutant degradation during full scale composting

- Impact of compost O2, N, and moisture on organic pollutant removal investigated.
- Decreased compost O2 level significantly reduces organic micro-pollutant removal.
- Increased N level in the form of ammonium can reduce micro-pollutant removal.
- Typical compost moisture contents do not affect micro-pollutant removal.
- Bench-scale data from non-sterile compost well represent full-scale conditions.

Knowledge about the effects of oxygen concentration, nutrient availability and moisture content on removal of organic micro-pollutants during aerobic composting is at present very limited. Impact of oxygen concentration, readily available nitrogen content (NH4+, NO3−), and moisture content on biological transformation of 15 key organic micro-pollutants during composting, was therefore investigated using bench-scale degradation experiments based on non-sterile compost samples, collected at full-scale composting facilities. In addition, the adequacy of bench-scale composting experiments for representing full-scale composting conditions, was investigated using micro-pollutant concentration measurements from both bench- and full-scale composting experiments. Results showed that lack of oxygen generally prevented transformation of organic micro-pollutants. Increasing readily available nitrogen content from about 50 mg N per 100 g compost to about 140 mg N per 100 g compost actually reduced micro-pollutant transformation, while changes in compost moisture content from 50% to 20% by weight, only had minor influence on micro-pollutant transformation. First-order micro-pollutant degradation rates for 13 organic micro-pollutants were calculated using data from both full- and bench-scale experiments. First-order degradation coefficients for both types of experiments were similar and ranged from 0.02 to 0.03 d−1 on average, indicating that if a proper sampling strategy is employed, bench-scale experiments can be used to represent full-scale composting conditions.